Maximum seed germination of Mombasa guinea grass

declined after the second year in cool-storage to levels well

(68%) was reached after 1 year in cool-storage and those of

below 10% and the percentage of dead and empty seeds

Tanzania guinea grass (63%) and Ubon paspalum (85%)

increased rapidly at the same time (Table 3).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

30 M.D. Hare, N. Sutin, S. Phengphet and T. Songsiri

Unscarified Ubon stylo seeds, when treated with acid

germination percentage of unscarified Ubon stylo seeds,

at germination testing, maintained high germination

treated with acid at the time of germination testing, was 3

percentages (>80%) for up to 5 years in both cool- and

times that of seeds acid-scarified following harvest (63 vs.

ambient-storage (Table 4). After 6 years in cool-storage,

21%). Unscarified Ubon stylo seeds still displayed 45%

Table 3. Effects of cool-room (18‒20 ºC and 50% RH) storage conditions on germination of seeds of Mombasa guinea grass, Tanzania guinea grass and Ubon paspalum during 2011‒2017.

Grass

2011

2012

2013

2014

2015

2016

2017

LSD (P≤0.05)

14-day germination (%)

Mombasa guinea grass

35

68

65

27

14

7

0

9.8

Tanzania guinea grass

43

56

63

30

31

12

0

11.1

Ubon paspalum

73

79

85

51

37

7

2

7.2

Fresh ungerminated seeds (%)

Mombasa guinea grass

56

24

3

2

1

0

0

10.7

Tanzania guinea grass

51

36

7

5

3

1

0

12.9

Ubon paspalum

21

14

6

5

3

2

0

4.6

Dead and empty seeds (%)

Mombasa guinea grass

8

8

32

71

85

93

100

10.4

Tanzania guinea grass

6

8

30

65

66

87

100

8.5

Ubon paspalum

6

7

9

44

60

91

98

8.8

Table 4. Effects of storage conditions on germination of seeds of Ubon stylo during 2011‒2017.

2011

2012

2013

2014

2015

2016

2017

LSD (P≤0.05)

Cool-room1

14-day germination (%)

Ubon stylo acid-scarified3

99

95

99

99

95

84

21

5.0

Ubon stylo unscarified4

15

19

23

14

21

19

14

ns

Ubon stylo unscarified, acid with test5

98

99

99

99

97

96

63

5.1

Ambient-room2

Ubon stylo acid-scarified

94

06

Ubon stylo unscarified

10

3

2

1

2

2

3

5.2

Ubon stylo unscarified, acid with test

96

87

93

89

90

84

45

10.7

Cool-room1

Hard ungerminated seeds (%)

Ubon stylo acid-scarified3

1

4

0

0

2

2

0

ns

Ubon stylo unscarified4

85

81

76

84

76

71

7

8.6

Ubon stylo unscarified, acid with test5

2

1

1

1

0

0

0

ns

Ambient-room2

Ubon stylo acid-scarified

6

06

Ubon stylo unscarified

87

88

91

91

89

82

47

3.8

Ubon stylo unscarified, acid with test

3

5

2

5

4

2

3

ns

Cool-room1

Dead seeds (%)

Ubon stylo acid-scarified3

0

1

1

1

3

14

79

5.9

Ubon stylo unscarified4

0

0

1

2

3

10

30

8.5

Ubon stylo unscarified, acid with test5

0

0

0

0

3

4

37

5.3

Ambient-room2

Ubon stylo acid-scarified

0

06

Ubon stylo unscarified

3

9

7

8

9

16

50

6.9

Ubon stylo unscarified, acid with test

1

8

5

6

6

14

52

5.6

118‒20 ºC and 50% RH. 2Range in mean monthly temperatures - minimum 23 ºC, maximum 34 ºC; range in mean monthly RH -

minimum 40%, maximum 92%. 3Scarified in sulphuric acid for 10 min, washed and dried. 4Not treated with acid. 5Scarified with sulphuric acid before germination testing. 6Seeds all dead.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Forage seed germination after 6-yr storage 31

germination after 6 years in ambient-storage, when

centages (Table 2). Dormancy in unscarified Mulato II

treated with acid at the time of germination testing. Ubon

seeds is prolonged compared with that in other Brachiaria

stylo seeds acid-scarified before entry into ambient stor-

species, where dormancy has previously been measured

age, died after 1 year, but in cool-room storage maintained

to last only 10 months in B. decumbens seeds (Grof 1968)

high germinations for 5 years (Table 4). Unscarified seeds

and up to 2 years in B. dictyoneura (now: U. humidicola)

in both cool- and ambient-storage, maintained high levels

seeds (Hopkinson et al. 1996), while dormancy is

(>70%) of hardseededness for up to 5 years (Table 4).

inconsequential in B. ruziziensis (Hopkinson et al. 1996).

Seeds of Ubon stylo maintained high germination

Discussion

percentages (>85%) for up to 5 years when stored in

ambient conditions, but only when they remained

Germination percentages of forage grass seeds stored in a

unscarified (Hare et al. 2014). This indicates that Ubon

cool-room in this study varied substantially after 3 years

stylo seeds should not be scarified following harvest, if

of storage with many below 50% (which we arbitrarily

the aim is to store them for 1 year or more under ambient

define as minimal for sowing to ensure acceptable

conditions. The situation differs in cool-storage, as Ubon

stands). The two guinea grass cultivars lost seed

stylo seeds, both acid-scarified and unscarified,

germination most rapidly to below 50% after 3 years cool-

maintained very high germination levels (>90%) for 4‒5

room storage, while Ubon paspalum seeds maintained

years. Only in the sixth year did germination levels drop,

higher germination for longer and could be kept in cool-

particularly with acid-treated seeds, but they remained at

room storage for up to 4 years before germination

levels above the low-to-zero germination levels of the

percentage dropped below 50%. The most durable grass

grasses. Hardseededness, a type of physical dormancy, in

seed was Mulato II with germination percentage

Ubon stylo seeds was not overcome during either

remaining above 50% for longer than seed of the other

ambient- or cool-room storage and unscarified seeds in

grasses when stored in the cool-room: for 5 years if seed

both storage rooms required treatment with acid each time

was harvested from the ground, but for only 4 years if

a germination test was conducted to overcome

seed was knocked out of the seed head at harvest. After 6

hardseededness.

years in cool-storage seed of all grasses was either dead

The moisture levels in grass seeds stored in the cool-

or had negligible levels of germination.

room varied little from year to year, being above 10% in

We define embryo dormancy as when seeds do not

the first, third and fifth years of storage and 9% or less in

germinate but the embryo inside the seed is viable. We

the second, fourth and sixth years of storage. Since the

determined viability using the TZ assay test as it is the

bags of seeds in the study were moved around within the

quickest test for evaluating seed viability. Embryo

large cool-room, as commercial bags of seeds were

dormancy in seeds of Mombasa and Tanzania guinea

introduced or withdrawn, possible variations in relative

grasses was overcome within 6 months in cool-room

humidity in the room might have caused these moisture

storage (Hare et al. 2014). On the other hand, acid

fluctuations. The seeds were stored in large commercial

scarification at the beginning of seed storage in 2011 was

polyethylene bags and moisture exchange may have taken

required to quickly overcome embryo dormancy of

place. Seed life may have been extended if the seeds were

Mulato II seeds, but with time in cool-room storage,

dried to levels of 8% or less following harvesting and

dormancy persisted and acid-scarified seeds had to be

placed in sealed packages to prevent moisture exchange

retreated with acid each year at the time of testing to get

(Hopkinson and English 2005). However, the purpose of

good germination. This secondary dormancy appears to

the study was to examine the life of our seed lots under

be a physical type of dormancy, similar to that imposed

commercial storage conditions (ambient- and cool-

by the tightly bound lemma and palea glumes over the

storage), so drying the seeds to very low seed moisture

caryopsis of unscarified seeds (Hare et al. 2008). In

levels and packaging them in moisture-proof bags was

unscarified Mulato II seeds, aging in cool-storage did not

considered impractical.

overcome the physical dormancy attributable to these

The results from this study and those from the first

glumes, so seeds had to be acid-scarified at the time of the

study (Hare et al. 2014) have important implications for

germination tests to achieve higher germination per-

the commercial storage and management of pasture seeds,

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

32 M.D. Hare, N. Sutin, S. Phengphet and T. Songsiri

particularly grasses, in the humid tropics. Ideally,

However, the quick deterioration in tropical grass seed

germination levels should be maintained above at least

germination has, to date, not limited the expansion of

60% for 12‒15 months, until seed from the next season is

areas sown to improved pasture species in Southeast Asia

ready for sale. Our first study showed that ambient-

and other humid tropical areas. Farmers may very well be

storage conditions in Thailand, even for a few months,

increasing their seed sowing rates to allow for a possible

were completely unsafe for seeds of our forage grasses,

decrease in germination. Some farmers may also conduct

with a rapid decline in germination percentage to well

their own single germination tests before sowing to

below 50% within 8 months of entering storage (Hare et

calculate seed sowing rates.

al. 2014). Typically, grass seeds in Thailand are harvested

from October to January, cleaned, processed and placed

Acknowledgments

in cool-room storage as soon as possible before the onset

of the hot humid wet season in March. With this quick

We thank Tropical Seeds LLC. for providing financial

entry into cool-room storage, satisfactory germination

support to this study and the Faculty of Agriculture, Ubon

levels (>70%) for most species are maintained prior to the

Ratchathani University for research facilities.

key seed-purchasing period (March‒October). The

exception is Tanzania guinea seed, where it is difficult to

References

obtain germination percentages of 70% under commercial

conditions (60% is considered a satisfactory level).

Grof B. 1968. Viability of seed of Brachiaria decumbens.

Commercial seed lines rarely need to be stored for

Queensland Journal of Agricultural and Animal Sciences

25:149‒152.

longer than 15 months in cool-storage. Conditions in the

Hare MD. 2014. Village-based tropical pasture seed production in

cool-room (18‒20 ºC and 50% RH) we used were satis-

Thailand and Laos – a success story. Tropical Grasslands-

factory for seed storage prior to sale. Hopkinson and

Forrajes Tropicales 2:165‒174. DOI: 10.17138/tgft(2)165-174

English (2005) found that the viability of grass seeds

Hare MD; Tatsapong P; Saipraset K. 2007a. Seed production of

stored at 10 ºC and 50% RH for 6‒8 years remained

two brachiaria cultivars in north-east Thailand. 3. Harvesting

constant. While the temperature in their room remained

method. Tropical Grasslands 41:43‒49. goo.gl/RZjH5K

constant, we tested seeds in a commercial facility, where

Hare MD; Tatsapong P; Phengphet S; Lunpha A. 2007b.

Stylosanthes species in north-east Thailand: Dry matter

both temperature and humidity probably fluctuated (not

yields and seed production. Tropical Grasslands 41:253‒

measured) as the cool-room often remained open for 3

259. goo.gl/SBbFsK

hours at a time to allow forklifts and trollies to enter and

Hare MD; Tatsapong P; Phengphet S. 2008. Effect of storage

either deposit or remove seed.

duration, storage room and bag type on seed germination of

It is important for traders who buy grass seeds (and

Brachiaria hybrid cv. Mulato. Tropical Grasslands 42:224‒

then sell to third parties) to be made aware of the quick

228. goo.gl/Yj2Zio

deterioration in viability of tropical grass seeds in

Hare MD; Phengphet S; Songsiri T; Sutin N; Stern E. 2014.

ambient-storage. They should either sell the seeds within

Germination of tropical forage seeds stored in ambient and

controlled temperature and humidity conditions. Tropical

one month after purchase or, if seed is kept longer, keep

Grasslands-Forrajes Tropicales 2:74‒75. DOI: 10.17138/

it in air-conditioned rooms. Traders, for the most part, do

tgft(2)74-75

not store grass seeds in cool conditions and many do not

Hopkinson JM; Souza FHD de; Diulgheroff S; Ortiz A;

have access to air-conditioned storage rooms. Likewise,

Sánchez M. 1996. Reproductive physiology, seed

farmers should not buy grass seeds until they are almost

production, and seed quality of Brachiaria. In: Miles JW;

ready to sow, unless they have an air-conditioned storage

Maass BL; Valle CB do; Kumble B, eds. Brachiaria:

room. The rapid physiological deterioration of tropical

Biology, agronomy, and improvement. International Center

for Tropical Agriculture (CIAT), Cali, Colombia. p. 124‒

grass seeds also has implications for shipping seeds

140. hdl.handle.net/10568/54362

internationally by sea in containers, as frequently grass

Hopkinson JM; English BH. 2005. Influence of storage

seeds can be in transit by sea for 6‒8 weeks; if hot and

conditions on survival and sowing value of seed of tropical

humid conditions exist, seeds should be shipped in

pasture grasses. 1. Longevity. Tropical Grasslands 39:129‒

refrigerated containers.

