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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