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
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
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
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.
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
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
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.
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Epasinghe TM; Jayawardena VP; Premalal GGC. 2012.
Our findings suggest that both Sugar Graze and Jumbo
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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
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
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
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
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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(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