139. goo.gl/EnVMZE

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Forage seed germination after 6-yr storage 33

ISTA (International Seed Testing Association). 1993. Inter-

national rules for seed testing. Seed Science & Technology

21, Supplement.

(Received for publication 11 September 2017; accepted 12 January 2018; published 31 January 2018)

© 2018

Tropical Grasslands-Forrajes Tropicales is an open-access journal published by International Center for Tropical Agriculture (CIAT). This work is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Tropical Grasslands-Forrajes Tropicales (2018) Vol. 6(1):34–41 34

DOI: 10.17138/TGFT(6)34-41

Research Paper

Evaluation of growth parameters and forage yield of Sugar Graze

and Jumbo Plus sorghum hybrids under three different spacings

during the maha season in the dry zone of Sri Lanka

Efecto de distancia de siembra en el desarrollo y rendimiento de dos

híbridos de sorgo forrajero (Sugar Graze y Jumbo Plus) durante la

temporada de maha en la zona seca de Sri Lanka

HAJAROOBA GNANAGOBAL AND JEYALINGAWATHANI SINNIAH

Faculty of Agriculture, University of Jaffna, Ariviyal Nagar, Kilinochchi, Sri Lanka. www.agri.jfn.ac.lk

Abstract

A field experiment to evaluate the growth parameters and fodder yields of Sugar Graze and Jumbo Plus under occasional

irrigation was conducted at 3 different plant spacings (30 × 15, 30 × 45 and 30 × 60 cm) on a red-yellow latosol in the

dry zone of Sri Lanka from August 2015 to January 2016. The design was a randomized block with 3 replications. Initial

harvesting of fodder was done 60 days after planting and 2 ratoon yields were assessed at successive 60-day intervals.

Plant spacing was inversely related (P<0.05) to dry matter (DM) yield with the narrowest spacing (30 × 15 cm) producing

yields of 14.1 t DM/ha for Sugar Graze and 12.6 t DM/ha for Jumbo Plus at the initial harvest. Plant spacing also influenced leaf area, stem girth, root length and plant height in the initial harvest. Sugar Graze produced higher yields

than Jumbo Plus at the initial and second ratoon harvests. Yields from ratoon crops were about 30% of those for the

initial harvest. Further studies are needed to determine how these findings apply under the low-rainfall conditions of the

yala season, and chemical analyses and animal feeding studies would provide valuable information on the nutritional value of the different forages.

Keywords: Dry matter yield, forage sorghum, ratoon crop, red yellow latosol, row width.

Resumen

En un latosol rojo-amarillo de la zona seca al norte de Sri Lanka entre agosto de 2015 y enero de 2016 se evaluaron

algunas características de crecimiento y los rendimientos de forraje de los cultivares Sugar Graze y Jumbo Plus bajo

riego ocasional usando 3 distancias de siembra (30 × 15, 30 × 45 y 30 × 60 cm). Los tratamientos se dispusieron en un

diseño de bloque al azar con 3 repeticiones. La primera cosecha de forraje se realizó 60 días después de la siembra,

seguida por 2 cosechas de rebrote a un intervalo de 60 días cada una. Los resultados mostraron que la distancia de siembra se relacionó de manera inversa (P<0.05) con el rendimiento de materia seca (MS), siendo este más alto (14.1 t

MS/ha) en la distancia 30 × 15 cm en la primera cosecha para el cv. Sugar Graze en comparación con el cv. Jumbo Plus

(12.6 t MS/ha). La distancia de siembra también influyó en el área foliar, el grosor del tallo, la longitud de las raíces y la altura de la planta en la primera cosecha. Sugar Graze produjo mayores rendimientos que Jumbo Plus en la primera

cosecha y en la segunda cosecha de rebrote. Los rendimientos en las dos cosechas de rebrote fueron de alrededor del

30% de la primera cosecha. Se requieren estudios adicionales para determinar cómo se comparan estos resultados con

los que se puedan obtener en época seca (temporada yala). Además, análisis químicos y estudios nutricionales con animales proporcionarían información valiosa sobre el valor nutritivo de los diferentes forrajes.

Palabras clave : Distancia entre surcos, latosol amarillo-rojo, rebrote, rendimiento de materia seca.

___________

Correspondence: Dr. (Ms.) Jeyalingawathani Sinniah, Department of

Animal Science, Faculty of Agriculture, University of Jaffna, Ariviyal

Nagar, Kilinochchi, 44000, Sri Lanka.

E-mail: jeyalingawathani@gmail.com

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Yield parameters of forage sorghum hybrids 35

Introduction

cultivars in the dry zone of Sri Lanka are limited. There is

a need to assess the growth of these cultivars and how

High performance of farm animals, especially dairy cows,

varying the plant spacing affects both yield and quality of

depends on the availability of adequate amounts of quality

forage so that the growing demand for forage by livestock

fodder and in developing countries, inadequacy of quality

can be met.

forage is the critical limitation to profitable animal

The present study was designed to determine the crop

production (Sarwar et al. 2002). Among the many options

morphology, growth parameters and forage yield of Sugar

for overcoming the shortage of forage, the introduction of

Graze and Jumbo Plus under irrigation in the dry zone of

high-yielding crop varieties ranks highly (Bilal et al.

Sri Lanka under 3 different plant spacings (30 × 15, 30 ×

2001). However, in many developing countries, because

45 and 30 × 60 cm).

of the ever-growing need for food for humans, only

limited cultivated land can be allocated to produce fodder

Materials and Methods

for livestock. Douglas (1980) recommended annual

summer crops such as forage sorghum hybrids ( Sorghum

This experiment was carried out at the livestock farm,

spp.) for use as alternative forage crops in drier areas in

Department of Animal Science, Faculty of Agriculture,

order to bridge the feed shortage gap.

University of Jaffna, Ariviyal Nagar, Kilinochchi (Figure

Sugar Graze, a sweet sorghum × sweet sorghum

1), from August 2015 to January 2016. These months fall

hybrid , is a popular forage source among the livestock

into Sri Lanka’s maha season, i.e. the period September –

farmers of Sri Lanka and Jumbo Plus, a sweet sorghum ×

February which experiences rainfall through the

Sudan grass hybrid, is still in the initial stages of

Northeast monsoon.

introduction. Sugar Graze is a late-flowering cultivar with

high yields, a crude protein (CP) concentration of 12‒

18% and a high sugar content that boosts feed quality and

palatability, resulting in minimal feed wastage. In

addition, the crop is resistant to a wide range of diseases.

Mature Sugar Graze promotes good weight gains and

provides adequate energy for livestock (Pacific Seeds

2009). Jumbo Plus, a forage sorghum hybrid cultivar, has

excellent re-growth potential and high productivity and is

adapted to both dryland and irrigated situations. It has

similar CP concentration to Sugar Graze with 56‒64% dry

matter (DM) digestibility when the plant is 55‒60 days

old or at 5‒10% flowering stage and can be used for

grazing, silage making and rotational cropping (Forage

Sorghum Guide 2015).

These crops have the potential to compete favorably

with maize silage in terms of yield and nutritive value

(Ketterings et al. 2005) and may be an appropriate

alternative to maize for utilizing irrigation water in

drought-prone areas. The shortage of ground water is the

primary limitation to cultivating grass in the dry zone. As

such, it is essential to select a drought-tolerant grass/fodder

species, and Sri Lankan farmers cultivate fodder sorghum.

In an initial study 7 cuttings were achieved from a single

planting yielding 24 kg of fresh fodder/m2 from a single

cutting with plant spacing of 45 × 15 cm (Sivayoganathan

2016). While research on sorghum cultivars in Pakistan has

shown marked differences between cultivars in green

fodder yield and morphology under 30 cm row spacing

Figure 1. The experimental site, Kilinochchi District, in the

(Bakhsh et al. 2015), similar data on forage sorghum hybrid

dry zone of Sri Lanka.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

36 H. Gnanagobal and J. Sinniah

The remaining period of the year is dry with the driest

done at weekly intervals. Plots were manually weeded at

period being June to August. During the study period

30 days after planting to reduce competition from weeds.

(August 2015‒January 2016), rainfall in individual

Five plants were randomly selected from each plot for

months varied greatly (Figure 2) and due to the extremely

recording of leaf length and width, leaf area [leaf area

low water retention capacity irrigation had to be applied

factor (0.72 for forage sorghum) × length × width] (Arkel

in some months.

1978), number of leaves per plant, stem girth, root length

According to Vavuniya meteorological data, the

from the base of the plant to tip of the selected average

average monthly temperature in the region is 28.4 °C

lengthier rootlet, internodal elongation and plant height at

(range 25.6‒30.0 °C), while maximum and minimum

weekly intervals. At 60 days after planting, on 3 October

averages are 35.0 and 21.3 °C, respectively (Jaffna and

2015, the crops were cut 15 cm from ground level and

Kilinochchi Water Supply and Sanitation Project 2010).

allowed to ratoon. Two ratoon cuts were made at 60-day

Soils of the area are red-yellow latosols (Haplustox),

intervals, on 1 December 2015 and 29 January 2016.

which are the most intensively cultivated soils of Jaffna

Immediately after harvesting, fresh forage was weighed

Peninsula and have very low inherent fertility. Extremely

using a spring balance. Samples (approximately 2 kg) of

poor water retention properties mean that dryland cropping

the harvested forage from each experimental plot were

is inappropriate, while conventional flood irrigation is

selected and air-dried for 24 hours, followed by oven-

impractical owing to very rapid infiltration and soil drying.

drying at 75 °C for 72 h to constant weight for dry matter

The experiment was laid out in a completely

yield determination. Data were subjected to Analysis of

randomized design (CRD) in a factorial arrangement of 3

Variance and mean separation was done with Duncan’s

plant spacings (30 × 15, 30 × 45 and 30 × 60 cm) and 2

multiple range test (P≤0.05) (Duncan 1955) with SPSS

cultivars (Sugar Graze and Jumbo Plus) with 3

(Statistical Package for Social Science) version 16.0 for

replications. Sowing was on 5 August 2015.

Windows.

Results

Initial harvest

For the initial harvest the 2 cultivars generally responded

differently to variation in plant spacing in terms of plant

morphology (Table 1).

While leaf length, leaf width and leaf area were

unaffected by plant spacing for Jumbo Plus, the narrow

spacing (30 × 15 cm) produced narrower leaves with

smaller area than the medium (30 × 45 cm) and wide (30

× 60 cm) spacings for Sugar Graze. Similarly, the narrow

Figure 2. Monthly rainfall of Kilinochchi District from

and wide spacings for Jumbo Plus produced more leaves

January 2015 to February 2016. Source: Department of Census

per plant than the medium spacing, while the medium

and Statistics of Sri Lanka (2015); Kilinochchi District (2016).

spacing for Sugar Graze produced more leaves than the

narrow spacing. In general, the thickest stems were

Within rows spacing was kept constant at 30 cm and

produced at the wide spacing and the thinnest at the

the spacing between rows was varied. Seeds were sown at

narrow spacing.

the rate of 2 seeds per hill and seedlings were thinned to

A similar trend occurred with root length with longer

a single plant per hill 2 weeks after sowing resulting in

root lengths generally being associated with wide plant

plant populations of approximately 222,000, 74,000 and

spacing and shorter root lengths with narrow spacing.

55,000 plants/ha for inter-row spacings of 15, 45 and 60

Plant height was unaffected by spacing for Jumbo Plus,

cm, respectively. Cattle manure was applied at planting at

while the wide spacing for Sugar Graze produced the

the rate of 100 kg/ha (N: 1.2‒1.9%, P: 0.2‒0.5%, K: 0.5‒

tallest plants.

1.1%) and inorganic fertilizers were applied 1 week after

Overall, Sugar Graze displayed slightly longer, wider

establishment of plants at the rate of 50 kg urea, 25 kg

leaves with much greater area than Jumbo Plus but

triple superphosphate and 12.5 kg muriate of potash/ha.

produced fewer leaves, though differences were not

During the dry spell of the study period, irrigation was

significant. This cultivar also produced longer roots than

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Yield parameters of forage sorghum hybrids 37

Table 1. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of Sugar Graze and Jumbo Plus 60

days after planting (initial harvest).

Parameter

Sugar Graze

Jumbo Plus

30 × 15

30 × 45

30 × 60

30 × 15

30 × 45

30 × 60

Leaf length (cm)

90.6 ± 4.92a

91.4 ± 2.17a

92.8 ± 2.69a

86.5 ± 3.52a

89.5 ± 2.19a

87.6 ± 3.11a

Leaf width (cm)

8.6 ± 0.86b

9.2 ± 0.80a

9.2 ± 0.67a

7.27 ± 0.64a

7.37 ± 0.83a

7.15 ± 0.91a

Leaf area (cm2)

560 ± 64.5b

608 ± 61.1a

616 ± 48.8a

443 ± 36.6a

463 ± 66.7a

473 ± 67.9a

Number of leaves/plant

13.0 ± 0.93b

13.9 ± 0.83a

13.3 ± 0.96ab

15.0 ± 0.93a

13.7 ± 0.90b

15.1 ± 1.68a

Stem girth (cm)

5.50 ± 0.38b

6.23 ± 0.86a

6.65 ± 0.62a

5.65 ± 0.52b

6.03± 0.77b

6.57 ± 0.46a

Root length (cm)

23.5 ± 0.01c

28.3 ± 0.01a

26.0 ± 0.01b

22.3 ± 0.01c

24.3 ± 0.01b

25.6 ± 0.01a

Internodal elongation (cm)

21.9 ± 2.54a

20.6 ± 1.95a

21.4 ± 2.41a

20.8 ± 1.77a

22.7 ± 1.16a

23.2 ± 1.95a

Plant height (cm)

227 ± 22.7b

239 ± 40.6b

278 ± 18.5a

290 ± 14.8a

292 ± 14.3a

297 ± 25.4a

Dry matter yield (t/ha)

14.1 ± 2.60a

11.4 ± 1.94b

11.3 ± 1.80b

12.6 ± 2.77a

9.2 ± 2.81ab

6.3 ± 1.71b

Each value is a mean ± SD for 3 replicates.

Within rows and cultivars, means without a common letter differ (P≤0.05).

Jumbo Plus but internodal elongation was greater for

Dry matter yields followed similar trends in both

Jumbo Plus, resulting in taller plants.

cultivars with declining yields as plant spacing increased,

Dry matter (DM) yields were inversely related to plant

but differences were not always significant (Table 2).

spacing with yield decreasing progressively as plant

Varietal differences in DM yield were small.

spacing increased, although differences were not always

significant. Sugar Graze produced higher DM yields than

Second ratoon crop

Jumbo Plus (Table 1).

As for the first ratoon crop, row spacing had no significant

First ratoon crop

effect on leaf width, leaf area and stem girth in either

cultivar, while inconsistent responses occurred for the

In the first ratoon crop some parameters, viz. leaf length,

remaining morphological parameters (Table 3). There were

number of leaves and plant height, were not influenced by

consistent effects of row spacing on DM yields in both

spacing in either cultivar, while leaf width, leaf area,

cultivars with yields declining as plant spacing increased,

internodal elongation and stem girth varied inconsistently

but differences were significant (P<0.05) only for Jumbo

with row spacing in the 2 cultivars (Table 2). Varietal

Plus. Dry matter yields for Jumbo Plus at the medium and

differences also were noted among the morphological

wide spacings declined dramatically to about half those for

parameters of the first ratoon crop, where generally leaf length

Sugar Graze. Overall, increases in row spacing resulted in

and width, leaf area, number of leaves per plant and stem girth

greater percentage yield decreases in Jumbo Plus than in

were greater for Sugar Graze, while Jumbo Plus showed

Sugar Graze. Yields for both ratoon crops were generally

higher values for internodal elongation and plant height.

about 25‒35% of those obtained at the initial harvest.

Table 2. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of first ratoon crop of Sugar Graze and Jumbo Plus.

Parameter

Sugar Graze

Jumbo Plus

30 × 15

30 × 45

30 × 60

30 × 15

30 × 45

30 × 60

Leaf length (cm)

78.3 ± 5.07a

72.7 ± 20.2a

78.1 ± 3.93a

71.3 ± 4.78a

71.4 ± 5.28a

70.0 ± 5.49a

Leaf width (cm)

6.79 ± 0.70a

6.01 ± 0.66b

6.37 ± 0.52ab

4.19 ± 0.41b

4.57 ± 0.34a

4.45 ± 0.49ab

Leaf area (cm2)

382 ± 50.7a

317 ± 100b

358 ± 39.1ab

215 ± 29.4a

234 ± 22.8a

224 ± 35.6a

Number of leaves/plant

9.87 ± 0.83a

9.53 ± 1.25a

10.3 ± 1.03a

9.33 ± 1.18a

9.53 ± 1.13a

8.67 ± 1.50a

Stem girth (cm)

5.15 ± 0.36a

4.45 ± 0.34b

4.63 ± 0.45b

3.83 ± 0.37a

3.88 ± 0.15a

3.63 ± 0.21b

Internodal elongation (cm)

16.1 ± 4.07a

17.8 ± 2.62a

17.5 ± 2.17a

16.9 ± 3.32b

19.6 ± 2.16a

21.1 ± 1.18a

Plant height (cm)

115 ± 19.9a

115 ± 13.0a

119 ± 14.6a

131 ± 15.8a

138 ± 11.6a

139 ± 17.4a

Dry matter yield (t/ha)

3.36 ± 0.531a 2.95 ± 0.614a 2.36 ± 0.416a 3.84 ± 0.511a 3.27 ± 0.309a 2.13 ± 0.483b

Each value is a mean ± SD for 3 replicates.

Within rows and cultivars, means without a common letter differ (P≤0.05).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

38 H. Gnanagobal and J. Sinniah

Table 3. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of second ratoon crop of Sugar Graze and Jumbo Plus.

Parameter

Sugar Graze

Jumbo Plus

30 × 15

30 × 45

30 × 60

30 × 15

30 × 45

30 × 60

Leaf length (cm)

62.7 ± 6.15a

59.0 ± 3.58a

57.5 ± 13.1a

60.7 ± 5.57a

51.5 ± 7.15b

54.5 ± 4.63ab

Leaf width (cm)

5.78 ± 0.78a

5.73 ± 0.82a

5.65 ± 0.98a

3.63 ± 0.47a

3.68 ± 0.62a

4.13 ± 0.38a

Leaf area (cm2)

262 ± 50.7a

244 ± 45.4a

239 ± 89.0a

158 ± 18.5a

137 ± 35.0a

162 ± 21.7a

Number of leaves/plant

7.00 ± 0.63b

7.00 ± 0.01b

8.33 ± 0.52a

6.00 ± 0.63a

6.00 ± 0.63a

6.66 ± 0.82a

Stem girth (cm)

4.50 ± 0.55a

4.25 ± 0.42a

4.08 ± 0.38a

3.17 ± 0.26a

3.20 ± 0.32a

3.36 ± 0.22a

Internodal elongation (cm)

20.0 ± 2.83a

22.1 ± 2.13a

19.0 ± 1.95b

25.2 ± 3.95a

26.7 ± 3.36a

24.4 ± 2.48a

Plant height (cm)

190 ± 17.2a

178 ± 10.2ab

167 ± 10.1b

191 ± 9.12a

182 ± 8.91a

168 ± 9.31b

Dry matter yield (t/ha)

4.47± 0.744a 3.29 ± 1.090a 2.85 ± 0.350a 4.33 ± 0.358a 1.77 ± 0.206b 1.42 ± 0.539b

Each value is a mean ± SD for 3 replicates.

Within rows and cultivars, means without a common letter differ (P≤0.05).

Discussion

(460 ± 58.9 cm2) may be due to differences in genetic

makeup of the cultivars. Musa et al. (1993), Naeem et al.

Leaf length and width

(2002), Mahmud et al. (2003) and Chohan et al. (2003;

2006) also observed variation in leaf area among various

Leaf development has been described extensively for

cultivars and varieties of forage sorghum.

fodders, as growth is mostly reflected in large increases in

leaf length as plants grow to maturity, accompanied by

Number of leaves per plant

relatively small increases in width and thickness (Skinner

and Nelson 1994). Large leaf lengths are also important

The general absence of any consistent effect of row spacing

for the survival of individual plants within a sward (Barre

on leaf number per plant is in agreement with the findings

et al. 2015). Leaf length and width values observed for

of Liu et al. (2004), who observed for maize that it did not

both cultivars during the present study were slightly

affect leaf number. In contrast Lamana (2007) reported that

greater than the values recorded by Singh et al. (2014) for

wider plant spacing in maize had a positive effect on

leaf length (45‒70 cm) and width (4‒7 cm) of sorghum

number of leaves. The values recorded for number of

hybrids. Leaf length of Sugar Graze was similar to the 95

leaves per plant for both cultivars in the present study were

± 2.0 cm reported by Pahuja et al. (2014) in India, for the

consistent with those of Monteiro et al. (2012), who

first cut at 50% flowering and a spacing of 15 × 45 cm,

reported that number of leaves in forage sorghum is

whereas leaf width was slightly higher than that recorded

generally between 14 and 17. Chohan et al. (2003) and

by the same authors (6 ± 0.58 cm).

Naeem et al. (2002) also reported variation among different

cultivars of sorghum for number of leaves per plant.

Leaf area

Stem girth

The results of the present study demonstrate that leaf area

increases as plant spacing increases as shown by Lamana

Stem girth recorded in the present study was similar to

(2007). This could be due to less competition among

that reported by Pahuja et al. (2014) in India for stem girth

plants for space and soil nutrients as the plant population

of Sugar Graze (5.9 ± 0.21 cm at 50% flowering stage and

per unit area decreased. Therefore, the lower population

15 × 45 cm spacing). While Yosef et al. (2009) and Ayub

density which resulted from the wider plant spacing gives

et al. (1999) found significant variation in stem diameter

better conditions for more accumulation of photosynthetic

among different cultivars of sorghum, cultivar differences

products, better growth and expansion of foliage, which

in our study were not statistically significant (P>0.05).

was in turn expressed in greater DM yields. The range of

values for leaf area (440‒615 cm2) for Sugar Graze and

Root length

Jumbo Plus in the present study were in agreement with

the values reported by Nabi et al. (2006) for advanced

The trend for root length to increase as row spacing

lines of forage sorghum cultivars. The higher mean leaf

increased would reflect greater competition between

area in Sugar Graze (595 ± 62.3 cm2) than in Jumbo Plus

plants at the narrower spacings. Despite the shorter root

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Yield parameters of forage sorghum hybrids 39

length per plant at the narrow spacing, the much greater

cultivars. Epasinghe et al . (2012) reported DM yields of

plant populations at this spacing would have resulted in

Sugar Graze in Sri Lanka of 5,230 kg/ha at 60 days after

substantially greater root length per unit area than at the

planting at 45 × 15 cm spacing and these lower yields

wider spacings. As a result plants at the narrow spacing

might be attributed to the differences in the spacing, soil

would have had better opportunity to utilize soil water and

fertility and environmental conditions. By contrast Nabi

nutrients than at wider spacing, resulting in higher DM

et al. (2006) recorded yields of 10,400‒13,100 kg DM/ha

yields.

for advanced lines of forage sorghums and Silungwe

(2011) recorded 13,262 kg DM/ha at 15 cm row spacing

Internodal elongation and plant height

78 days after sowing for Sugar Graze.

Forage yield is a function of growth parameters, viz.

Plant height as a growth parameter is a result of elongation

plant population, plant height, leaf:stem ratio, leaf area,

of the stem internodes, which is influenced by the

and leaf area index (Lamana 2007). The differences in

environment as suggested by Weston (1967). In the current

DM yield between the 2 cultivars could be attributed to

study taller plants were observed with wider spacing,

the fact that Sugar Graze exceeded Jumbo Plus in the

which contrasts with reports in the literature that narrower

growth parameters leaf length and width, leaf area and

spacing will give taller plants as a result of competition for

root length. Watson (1947) has shown that variation in

sunlight (Lamana 2007). However, the absence of any

total dry weight of plants is more dependent on variation

effect of plant spacing on plant height of Jumbo Plus

in leaf area. Light interception capacity of the leaf is

supports the finding of Roy and Biswas (1992) that plant

amplified with the increase in leaf area often leading to

height at maturity was not affected by plant spacing. The

increase in photosynthesis and DM yield. Therefore,

significant differences in plant height between the 2

higher DM yield recorded for Sugar Graze might be

cultivars may be due to genotypic variation, as differences

attributed to its higher leaf area than Jumbo Plus.

in internodal elongation between varieties can lead to

differences in height as reported by Evans (1975) and

First and second ratoon crops

Weston (1967). Nabi et al. (2006) and Silungwe (2011),

who worked with different forage sorghum cultivars, also

The most consistent findings with the ratoon crops were

reported plant heights (203‒230 cm) lower than those in

that there were fewer leaves per plant, leaves were

the present study (227‒298 cm), as did Pahuja et al. (2014)

smaller, height was less and DM yields were lower than

for Sugar Graze (189 ± 1.9 cm) in India.

for the initial harvest. However, DM yield remained a

factor of plant spacing with higher yields at narrower row

Dry matter yield

spacing, indicating that plants were still accessing

moisture and nutrients from the soil in sufficient

Plant spacing has a marked impact on the efficiency of

quantities to maintain acceptable growth levels. The

use of land, light, water and nutrients. By optimizing plant

reduced yields are possibly a function of nutrient supply

spacing, highest yield potential can be achieved from the

in the soil being depleted by the initial crop and a change

smallest possible area (Oseni and Fawusi 1986). The

in seasonal conditions over time. There were no

direct relationship between DM yield and plant

significant differences between Sugar Graze and Jumbo

population agrees with the findings of Fisher and Wilson

Plus in DM yields for the first ratoon crop, in contrast with

(1975), who reported greater DM yield with higher plant

the generally higher yields for Sugar Graze in the initial

populations than with lower plant populations. Wolf et al .

crop and second ratoon crop. Despite having smaller

(1993) and Graybill et al. (1991) also reported that DM

leaves and thinner stems than Sugar Graze, the greater

yield of forage maize responded positively to plant

height of Jumbo Plus ensured that yields in the 2 cultivars

density. This relationship would be affected by the

were similar. The success of the second crop is often a

availability of soil moisture, and the application of

function of how early the main crop was planted and

irrigation on a regular basis in this study would have

harvested, which determines the seasonal conditions

ensured that all row spacings/plant populations had

under which the first and second ratoon crops must grow.

adequate water. Dry matter yield recorded for Sugar

However, normally ratoon crops of sorghum are expected

Graze in the current study seemed to be less affected by

to yield from 25 to 35% of the main crop (Livingston and

differences in row spacing than Jumbo Plus, which

Coffman 1996), and our yields fall within this range.

appeared not to be related to root length as there were no

Significant differences in DM yield between main and

significant differences in root length between the

ratoon crops have been reported by Saberi and Aishah

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

40 H. Gnanagobal and J. Sinniah

(2014), when assessing yield responses of forage ratoon

Duncan DB. 1955. Multiple range and multiple F tests.

sorghum under varying salinity levels and irrigation

Biometrics 11:1–42. DOI: 10.2307/3001478

frequencies.

Epasinghe TM; Jayawardena VP; Premalal GGC. 2012.

Our findings suggest that both Sugar Graze and Jumbo

Comparison of growth, yield and nutritive value of maize,

multi-cut fodder sorghum and hybrid Napier (var. Co3) grown

Plus will grow satisfactorily under irrigation in this

in wet zone of Sri Lanka. In: Kodithuwakku SP; Himali SMC,

environment. While DM yields from the first harvest were

eds. Proceedings of 22nd Annual Students Research Session.

excellent, yields from the ratoon crops were significantly

Department of Animal Science, University of Peradeniya, Sri

lower despite the application of irrigation. A plant spacing

Lanka, 30 November 2012. p. 23. goo.gl/Ri3AFR

of 30 × 15 cm produced the highest yields but results

Evans LT. 1975. The physiological basis of crop yield. In:

under rain-fed conditions would not necessarily be the

Evans LT, ed. Crop physiology, some case histories.

same. Further studies to determine the performance in the

Cambridge University Press, Cambridge, UK. p. 327–335.

low-rainfall ( yala) season are necessary to determine

Fisher KS; Wilson GL. 1975. Studies of grain production in

Sorghum bicolor (L.) Moench. V. Effect of planting density

desirable spacings under such dry conditions. Chemical

on growth and yield. Australian Journal of Agricultural

analyses of forage and digestion studies would provide

Research 26:31–41. DOI: 10.1071/ar9750031

valuable information on the relative merits of these two

Forage Sorghum Guide. 2015. goo.gl/ALg81T (accessed 25

cultivars for livestock feeding.

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© 2018

Tropical Grasslands-Forrajes Tropicales is an open-access journal published by International Center for Tropical Agriculture (CIAT). This work is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Tropical Grasslands-Forrajes Tropicales (2018) Vol. 6(1):42–52 42

DOI: 10.17138/TGFT(6)42-52

Research Paper

Variation in carbohydrate and protein fractions, energy, digestibility

and mineral concentrations in stover of sorghum cultivars

Variación en fracciones de carbohidratos y de proteína, energía, digestibilidad

y concentraciones de minerales en rastrojos de cultivares de sorgo

SULTAN SINGH1, B. VENKTESH BHAT2, G.P. SHUKLA1, KUNWAR. K. SINGH1 AND DEEPIKA. GEHRANA1

1 ICAR-Indian Grassland and Fodder Research Institute, Jhansi, Uttar Pradesh, India. www.igfri.res.in

2 ICAR-Indian Institute of Millet Research, Hyderabad, Telangana, India. www.millets.res.in

Abstract

The nutritional attributes of stover from 11 sorghum cultivars (SP 18005A x 220-2,3,6,7; PC-5; GGUB44 x SSG-59-3;

ICSV-700; CSV-17; NRF-526; FM-1; SPV-1616; PVK-809; UPMC-503; and HC-308), selected on the basis of their

diverse genetic backgrounds and use, were evaluated to aid in selecting parents superior in protein concentration and

digestibility for use in sorghum breeding programs. Samples of stovers were collected after grain harvesting and analyzed. The CP concentrations in different cultivars differed (3.7‒6.7%; P<0.05) as did NDF, ADF, cellulose and lignin concentrations (P<0.05). Total carbohydrate, non-structural carbohydrate and structural carbohydrate

concentrations differed (P<0.05) amongst cultivars as did carbohydrate fractions (CA, CB1, CB2, CC; P<0.05). Protein fractions (PB1, PB2, PB3 and PC) except PA differed (P<0.05). Concentrations of stover protein fractions PA and PB3 were lower than PB1, PB2 and PC. Unavailable protein fraction PC was highest (P<0.05) in stover of SPV-1616 (36.8% CP) and

lowest in ICSV-700 (20.4% CP). Concentrations of gross energy (GE), digestible energy (DE), metabolizable energy

(ME) and total digestible nutrients (TDN) varied (P<0.05) and ICSV-700 had highest concentrations of DE, ME and

TDN (2.60 kcal/g DM, 2.13 kcal/g DM and 59.0%, respectively). Energetic efficiency for maintenance (NEM), lactation

(NEL) and growth (NEG) differed (P<0.05) with ranges of 1.13‒1.42, 0.41‒0.70 and 0.95‒1.33 kcal/g DM, respectively.

Values for estimated DM intake, estimated digestible DM and relative feed value for stovers also varied (P<0.05) with

ranges of 1.76‒2.19%, 55.3‒61.4% and 75.4‒104.1%, respectively. In vitro dry matter digestibility was highest (P<0.05)

for cultivars PVK-809 (55.7%) and ICSV-700 (54.3%). Macro- and micro-mineral concentrations also differed (P<0.05)

across cultivar stovers. The wide genetic variability for nutritional attributes in stovers of sorghum cultivars indicates significant potential for improvement of stover quality through sorghum improvement programs, but care needs to be

taken that grain and stover yields do not suffer.

Keywords : Energy values, nutritive value, sorghum stover, yields.

Resumen

En Hyderabad, India se evaluaron los atributos nutritivos de residuos de cosecha (rastrojo) de 11 cultivares de sorgo de

grano (SP 18005A x 220-2,3,6,7; PC-5; GGUB44 x SSG-59-3; ICSV-700; CSV-17; NRF-526; FM-1; SPV -1616; PVK-

809; UPMC-503; y HC-308), seleccionados por su diversidad genética y formas de uso, con el objeto de identificar líneas parentales superiores por concentración de proteína y digestibilidad, para uso eventual en programas de fitomejoramiento. Las concentraciones de proteína cruda difirieron entre los cultivares (3.7‒6.7%; P<0.05) al igual que las concentraciones de NDF, ADF, celulosa y lignina (P<0.05). También difirieron (P<0.05) las concentraciones de carbohidratos totales, no estructurales y estructurales, y las fracciones de carbohidratos (CA, CB1, CB2, CC). Con excepción de PA, las demás fracciones de proteína (PB1, PB2, PB3 y PC) también difirieron (P<0.05). Las concentraciones de las ___________

Correspondence: Sultan Singh, PAR Division, ICAR-IGFRI, Jhansi

284003, UP, India.

Email: singh.sultan@rediffmail.com

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Nutritional attributes in stover of sorghum cultivars 43

fracciones proteicas PA y PB3 fueron inferiores a PB1, PB2 y PC. La mayor (P<0.05) fracción de proteína no disponible

(PC) se encontró en el rastrojo de SPV-1616 (36.8% CP) y la más baja en ICSV-700 (20.4% CP). Las concentraciones

de energía bruta, energía digestible, energía metabolizable y nutrientes digestibles totales (NDT) variaron entre los cultivares (P<0.05); ICSV-700 presentó las concentraciones más altas de energía digestible y metabolizable, y NDT

(2.60 kcal/g MS, 2.13 kcal/g MS y 59.0%, respectivamente). La eficiencia energética para mantenimiento, lactancia y crecimiento difirieron entre los cultivares (P<0.05) con rangos de 1.13‒1.42, 0.41‒0.70 y 0.95‒1.33 kcal/g de MS, respectivamente. El consumo estimado de MS, la MS digestible estimada y el valor relativo del alimento para los rastrojos también variaron (P<0.05) con rangos de 1.76‒2.19%, 55.3‒61.4% y 75.4‒104.1%, respectivamente. La

digestibilidad in vitro más alta de la MS (P<0.05) se encontró con los cultivares PVK-809 (55.7%) e ICSV-700 (54.3%).

Las concentraciones de macro- y micro-minerales también variaron (P<0.05) entre cultivares. La amplia variabilidad

genética de los atributos nutritivos en los rastrojos de los cultivares de sorgo indica un potencial significativo para mejorar la calidad del rastrojo a través de programas de fitomejoramiento, pero se debe considerar el riesgo de comprometer los rendimientos de grano y rastrojo.

Palabras clave : Calidad nutritiva, rendimientos, valor energético, variabilidad genética.

Introduction

Singh et al. 2014). There is a paucity of systematic

information on nutritive value of improved forage

Sorghum [ Sorghum bicolor (L.) Moench] is one of the

sorghums for ranking of forage cultivars (Akabari and

important cereal crops in the semi-arid tropics globally for

Parmar 2014) and also for selecting genetic material for

providing human food, animal feed and raw materials for

use in sorghum improvement programs.

industrial use. In the present context of global climate

There is a need to quantify the genetic diversity of

change the crop is likely to become more important due to

available sorghum cultivars in terms of nutritive value for

its adaptability to high temperature, water scarcity and

use in breeding sorghum varieties or hybrids with higher

saline conditions (Sanchez et al. 2002; Brouk and Bean

stover value without compromising grain yield (Rattunde

2011). Its tolerance of drought and saline conditions makes

1998; Hash et al. 2000). With this objective, a total of 11

sorghum a valuable feed resource for growing on saline

sorghum cultivars were screened for variability in protein,

soils in arid and semi-arid regions (Fahmy et al. 2010).

carbohydrate and dry matter digestibility to select parents

India contributes 16% of global sorghum production

for subsequent use in sorghum breeding programs.

and traditionally sorghum is grown both as fodder and

grain crops in all states of India, with 3 southern states

Materials and Methods

(Maharashtra, Karnataka and Andhra Pradesh) account-

ing for nearly 75% of sorghum’s cultivable area and 85%

Production, sampling and processing of sorghum stovers

of total sorghum production. It is grown as green fodder

in the rainy season (July to mid-October, Kharif season)

Eleven sorghum cultivars (SP 18005A x 220-2,3,6,7;

and later for grain as a food-feed crop.

PC-5; GGUB44 x SSG-59-3; ICSV-700; CSV-17; NRF-

Apart from producing grain as food for humans plus

526; FM-1; SPV-1616; PVK-809; UPMC-503; and HC-

non-ruminant and ruminant livestock, sorghum residue

308), selected on the basis of diverse genetic

(stover) is an important source of dry roughage for rumi-

backgrounds, use and yield (stover and grain; Table 1)

nants in the tropics, including India. The nutritive value

were grown at the research farm of Indian Institute of

of sorghum stover in terms of protein, energy and di-

Millet Research, Hyderabad, India, in a randomized block

gestibility is low and stover is unable to provide a main-

design with 3 replications in plots of 5 x 4 m spaced at 45

tenance diet for ruminants. In view of the growing impor-

cm between rows and 15 cm between plants within rows.

tance of crop residues for livestock feed, improving the

A basal dose of 80 kg N and 40 kg P/ha was applied, with

nutritive value of sorghum stover is an important object-

a further 40 kg N/ha 30 days after sowing. The variation

tive in the tropics (Rattunde et al. 2001). Blümmel and

in number of days to grain ripening since planting varied

Reddy (2006) reported substantial variation in the fodder

among cultivars: CSV-17 matured in 100 days and ICSV-

value of sorghum stovers and supported the concept of

700 matured in 122 days with the remainder intermediate.

genetic enhancement to improve dual-purpose sorghum

Yields of grain and stover were measured following grain

cultivars. Genetic variability in sorghum for various nutri-

harvesting and a composite stover sample was taken from

tional traits has been reported (Youngquist et al. 1990;

each replication of individual cultivars for chemical

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

44 S. Singh, B. Venktesh Bhat, G.P. Shukla, K.K. Singh and D. Gehrana

analysis. The stover samples were dried in a hot-air oven

the standard method (Licitra et al. 1996). For NDIP and

at 60‒65 ºC for 96 h to constant weight. Dried samples

ADIP, samples extracted with neutral detergent and acid

were then ground through a 1-mm sieve using an

detergent solutions, respectively, were analyzed as

electrically operated Willey mill and subsequently stored

Kjeldahl N x 6.25 using semi-auto analyzer (Kel Plus

in plastic containers for laboratory analysis.

Classic-DX Pelican India). For NPN estimation, samples

were treated with sodium tungstate (0.30 molar) and

Chemical analyses

filtered, and residual nitrogen was determined by the

Kjeldahl procedure. Non-protein nitrogen of the sample

Dry matter (DM), crude protein (CP), ether extract (EE)

was calculated by subtracting residual nitrogen from total

and ash concentrations of sorghum stover samples were

nitrogen. Soluble protein (SP) was estimated by treating

estimated as per procedures of AOAC (2000). Fiber

the samples in borate-phosphate buffer, pH 6.7–6.8,

fractions, namely neutral detergent fiber (NDF), acid

consisting of monosodium phosphate (Na2PO4.H2O) 12.2

detergent fiber (ADF), cellulose and lignin, were

g/L, sodium tetraborate (Na2B4O7.10H2O) 8.91 g/L and

determined following the detergent method of Van Soest et

tertiary butyl alcohol 100 mL/L and freshly prepared 10%

al. (1991) using Fiber Tech analyzer (FibraPlus FES 6,

sodium azide solution (Krishnamoorthy et al. 1983). The

Pelican, Chennai, India). Heat-labile α-amylase and

N estimated in the residue gives the insoluble protein

sodium sulphite were not used in NDF solution. Lignin (sa)

fraction. The SP was calculated by subtracting insoluble

was determined by dissolving cellulose with sulfuric acid

protein from total CP.

in the ADF residue (Van Soest et al. 1991). Cellulose was

estimated as the difference between ADF and lignin (sa) in

Intake, digestibility, energy, feed value

the sequential analysis and hemicellulose was calculated as

difference between NDF and ADF concentrations.

To calculate DM intake (DMI), digestible dry matter

(DDM), relative feed value (RFV), total digestible nutrients

Carbohydrate and protein fractions

(TDN) and net energy (NE) of the stovers for different

animal functions, i.e. lactation (NEL), weight gain (NEG) and

Total carbohydrates (tCHO) of stover samples were

maintenance (NEM), equations given by Undersander et al.

calculated as 100 - (CP + EE + ash). Carbohydrate

(1993) were used. Digestible energy (DE) and net energy

fractions in the samples were estimated as per Cornell Net

(NE) values were calculated using equations of Fonnesbeck

Carbohydrate and Protein (CNCP) system (Sniffen et al.

et al. (1984) and Khalil et al. (1986), respectively. The in

1992), which classifies carbohydrate fractions according

vitro dry matter digestibility (IVDMD) was estimated using

to degradation rate into 4 fractions, viz. CA - rapidly

the 2-stage technique of Tilley and Terry (1963) by

degradable sugars; CB1 - intermediately degradable starch

incubating 0.5 g of sample in inoculum of sheep maintained

and pectin; CB2 - slowly degradable cell wall; and CC -

on a mixed grass hay-concentrate diet.

unavailable/lignin-bound cell wall. Structural carbo-

hydrates (SC) were calculated as the difference between

Minerals

NDF and neutral detergent insoluble protein (NDIP),

while non-structural carbohydrates (NSC) were estimated

Samples of sorghum stovers were wet-digested with 3:1

as the difference between tCHO and SC (Caballero et al.

HNO3:perchloric acid mixture, cooled and filtered

2001). Starch in samples was estimated by extracting

through Whatman 42 filter paper. The aliquot was used

stover samples in 80% ethyl alcohol to solubilize free

for estimation of calcium (Ca), copper (Cu), zinc (Zn),

sugars, lipids, pigments and waxes. The residue rich in

iron (Fe), cobalt (Co) and manganese (Mn) using an

starch was solubilized with perchloric acid and the extract

atomic absorption spectrophotometer (Varian AA 240)

was treated with anthrone-sulfuric acid to determine

against their standards. Phosphorus was estimated colori-

glucose colorimetrically using glucose standard (Sastry et

metrically using Bartor’s reagent according to AOAC

al. 1991). A factor of 0.9 was used to convert glucose into

(2000).

starch (mg %).

The CP of stover samples was partitioned into 5

Statistical analysis

fractions according to the Cornell Net Carbohydrate and

Protein System (CNCPS; Sniffen et al. 1992) as modified

Data were subjected to analysis of variance of SPSS 17.0

by Licitra et al. (1996). Neutral detergent insoluble

to test the differences between sorghum cultivars for

protein (NDIP), acid detergent insoluble protein (ADIP)

chemical composition, carbohydrate and protein fractions,

and non-protein nitrogen (NPN) were estimated following

energy values, digestibility and mineral concentrations.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Nutritional attributes in stover of sorghum cultivars 45

Variable means were compared for significance at P<0.05

Carbohydrate fractions

level (Snedecor and Cochran 1994).

Concentrations of tCHO, NSC and SC of sorghum stovers

Results

differed (P<0.05) between cultivars (Table 3). Total

carbohydrates varied from 88.6% (UPMC-503) to 83.3%

Grain and stover yields

(SP 18005A x 220-2,3,6,7), while structural carbohy-

drates were highest in CSV-17 (66.4%) and lowest in

Stover yields in the various cultivars varied from 7.61 t/ha

ICSV-700 (53.6% DM). Similarly the carbohydrate

(CSV-17) to 13.7 t/ha (SP 18005A x 220-2,3,6,7), while

fractions (CA, CB1, CB2, CC) differed significantly

grain yields ranged from 1.59 t/ha (FM-1) to 4.51 t/ha

(P<0.05) across the sorghum cultivars. The highly

(SPV-1616) (Table 1).

degradable carbohydrate fraction (C

A) was highest

(P<0.05) in stover of ICSV-700 (30.3%) and lowest in

Chemical composition

CSV-17 (16.7%). On the other hand the slowly degrad-

All chemical parameters varied (P<0.05) between

able carbohydrate fraction (CB2) was lowest in ICSV-700

cultivars. Crude protein was highest in SP 18005A x 220-

(53.8%) and highest in CSV-17 (66.4%).

2, 3, 6, 7 and PC5 (6.6 and 6.7%, respectively) and lowest

in UPMC-503 (3.7%; Table 2). The OM and EE

Protein fractions

concentrations in stovers varied (P<0.05), with ranges of

91.0‒93.5% and 1.05‒1.61%, respectively. NDF ranged

The protein fractions PB1, PB2, PB3 and PC differed

from 55.0% (ICSV-700) to 68.2% (CSV-17), ADF from

significantly (P<0.05) in stovers of the sorghum cultivars

35.3% (ICSV-700) to 43.1% (CSV-17), cellulose from

(Table 4). Lignin-bound/unavailable protein fraction PC

27.9% (ICSV-700) to 33.8% (CSV-17) and lignin from

was highest (P<0.05) in stover of SPV-1616 (36.8%) and

4.33% (PVK-809) to 5.79% (CSV-17) (P<0.05).

lowest in ICSV-700 (20.4% CP).

Table 1. Sorghum cultivars used in the study, their use and yields of stover and grain.

Cultivar

Commodity/Major utility

Stover yield (t/ha)

Grain yield (t/ha)

SP 18005A x 220-2,3,6,7

Sweet sorghum/ High biomass

13.7a

2.82cd

PC-5

Fodder

8.96bc

2.23de

GGUB44 x SSG-59-3

Fodder

10.05abc

2.18d

ICSV-700

Sweet sorghum/ High biomass

12.51ab

2.7c

CSV-17

Grain & fodder

7.61c

3.4c

NRF-526

Sweet sorghum/ High biomass

12.07ab

2.46d

FM-1

Fodder

9.49abc

1.59e

SPV-1616

Grain & fodder

11.34abc

4.51a

PVK-809

Grain & fodder

10.76abc

3.89ab

UMPC-503

Fodder

8.6c

2.03de

HC-308

Fodder

9.95abc

1.79e

Means followed by different letters within columns differ significantly at P<0.05 level.

Table 2. Chemical composition (% DM) of stover from 11 sorghum cultivars.

Variable

SP 18005A

PC-5 GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1 SPV-1616 PVK-809 UPMC-503 HC-308 sem

Sig

x 220-2,3,6,7

SSG-59-3

CP

6.6ef

6.71f

5.87de

4.88bc 4.53abc 4.43abc 5.03c

3.87ab

4.46abc

3.68a

4.07ab 0.134 <0.0001

OM

91.5abc

93.1de

93.0de

93.2de 92.6cde 91.9abcd 93.3de

91.1a

91.0a

93.5e

92.4bcde 0.159 <0.0001

EE

1.21ab

1.14ab

1.24ab

1.05a

1.28abc 1.61d

1.51d

1.25ab

1.29cd

1.14ab

1.22ab 0.026 <0.0001

NDF

63.0b

64.0b

62.3b

55.0a

68.2c

62.1b

61.5b

61.7b

62.0b

63.9b

64.1b 0.474 <0.0001

ADF

38.1ab

38.7b

36.8ab

35.3a

43.1c

38.9b

36.2ab

37.0ab

38.0ab

37.7ab

39.0b 0.335 <0.0001

Cellulose

30.3b

31.7b

29.9ab

27.9a

33.8c

30.7b

29.4ab

30.2b

30.8b

31.5b

31.1b 0.251 <0.0001

Hemicellulose

25.5bc

25.6bc

25.5bc

19.7a

25.2bc

23.3b

25.4bc

24.7bc

23.9bc

26.2c

25.1bc 0.286 <0.0001

Lignin

5.51ef

4.84abc

4.48ab

4.96bcde 5.79f

5.58ef 4.73abc 4.54ab

4.33a

4.64abc

5.04bcd 0.074 <0.0001

Means followed by different letters within rows differ significantly at P<0.05 level.

CP - crude protein; OM - organic matter; EE - ether extract; NDF - neutral detergent fiber; ADF - acid detergent fiber.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

46 S. Singh, B. Venktesh Bhat, G.P. Shukla, K.K. Singh and D. Gehrana

Table 3. Carbohydrate and its fractions in stovers of 11 sorghum cultivars.

Variable

SP 18005A x PC-5 GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1 SPV-1616 PVK-809 UPMC-503 HC-308 sem

Sig

220-2,3,6,7

SSG-59-3

tCHO (% DM)

83.3a

84.9ab

85.1ab

86.8cd

86.3bc

85.3ab

86.6cd 85.8abc

84.6abc

88.6d

87.0cd 0.306 0.007

NSC (% DM)

22.7a

23.1a

24.4a

33.2b

19.9a

24.8a

27.6ab

26.1ab

25.7ab

26.5ab

24.8a 0.760 0.102

SC (% DM)

60.7b

61.8bc

60.7b

53.6a

66.4c

60.5b

59.0b

59.7b

58.9b

62.1bc

62.2bc 0.631 0.012

CA (% tCHO)

20.2ab

20.2ab

22.7ab

30.3c

16.7a

21.6ab

24.5bc

20.9ab

21.9ab

21.7ab

20. 9ab 0.744 0.002

CB1 (% tCHO)

0.95a

2.26bc

1.60abc

1.50abc 1.41ab

1.38ab

2.20bc

4.30d

3.57d

3.64d

2.55c 0.188 0.028

CB2 (% tCHO)

62.8b

64.5b

64.0b

53.8a

66.4b

61.1b

59.9b

61.4b

62.2b

61.9b

62.5b 0.680 0.0001

CC (% tCHO)

16.0d

13.0ab

11.7a

14.4bcd 15.5cd

15.9d

13.3abc 13.3ab

12.3ab

12.7ab

14.2bcd 03.05 0.063

Means followed by different letters within rows differ significantly at P<0.05 level.

tCHO - total carbohydrates; NSC – non-structural carbohydrates; SC - structural carbohydrates; CA - rapidly degradable sugars; CB1 -

intermediately degradable starch and pectins; CB2 - slowly degradable cell wall; CC - unavailable/lignin-bound cell wall.

Energy and its efficiency for animal functions

Table 6) with ranges of 1.76‒2.19%, 55.3‒61.4% and

75.4‒104.1%, respectively. In vitro dry matter digestibil-

Energy value in terms of GE, DE, ME and TDN in stovers

ity (IVDMD) of stovers was highest (P<0.05) for cultivars

differed significantly (P<0.05; Table 5). Cultivar ICSV-

PVK-809 (55.7%) and ICSV-700 (54.3%) and lowest for

700 had highest concentrations of DE, ME and TDN (2.60

CSV-17 (40.3%).

kcal/g DM, 2.13 kcal/g DM and 59.0%, respectively),

while CSV-17 had the lowest (2.16 g/kg DM, 1.77 kcal/g

Macro- and micro-minerals

DM and 48.9%, respectively). The energetic efficiency

for different animal functions, viz. NEM, NEG and NEL,

Macro- and micro-mineral concentrations in stovers

also differed (P<0.05) amongst the sorghum cultivars,

differed (P<0.05) across sorghum cultivars (Table 7).

with ranges of 1.13‒1.42, 0.41‒0.70 and 0.95‒1.33 kcal/g

Stover from SPV-1616 had lowest Ca and P

DM, respectively.

concentrations (216 and 39.9 mg/kg, respectively) with

highest Ca in NRF-526 (398 mg/kg) and highest P in HC-

Intake, digestibility and relative feed value

308 (71 mg/kg). The concentrations of micro-minerals,

viz. Cu, Zn, Fe, Mn and Co, ranged between 1.47 and

The calculated values of DMI, DDM and RFV for stovers

9.59, 14.2 and 35.5, 109 and 281, 46.5 and 112.5, and 1.74

of the 11 sorghum cultivars varied significantly (P<0.05;

and 5.44 ug/g, respectively.

Table 4. Protein fractions (% CP) of stovers from 11 sorghum cultivars.

Variable

SP 18005A x

PC-5

GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1

SPV-

PVK- UPMC-503 HC-308 sem

Sig

220-2,3,6,7

SSG-59-3

1616

809

PA

8.95

9.28

6.66

7.73

8.55

6.44

8.49

6.94

11.51

10.29

9.15

0.48 0.661

PB1

26.7ab

26.1ab

21.8a

25.1ab

26.2ab

26.6ab

25.3ab

25.4ab

22.9a

30.0bc

34.1c

0.66 0.010

PB2

33.1bc

30.2abc

36.6c

28.8abc 28.5abc

33.7c

21.4ab 25.0abc

20.9a

21.5ab

20.8a

1.23 0.040

PB3

4.99a

12.93abc 11.30abc

17.96c 12.30abc 12.17abc 16.58bc

5.79a

11.03ab

9.67ab

7.82a

0.854 0.016

PC

26.3ab

21.5a

23.6a

20.4a

24.4a

21.1a

28.3ab

36.8c

33.6bc

28.6ab

28.5ab 0.999 0.002

Means followed by different letters within rows differ significantly at P<0.05 level.

PA - non-protein nitrogen; PB1 - buffer-soluble protein; PB2 - neutral detergent-soluble protein; PB3 - acid detergent-soluble protein; PC -

indigestible protein.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Nutritional attributes in stover of sorghum cultivars 47

Table 5. Energy and energetic efficiency for different animal functions of 11 sorghum stovers.

Variable

SP 18005A x PC-5 GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1 SPV-1616 PVK-809 UPMC-503 HC-308 sem

Sig

220-2,3,6,7

SSG-59-3

GE (kcal/g)

4.17bc

4.01a

4.11abc

4.04ab 4.12abc 4.14abc

4.22c

4.16abc

4.04ab

4.13abc 4.13abc 0.014 0.118

DE (kcal/g)

2.44bc

2.41b

2.52bc

2.60c

2.16a

2.40b

2.55bc

2.50bc

2.44bc

2.46bc

2.39b 0.019 <.0001

ME (kcal/g)

2.00bc

1.90b

2.07bc

2.13c

1.77a

1.97b

2.10bc

2.06bc

2.01bc

2.02bc

1.96b 0.016 <.0001

TDN (%)

55.3bc

54.6b

57.1bc

59.0c

48.9a

54.4b

57.9bc

56.8bc

55.4bc

55.9bc

54.2b 0.437 <.0001

NEL (kcal/g)

1.19bc

1.16b

1.26bc

1.33c

0.95a

1.15b

1.29bc

1.24bc

1.19bc

1.21bc

1.15b 0.016 <.0001

NEG (kcal/g)

0.59bc

0.57b

0.65bc

0.70c

0.41a

0.57b

0.67bc

0.64bc

0.60bc

0.61bc

0.56b 0.013 <.0001

NEM (kcal/g)

1.31bc

1.29b

1.37bc

1.42c

1.13a

1.29b

1.39bc

1.36bc

1.32bc

1.33bc

1.28b 0.0126 <.0001

Means followed by different letters within rows differ significantly at P<0.05 level.

GE - gross energy; DE - digestible energy; ME - metabolizable energy; TDN - total digestible nutrients; NEL - net energy for lactation; NEG - net energy for growth/gain; NEM - net energy for maintenance.

Table 6. Predicted dry matter intake, digestibility and feed value of stovers from 11 different sorghum cultivars.

Variable

SP 18005A x

PC-5 GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1 SPV-1616 PVK-809 UPMC-503 HC-308 sem

sig

220-2,3,6,7

SSG-59-3

IVDMD (%)

51.1cde

47.6bc

52.6def

54.3ef

40.3a

47.7bc

53.7ef

50.9cde

55.7f

48.4bcd

45.7b 0.552 <.0001

DDM (%)

59.2bc

58.7b

60.2bc

61.4bc

55.3a

58.6b

60.7bc

60.1bc

59.3bc

59.5bc

58.5b 0.261 <.0001

DMI (%)

1.89b

1.86ab

1.93b

2.19c

1.76a

1.94b

1.95b

1.95b

1.94b

1.88b

1.87ab 0.015 <.0001

RFV (%)

86.7b

85.1b

90.1b

104.1c

75.4a

88.2b

92.0b

90.9b

89.7b

87.0b

85.0b 1.038 <.0001

Means followed by different letters within rows differ significantly at P<0.05 level.

IVDMD - in vitro dry matter digestibility; DDM - estimated digestible dry matter; DMI - estimated dry matter intake; RFV - relative feed value.

Table 7. Macro- and micro-mineral concentrations in stovers of 11 sorghum cultivars.

Variable

SP 18005A x PC-5 GGUB44 x ICSV-700 CSV-17 NRF-526 FM-1 SPV-1616 PVK-809 UPMC-503 HC-308 sem

Sig

220-2,3,6,7

SSG-59-3

Ca (mg/kg)

343c

236bc

259ab

241ab

341ab

398cd

228bc

216a

215a

241ab

285abc 10.01

0.001

P (mg/kg)

45.9abc

42.3ab

62.6abc

56.4abc 47.9abc 47.2abc 60.7abc 39.9ab

42ab

65.6bc

71c

2.60

0.071

Mg (mg/kg)

58.6

49.8

44.5

46.0

42.9

54.5

52.1

44.9

45.0

42.9

48.6

2.40

0.013

Cu (ug/g)

4.45b

1.86a

1.55a

1.54a

5.45b

8.51c

8.25c

1.47a

2.94a

3.71a

9.59c

1.76

0.032

Zn (ug/g)

14.9

17.2

16.4

27.3

32.2

18.2

14.2

24.5

28.6

35.5

23.8

0.623

0.410

Fe (ug/g)

230ab

277b

281b

195ab

241ab

272b

173ab

149a

164ab

109a

126a

20.17

0.001

Mn (ug/g)

98.3cd

69.2abc

112.5d

68.3abc 54.6ab 71.3abc 54.7ab 74.3abc

83.4bcd

65.0abc

46.5a

3.94

0.011

Co (ug/g)

3.86abc

3.06abc

4.30bc

3.50abc 3.04abc 4.85bc

1.74a

3.05abc

2.57ab

4.25bc

5.44c 0.258

0.026

Means followed by different letters within rows differ significantly at P<0.05 level.

Discussion

fodder yields and biomass, and hence better suited as a

dual purpose sorghum variety. Sharma (2013) observed

Grain and stover yields

that CSV 17 was a good grain yielding variety that had

least stover yield in western Rajasthan, India.

The stover yields of high biomass lines SP 18005A x 220-

2,3,6,7, ICSV-700 and NRF-526 were higher, but not

Chemical composition

significantly so, than those of fodder and grain types SPV-

1616 and PVK-809. This is expected because the high

Cereal stovers and straws are usually low in crude protein

biomass lines were specially bred for higher biomass. On

and rich in fiber concentrations, unable even to meet the

the other hand, the grain yields were higher in SPV-1616

minimum CP requirements (7%) for maintenance of

and PVK-809 followed by CSV-17. The former two

animals and rumen microbes (Minson 1990), so there is

varieties were bred for maximizing grain yield with

need to supplement these stovers with protein rich

superior stover yield. Umakanth et al. (2012) observed

leguminous forage or non-protein nitrogen or protein

that SPV 1616 showed high adaptability for grain and

sources. In the present study CP concentrations (3.7‒

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

48 S. Singh, B. Venktesh Bhat, G.P. Shukla, K.K. Singh and D. Gehrana

6.7%) of sorghum stovers are below the maintenance

fraction. Carvalho et al. (2007) reported that NDF concen-

requirement for ruminants. Mativavarira et al. (2013)

tration influences carbohydrate fraction CB2 and forages

reported that CP concentrations of stovers varied (P<0.05)

high in NDF concentration usually have higher values of

across cultivars and ranged between 5.6 and 6.6%, which

CB2. Values of carbohydrate fraction CC in our study

supports our findings. Varietal differences for sorghum

(11.7‒16.0 % tCHO) were generally lower than the 15.8‒

stover quality have been reported for protein and cell wall

25.2% reported by Malafaia et al. (1998) for grasses.

concentrations (Badve et al. 1993). Fiber fractions, viz.

Protein fractions (PB1, PB2, PB3 and PC) differed

NDF, ADF, cellulose and lignin, are in general agreement

(P<0.05) across sorghum cultivars, which may be

with the earlier recorded values of Elseed et al. (2007)

attributed to differences in concentrations of CP and

across 5 sorghum varieties. Crude protein, OM and EE

lignin. About 5‒15% of total forage N is bound to lignin,

concentrations of sorghum stovers reported by Misra et

or rather, is unavailable to ruminal microorganisms (Van

al. (2009) were on par with our results, while their NDF

Soest 1994). Protein fraction PC of stovers recorded in our

and ADF concentrations were higher than our values.

study ranged between 20.4 and 36.8% CP, exceeding the

Like the present study, variability in NDF, ADF, cellulose

above levels, probably due to variability in lignin

and lignin concentrations of sorghum stovers in different

concentrations. Forages, fermented grains and byproduct

cultivars has been reported earlier (Garg et al. 2012;

feeds contain significant amounts of fraction PB3

Hamed et al. 2015).

(Krishnamoorthy et al. 1983).

Carbohydrate and protein fractions

Energy and its efficiency

Carbohydrates constitute the main energy source of plants

Energy density of roughages is a primary parameter

(50‒80%) and play an important role in animal nutrition

influencing animal productivity. Stovers from the

as a prime source of energy for rumen microorganisms

evaluated sorghum cultivars had adequate energy, except

(Van Soest 1994). In our study total carbohydrate

for CSV17 (ME 1.77 kcal/g), to meet the maintenance

concentrations of sorghum stovers varied between 83.4

requirement of livestock (ME 2.0 kcal/g DM recom-

and 88.6% DM, and exceeded the 78.5% DM reported by

mended for ruminants; ICAR 2013). The DE and ME

Das et al. (2015). Carbohydrate accumulation in fodder

concentrations in our study differed (P<0.05) across

crops is influenced by several factors like plant species,

cultivars, being highest for ICSV-700 (2.60 and 2.13

variety, growth stage and environmental conditions

kcal/g DM) and lowest for CSV-17 (2.16 and 1.77 kcal/g

during growth (Buxton and Fales 1994). Concentrations

DM). The range of values for DE (2.16‒2.6 kcal/g DM)

of SC and NSC differed (P<0.05) across the cultivars as

and ME (1.77‒2.13 kcal/g DM) are similar to the 2.14‒

suggested by Ferraris and Charles-Edwards (1986) and

2.51 kcal DE/g DM and 1.76‒2.05 kcal ME/g DM

McBee and Miller (1990). Swarna et al. (2015), while

recorded by Neumann et al. (2002), the 1.70‒2.00 kcal

evaluating the nutritive value of crop residues, found that

ME/g DM reported by Garg et al. (2012) and the 1.6‒1.72

CA, CB1, CB2 and Cc concentrations in sorghum stover

kcal ME/g DM reported by Mativavarira et al. (2013). The

were 14.7, 1.12, 56.8 and 28.0% of tCHO levels, a pattern

variation in TDN concentrations in our study (59.0% for

of carbohydrate fractions identical with our results. Rela-

ICSV-700 to 48.9% for CSV-17) is a function of

tively low CC values (11.7‒16.0% tCHO) in our study

differences in fiber concentrations, as fiber is often used

may be due to the lower lignin concentrations in our

as a negative index of nutritive value in the prediction of

stovers than in theirs. In our results carbohydrate fraction

total digestible nutrients and net energy. Sorghum stover

CB2 was highest in CSV-17 (66.4%) and lowest in ICSV-

TDN concentrations of 46.5‒56.5% reported by Garg et

700 (53.8% tCHO). This is probably a function of the

al. (2012) cover a similar range to our findings, while

higher NDF and hemicellulose concentrations in CSV-17

Beef Magazine (2015) suggests TDN concentrations of

and lower NDF and hemicellulose concentrations in

sorghum stover are about 54% and Neumann et al. (2002)

ICSV-700. This was substantiated by the fact that forage

reported TDN of silage made from sorghum hybrids

with high NDF levels had higher concentrations of the CB2

between 54.4 and 62.2%. Studies on the net energy

fraction, which is more slowly degraded in the rumen,

efficiency of sorghum stovers for animal production

impacting microbial synthesis and animal performance

functions is limited and values for NEM, NEG and NEL

(Ribeiro et al. 2001). Higher hemicellulose concentrations

reported in Beef Magazine (2015) for sorghum stover of

result in higher concentrations of carbohydrate CB2

1.06, 0.40 and 1.06 kcal/g DM corroborate our results.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Nutritional attributes in stover of sorghum cultivars 49

Mean values of NEM, NEG and NEL reported by Bean et

Macro- and micro-minerals

al. (2011) for hay made from the second cut of 32

sorghum hybrids were 1.13, 0.59 and 1.21 kcal/g DM, i.e.

Forages neither contain all the required minerals nor are

within the range of energy values for sorghum stovers

they present in adequate quantity to meet animal

recorded in our study.

requirements (Vargas and McDowell 1997). Calcium and

phosphorus constitute the major portion (up to 70%) of

Intake, digestibility and relative feed value

the body’s total mineral elements, play a vital role in

almost all tissues in the body and must be available to

From a livestock production view point, intake and

livestock in proper quantities and ratio (McDowell et al.

digestibility are the main criteria in breeding programs for

1993). The Ca concentrations that we found, 215‒343

quality improvement in most cereal fodder crops. Dietary

mg/kg, should fulfill the maintenance requirements of

ruminants (270‒570 mg/kg;

fiber concentration, its digestibility and rate of degradation

NRC 2001), but P and Mg

concentrations in stovers were low (39.9‒71 and 42.9‒

in the rumen are the most important forage characteristics

58.6 mg/kg) and unable to meet the critical levels (220

that determine DMI (Roche et al. 2008). The differences in

predicted DMI levels we recorded (1.76‒2.19%) may be

and 120‒220 mg/kg) recommended for ruminants. While

the Ca concentrations in sorghum stover/straws reported

attributed to differences in NDF concentrations. The NDF

by Ramesh et al. (2014) and Garg et al. (2003) are more

concentration of CSV-17 was 68.2%, which exceeds the

or less similar to our values, P concentrations reported by

60.0% usually considered as the threshold likely to

these workers are higher than our values. Misra et al.

significantly reduce intake in ruminants (Zewdu 2005).

(2015) reported P and Mg concentrations in sorghum

Mahanta and Pachauri (2005) recorded DMI between 1.84

stovers (N = 31) similar to ours. The concentrations of Cu

and 2.55% for sheep fed silage from 3 sorghum cultivars

(1.47-9.59 ug/g), Zn (14.2-35.5 ug/g) and Fe (109-281

ad lib. Relative feed value of hay from second cut of 32

ug/g) recorded in our study were within sorghum stover

sorghum hybrids ranged between 106 and 126 (Bean et al.

values reported by Ramesh et al. (2014) and Misra et al.

2011), which exceeded the 75.4‒100 we recorded. We

(2015). The low concentrations of many minerals in

attribute the lower RFV of stovers in the present study to

straws and stovers are probably due to maturity and

their lower quality relative to the whole plants examined at

possible transfer of nutrients to seeds. Mineral

a younger age by Bean et al. (2011), i.e. higher NDF and

concentrations in feeds and fodders are influenced by a

ADF concentrations as these influence the intake and

number of factors (soil pH, soil type, plant species, stage

digestibility of a fodder. Forage containing 41% ADF and

of growth and harvest, crop yield, intensity of agriculture

53% NDF is considered to have an RFV of 100 and RFV

system, climate, fertilizer rate etc. (British Geological

values decrease as the concentrations of NDF and ADF

Survey 1992; McDowell et al. 1993).

increase with crop maturity.

The results from this study revealed significant

The variability in digestibility values may be attributed

variability in apparent nutritive value of the sorghum

to differences in cell wall concentrations. Elseed et al.

stovers tested. This indicates that there is considerable

(2007) reported effective degradability of dry matter of

potential for selecting appropriate genotypes to include in

stovers from different cultivars between 44.4 and 67.7%,

breeding programs to improve stover quality. While

which covers a similar range to our IVDMD and DDM

stovers of all genotypes had adequate energy to meet

values. Bani et al . (2007) recorded an inverse relationship

ruminant maintenance requirements, protein concen-

between forage fiber fractions and DM digestibility, while

trations were low and quite variable. While there is

Barriere et al. (2003) and Seven and Cerci (2006)

potential to improve stover quality by breeding, care

indicated that nitrogen concentration and cell wall poly-

would need to be taken to ensure grain and stover yields

saccharides determine the digestibility of a crop. The

did not suffer as a result. Feeding studies with animals

IVDMD of sorghum stover of 53.3% reported by Misra et

would throw more light on the predicted feed intakes and

al (2009) is consistent with our stover IVDMD values.

digestible dry matter values reported in this study.

The lower concentrations of NDF, cellulose and lignin in

ICSV-700 and FM-1 could explain their higher IVDMD

Acknowledgments

and DDM values (Tovar-Gomez et al. 1997; Zerbini and

Thomas 2003), while the highest lignin concentration

Authors are thankful to Department of Biotechnology for

(5.79%) in stover of sorghum cultivar CSV-17 may

providing financial assistance to carry out this research

explain the lowest IVDMD and DDM values for this

work. Thanks to Director, Millet Research Institute,

cultivar.

Hyderabad and Director, Indian Grassland and Fodder

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

50 S. Singh, B. Venktesh Bhat, G.P. Shukla, K.K. Singh and D. Gehrana

Research Institute, Jhansi for providing facilities for

Das LK; Kundu SS; Kumar D; Datt C. 2015. Fractionation of

conducting this work.

carbohydrate and protein content of some forage feeds of

ruminants for nutritive evaluation. Veterinary World 8:197–

202. DOI: 10.14202/vetworld.2015.197-202

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Tropical Grasslands-Forrajes Tropicales is an open-access journal published by International Center for Tropical Agriculture (CIAT). This work is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Tropical Grasslands-Forrajes Tropicales (2018) Vol. 6(1):53–57 53

DOI: 10.17138/TGFT(6)53-57

Comunicación breve

Evaluación de un sistema de manejo de Axonopus catarinensis en

rotación basado en el remanente de forraje no pastado (Renopa)

Long-term assessment of a new rotational-grazing management strategy

called PUP-grazing (proportion of un-grazed pasture)

DANIEL R. PAVETTI1, MARCELO A. BENVENUTTI2, ÓSCAR RADKE1 Y ÓMAR A. CIBILS1

1 Instituto Nacional de Tecnología Agropecuaria (INTA), EEA Cerro Azul, Misiones, Argentina. www.inta.gob.ar

2 Department of Agriculture and Fisheries, The University of Queensland, Brisbane, Australia. www.daf.qld.gov.au

Resumen

Una nueva estrategia de pastoreo rotativo – Renopa (remanente no pastado) – fue comparada productiva y

económicamente con el pastoreo rotativo tradicional (PRT) en pasturas de Axonopus catarinensis durante dos periodos (2013/14 y 2015/16) en la provincia de Misiones, Argentina, utilizando terneros de cruza Cebú. El promedio del remanente no pastado del Renopa y el PRT fue 11.5 y 3.4% del área de pastura, respectivamente. La ganancia diaria de

peso fue significativamente más alta (P<0.05) para el Renopa que para el PRT (606 vs. 420 g/día). La ganancia de peso

por hectárea también fue 35% más alta para el Renopa (194 vs. 144 kg/ha por periodo). El ingreso bruto por hectárea

fue mucho más alto para el Renopa (US$ 85.7 vs. 8.4/ha por periodo). Concluimos que el Renopa tiene un alto potencial

para mejorar la productividad de pasturas de A. catarinensis.

Palabras clave : Consumo de forraje, ganado vacuno, ganancia de peso, manejo del pastoreo, margen bruto.

Abstract

A new rotational-grazing management strategy called PUP-grazing (proportion of un-grazed pasture, which is the estimated percentage of pasture vegetation without signs of being consumed) was compared with the traditional rotational-grazing management strategy (TGMS, which is based on residual sward height) using Brahman cross steers

on Axonopus catarinensis over two periods (2013/14 and 2015/16) in Misiones, Argentina. The proportion of un-grazed pasture for PUP and TGMS was 11.5 and 3.4%, respectively, of the pasture area. Average daily liveweight gain/animal

was significantly higher for PUP than for TGMS (606 vs. 420 g/d; P<0.05) while liveweight gain per hectare was 35%

greater for PUP (194 vs. 144 kg/ha/period). The gross margin per hectare was much higher for PUP than for TGMS

(US$ 85.7 vs. 8.4/ha/period). These results indicate that on A. catarinensis pastures PUP-grazing has the potential for greater animal and economic performance than the TGMS.

Keywords : Cattle, forage consumption, grazing management, gross margin, liveweight gain.

___________

Correspondencia: Marcelo Benvenutti, Department of Agriculture

and Fisheries, The University of Queensland, Gatton Campus, John

Mahon Building 8105, Lawes Qld 4343, Australia.

Correo electrónico: Marcelo.Benvenutti@daf.qld.gov.au

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

54 D.R. Pavetti, M.A. Benvenutti, O. Radke y O.A. Cibils

Introducción

cada una de ellas en ocho subpotreros de 1,250 m2 cada

uno. En una de las partes se tomaron las observaciones

Una práctica de manejo común en sistemas de pastoreo

con el sistema Renopa y en la otra con el PRT. Los

rotativo consiste en asignar la permanencia de los

animales entraron a cada tratamiento el 6 de noviembre

animales en potreros en función de la altura del forraje

de 2013, con pesos promedio de 194± 2.6 kg y 190± 3.2

residual. No obstante esta estrategia es limitada por el

kg para el Renopa y el PRT, respectivamente. Las

hecho que la altura residual a la cual el consumo de forraje

evaluaciones se hicieron durante un periodo de 105 días.

y la respuesta animal decrecen depende no solo de la

En el sistema PRT los animales fueron cambiados de

especie de pastura sino también de la altura al comienzo

subpotrero cuando por efecto del consumo animal, la

del pastoreo (Benvenutti et al. 2016; 2017).

pastura alcanzó una altura promedio en 28 mediciones

Benvenutti et al. (2016; 2017) en pasturas del pasto

diarias de 20 cm sobre el nivel del suelo.

Jesuita Gigante ( Axonopus catarinensis) en un sistema de

En el caso del Renopa los animales fueron cambiados

rotación y en caña de azúcar, encontraron que aplicando el

de potrero cuando el porcentaje del remanente de pastura

criterio del forraje remanente no-pastado (Renopa) mejoró

fue aproximadamente el 10% del total del área del

el consumo de forraje por bovinos en pasturas con

subpotrero. Para ello cada día se hicieron mediciones en

diferentes alturas. En estos trabajos se encontró que al

dos transectos diagonales y se contaron el número de

comienzo del periodo de ocupación los animales

pasos realizados sobre pastura no pastada (Foto 1).

alcanzaron el mayor nivel de consumo diario de forraje

Cuando este número estuvo entre 5 y el 10% del total de

especialmente en el estrato superior de hojas de la pastura.

pasos se procedió al cambio del subpotrero. Por ejemplo,

El consumo se redujo cuando más del 90% de la superficie

si el total de pasos en ambas diagonales fue de 200, y se

de la pastura fue defoliada por primera vez, debido a que

registraron entre 10 y 20 pasos en sitios no pastados, los

los animales no tuvieron otra opción que consumir el

animales fueron cambiados de potrero.

estrato inferior de esta de menor calidad con alta

proporción de tallos y material senescente. Con base en esta

observación se determinó que el mejor indicador para el

cambio de potrero de los animales sin pérdida de consumo

de forraje era la proporción del remanente no-pastado, la

cual fue equivalente entre el 5 y 10% del total del área del

potrero, independiente de la especie de pastura y la altura

al comienzo del pastoreo (Benvenutti et al. 2016; 2017).

Este remanente estuvo normalmente asociado con sectores

de la pastura contaminados por heces.

Tomando como base las observaciones anteriores,

durante dos periodos, 2013/14 y 2015/16, en Misiones,

Argentina, en un experimento de más largo plazo,

utilizando variables productivas y económicas, se evalúo

Foto 1. Área experimental de Axonopus catarinensis en un

el sistema Renopa con el objeto de determinar si el mayor

sistema silvopastoril con Pinus taeda, con sectores pastados y

consumo de forraje observado resulta en una mayor

no pastados.

respuesta productiva y económica, cuando se compara

con el pastoreo rotativo tradicional (PRT).

Utilizando un septómetro Decagon se determinó el

porcentaje relativo de luz incidente bajo árboles. Para ello

Materiales y Métodos

se tomaron 400 mediciones en cada tratamiento bajo

árboles y 200 en sitios sin cobertura de árboles (100 antes

Periodo 2013/14

y 100 después de las mediciones bajo arboles). Las

mediciones se hicieron entre las 12:40 y las 12:52 horas,

Quince días antes del comienzo del ensayo, animales

cuando el sol se encontraba en el zenit. Los porcentajes

jóvenes Cebú cruzados alimentados previamente con caña

de radiación a cielo abierto (sin árboles) fueron 49% para

de azúcar fueron sometidos a un periodo de acostumbra-

Renopa y 48.5% para el PRT. Este nivel de luz cercano a

miento en una pastura de Axonopus catarinensis.

50% en ambos sistemas se considera suficiente para un

El área experimental consistió en 2 ha bajo árboles de

proceso fotosintético aceptable de la pastura, por lo que

Pinus taeda, la cual fue dividida en dos partes iguales y

se decidió continuar el experimento en estas condiciones.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Renopa para pastoreo rotativo 55

Periodo 2015/16

(Welham et al. 2014). Por ello los periodos de evaluación

se consideraron como repeticiones de los tratamientos de

Entre el 9 de septiembre de 2015 y el 18 de febrero de

pastoreo.

2016 se realizó un segundo ensayo de 162 días de

evaluación para comparar el PRT y el Renopa en un lote

Resultados y Discusión

diferente de A. catarinensis de 2.4 ha bajo un rodal de

P. taeda de 40 años de edad. Cada mitad del lote, 1.2 ha,

Ganancia de peso vivo

fue dividida en cinco subpotreros con una superficie

promedio de 2,400 m2 cada uno para evaluar ambos

En el periodo experimental los animales en el sistema

sistemas en forma independiente. En este caso se repitió

Renopa ganaron 35% más de peso vivo (P<0.05) que en

el protocolo empleado en el ensayo del periodo 2013/14.

el PRT (194 vs. 144 kg/ha) (Cuadro 1).

Las mediciones mostraron que la luz incidente era muy

En el Cuadro 2 se observa la probable causa de la

baja (28%) por lo que se realizó un raleo de los árboles

ganancia superior de peso vivo en el sistema Renopa, en

hasta un nivel aproximado de 50% de luz incidente. A

comparación con PRT. En el Renopa, la proporción de

diferencia del periodo 2013/14, en este segundo periodo

forraje remanente no pastado fue aproximadamente 11%,

se midieron la producción y utilización del forraje

lo que permite que el consumo voluntario y por tanto la

siguiendo el método descrito por Benvenutti et al. (2016).

ganancia diaria de peso no sean limitados antes del

cambio de potrero, como se observó en los estudios

Análisis estadístico

anteriores (Benvenutti et al. 2016; 2017). El mayor con-

sumo voluntario de los animales en el sistema Renopa es

Los resultados fueron analizados por varianza utilizando

debido al mejor acceso al estrato superior de la gramínea

el programa Genstat 2016. Este análisis fue realizado con

(= hojas con valor nutritivo más alto) por los animales. En

medidas repetidas en el tiempo utilizando las múltiples

contraste, en el sistema PRT los animales acceden al

mediciones de ganancia de peso vivo animal realizadas en

estrato inferior (= hojas y tallos de menor valor nutritivo)

cada periodo. En el contexto de este experimento que fue

resultando un remanente de 3%, lo cual produce una caída

repetido en dos periodos, la interacción entre periodo y

marcada en el consumo voluntario de forraje de menor

tratamiento es considerado como efecto aleatorio

calidad previo al cambio de subpotrero.

Cuadro 1. Peso vivo (PV) por animal y ganancia de peso por animal/día (GDP) en los sistemas Renopa y PRT en dos periodos de evaluación.

Periodo

Sistema de

PV inicial (kg)

PV final (kg)

Ganancia de

GDP (g/día)

Ganancia de

pastoreo

peso (kg/anim.)

peso (kg/ha)

2013/14 (105 días)

Renopa

194

260

66

629

198

PRT

190

238

47

451

142

2015/16 (162 días)

Renopa

184

279

95

584

189

PRT

187

250

63

389

145

Promedio

Renopa

189

270

80

606

194

PRT

189

244

55

420

144

Significancia

>0.05

<0.05

<0.05

<0.05

<0.05

Cuadro 2. Altura de pasturas después del pastoreo y remanente no pastado.

Periodo

Sistema de pastoreo

Altura después del pastoreo (cm)

Remanente no pastado (% area)

2013/14

Renopa

32.5

11.6

PRT

21.2

2.9

2015/16

Renopa

32.7

11.3

PRT

19.5

3.9

Promedio

Renopa

32.6

11.5

PRT

20.4

3.4

Significancia

<0.05

<0.05

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

56 D.R. Pavetti, M.A. Benvenutti, O. Radke y O.A. Cibils

Cuadro 3. Promedios (kg/ha) de pastura disponible y residual, y pastura utilizada para los tratamientos Renopa y PRT en el periodo 2015/16.

Sistema

Pastura disponible antes

Pastura residual

Pastura utilizada1

Pastura utilizada total2

del pastoreo

Renopa

1,650

1,008

642

8,346

PRT

1,502

893

608

7,299

1Calculada como la diferencia entre la pastura disponible menos la residual.

2Calculada como la sumatoria de la pastura utilizada para todos los cambios de potreros durante el periodo.

Cuadro 4. Determinación y comparación de los márgenes brutos1 para Renopa y PRT.

Concepto

Renopa

PRT

Periodo 2013/14

Periodo 2015/16

Periodo 2013/14

Periodo 2015/16

US$/ha

US$/anim.

US$/ha

US$/anim.

US$/ha

US$/anim.

US$/ha

US$/anim.

Ingresos brutos

1,275.51

425.17

912.37

456.18

1,167.60

389.20

943.45

408.83

Gastos por compras

1,129.02

376.34

713.88

356.94

1,105.74

368.58

837.14

362.76

Suplementación mineral

3.30

1.10

3.40

1.70

3.30

1.10

3.92

1.70

Sanidad

18.20

6.07

12.13

6,.07

18.20

6.07

14.00

6.07

Mano de obra

77.46

25.82

59.02

29.51

77.46

25.82

68.10

29.51

Margen bruto

47.53

15.84

123.94

61.97

-37.10

-12.37

20.30

8.79

1El precio de compra del ganado fue estimado en 1.94 US$/kg vivo y de venta en 1.72 US$.

Disponibilidad y utilización de forraje

Evaluación económica

Los datos en el Cuadro 3 muestran que en el sistema

El sistema Renopa generó mayor disponibilidad de

Renopa la celeridad de rebrote de la pastura fue mayor y

forraje, mayor tiempo de pastoreo, mayor carga de peso

por tanto también la producción y utilización de MS (8.34

vivo, mayor GDP y por consiguiente mejor terminación y

t/ha) que en el PRT (7.29 t/ha). Esta mayor producción es

mayor producción de carne por hectárea, lo cual resultó

probablemente debido al mayor área foliar remanente en

en mayor margen bruto que en el PRT (Cuadro 4). Se

el sistema Renopa.

puede apreciar que el sistema Renopa produjo una mayor

Cabe destacar que para lograr el nivel deseado de

eficiencia económica respecto del PRT, en ambos

remanente no pastado hay que considerar tanto la carga

periodos.

animal como el tamaño de potrero. En un potrero

pequeño, un grupo grande de animales tal vez ni deja una

Conclusión

planta no pastada el primer día de pastoreo, mientras unos

pocos animales en un potrero grande tal vez nunca

Las observaciones y resultados en este trabajo sugieren

alcanzan a comer el estrato superior en el 90‒95% del área

que el sistema Renopa, que es una estrategia simple y útil

de la pastura (para dejar un 5‒10% deseable de remanente

para definir, con base en la proporción de forraje no

no pastado).

pastado o remanente en la pastura, cuándo mover los

Además, en pasturas con gramíneas de hábito erecto o

animales en un sistema de pastoreo rotativo en

cespitoso de porte alto como Panicum maximum, el

A. catarinensis, tiene un alto potencial para maximizar la

Renopa puede dejar un nivel alto de residuos (Benvenutti

producción animal, el crecimiento de la gramínea y el

et al. 2017) con la tendencia a aumentar con cada

retorno económico del sistema.

pastoreo. Para evitar la acumulación indeseada de

residuos se pueden usar varias estrategias tales como

Agradecimientos

evitar que la pastura este muy alta al momento del

pastoreo, o utilizar un segundo rodeo de animales y/o una

Los autores agradecen a David Mayer (DAFF Agri-

máquina para consumir o cortar el residuo después del

Science Queensland, Australia) por el análisis estadístico

pastoreo del rodeo principal.

de los resultados.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Renopa para pastoreo rotativo 57

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2017. Ingestive behaviour and forage intake responses of

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Benvenutti MA; Pavetti DR; Poppi DP; Gordon IJ; Cangiano

sugarcane in pen and grazing studies. The Journal of

CA. 2016. Defoliation patterns and their implications for the

Agricultural Science 155:1677‒1688. DOI: 10.1017/

management of vegetative tropical pastures to control intake

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Welham SJ; Gezan SA; Clark SJ; Mead A. 2014. Statistical

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(Recibido para publicación 27 octubre 2017; aceptado 12 diciembre 2017; publicado 31 enero 2018)

© 2018

Tropical Grasslands-Forrajes Tropicales es una revista científica de acceso abierto publicada por el International Center for Tropical Agriculture (CIAT). Este trabajo se publica bajo la licencia Creative Commons Atribución 4.0 Internacional (CC BY 4.0). Para ver una copia de esta licencia, visite https://creativecommons.org/licenses/by/4.0/deed.es

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)