Introduction

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

information on nutritive value of improved forage

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

sorghums for ranking of forage cultivars (Akabari and

important cereal crops in the semi-arid tropics globally for

Parmar 2014) and also for selecting genetic material for

providing human food, animal feed and raw materials for

use in sorghum improvement programs.

industrial use. In the present context of global climate

There is a need to quantify the genetic diversity of

change the crop is likely to become more important due to

available sorghum cultivars in terms of nutritive value for

its adaptability to high temperature, water scarcity and

use in breeding sorghum varieties or hybrids with higher

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

stover value without compromising grain yield (Rattunde

2011). Its tolerance of drought and saline conditions makes

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

sorghum a valuable feed resource for growing on saline

sorghum cultivars were screened for variability in protein,

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

carbohydrate and dry matter digestibility to select parents

India contributes 16% of global sorghum production

for subsequent use in sorghum breeding programs.

and traditionally sorghum is grown both as fodder and

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

Materials and Methods

(Maharashtra, Karnataka and Andhra Pradesh) account-

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

Production, sampling and processing of sorghum stovers

of total sorghum production. It is grown as green fodder

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

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

and later for grain as a food-feed crop.

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

Apart from producing grain as food for humans plus

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

non-ruminant and ruminant livestock, sorghum residue

308), selected on the basis of diverse genetic

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

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

nants in the tropics, including India. The nutritive value

were grown at the research farm of Indian Institute of

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

Millet Research, Hyderabad, India, in a randomized block

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

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

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

cm between rows and 15 cm between plants within rows.

tance of crop residues for livestock feed, improving the

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

nutritive value of sorghum stover is an important object-

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

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

in number of days to grain ripening since planting varied

Reddy (2006) reported substantial variation in the fodder

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

value of sorghum stovers and supported the concept of

700 matured in 122 days with the remainder intermediate.

genetic enhancement to improve dual-purpose sorghum

Yields of grain and stover were measured following grain

cultivars. Genetic variability in sorghum for various nutri-

harvesting and a composite stover sample was taken from

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

each replication of individual cultivars for chemical

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

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

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

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

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

ADIP, samples extracted with neutral detergent and acid

were then ground through a 1-mm sieve using an

detergent solutions, respectively, were analyzed as

electrically operated Willey mill and subsequently stored

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

in plastic containers for laboratory analysis.

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

were treated with sodium tungstate (0.30 molar) and

Chemical analyses

filtered, and residual nitrogen was determined by the

Kjeldahl procedure. Non-protein nitrogen of the sample

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

was calculated by subtracting residual nitrogen from total

and ash concentrations of sorghum stover samples were

nitrogen. Soluble protein (SP) was estimated by treating

estimated as per procedures of AOAC (2000). Fiber

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

fractions, namely neutral detergent fiber (NDF), acid

consisting of monosodium phosphate (Na2PO4.H2O) 12.2

detergent fiber (ADF), cellulose and lignin, were

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

determined following the detergent method of Van Soest et

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

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

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

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

N estimated in the residue gives the insoluble protein

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

fraction. The SP was calculated by subtracting insoluble

was determined by dissolving cellulose with sulfuric acid

protein from total CP.

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

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

Intake, digestibility, energy, feed value

the sequential analysis and hemicellulose was calculated as

difference between NDF and ADF concentrations.

To calculate DM intake (DMI), digestible dry matter

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

Carbohydrate and protein fractions

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

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

Total carbohydrates (tCHO) of stover samples were

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

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

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

fractions in the samples were estimated as per Cornell Net

(NE) values were calculated using equations of Fonnesbeck

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

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

1992), which classifies carbohydrate fractions according

vitro dry matter digestibility (IVDMD) was estimated using

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

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

degradable sugars; CB1 - intermediately degradable starch

incubating 0.5 g of sample in inoculum of sheep maintained

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

on a mixed grass hay-concentrate diet.

unavailable/lignin-bound cell wall. Structural carbo-

hydrates (SC) were calculated as the difference between

Minerals

NDF and neutral detergent insoluble protein (NDIP),

while non-structural carbohydrates (NSC) were estimated

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

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

HNO3:perchloric acid mixture, cooled and filtered

2001). Starch in samples was estimated by extracting

through Whatman 42 filter paper. The aliquot was used

stover samples in 80% ethyl alcohol to solubilize free

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

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

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

starch was solubilized with perchloric acid and the extract

atomic absorption spectrophotometer (Varian AA 240)

was treated with anthrone-sulfuric acid to determine

against their standards. Phosphorus was estimated colori-

glucose colorimetrically using glucose standard (Sastry et

metrically using Bartor’s reagent according to AOAC

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

(2000).

starch (mg %).

The CP of stover samples was partitioned into 5

Statistical analysis

fractions according to the Cornell Net Carbohydrate and

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

Data were subjected to analysis of variance of SPSS 17.0

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

to test the differences between sorghum cultivars for

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

chemical composition, carbohydrate and protein fractions,

and non-protein nitrogen (NPN) were estimated following

energy values, digestibility and mineral concentrations.

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

Nutritional attributes in stover of sorghum cultivars 45

Variable means were compared for significance at P<0.05

Carbohydrate fractions

level (Snedecor and Cochran 1994).

Concentrations of tCHO, NSC and SC of sorghum stovers

Results

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

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

Grain and stover yields

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

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

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

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

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

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

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

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

(SPV-1616) (Table 1).

degradable carbohydrate fraction (C

A) was highest

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

Chemical composition

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

All chemical parameters varied (P<0.05) between

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

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

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

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

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

Protein fractions

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

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

The protein fractions PB1, PB2, PB3 and PC differed

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

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

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

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

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

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

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

lowest in ICSV-700 (20.4% CP).

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

Cultivar

Commodity/Major utility

Stover yield (t/ha)

Grain yield (t/ha)

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

Sweet sorghum/ High biomass

13.7a

2.82cd

PC-5

Fodder

8.96bc

2.23de

GGUB44 x SSG-59-3

Fodder

10.05abc

2.18d

ICSV-700

Sweet sorghum/ High biomass

12.51ab

2.7c

CSV-17

Grain & fodder

7.61c

3.4c

NRF-526

Sweet sorghum/ High biomass

12.07ab

2.46d

FM-1

Fodder

9.49abc

1.59e

SPV-1616

Grain & fodder

11.34abc

4.51a

PVK-809

Grain & fodder

10.76abc

3.89ab

UMPC-503

Fodder

8.6c

2.03de

HC-308

Fodder

9.95abc

1.79e

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

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

Variable

SP 18005A

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

Sig

x 220-2,3,6,7

SSG-59-3

CP

6.6ef

6.71f

5.87de

4.88bc 4.53abc 4.43abc 5.03c

3.87ab

4.46abc

3.68a

4.07ab 0.134 <0.0001

OM

91.5abc

93.1de

93.0de

93.2de 92.6cde 91.9abcd 93.3de

91.1a

91.0a

93.5e

92.4bcde 0.159 <0.0001

EE

1.21ab

1.14ab

1.24ab

1.05a

1.28abc 1.61d

1.51d

1.25ab

1.29cd

1.14ab

1.22ab 0.026 <0.0001

NDF

63.0b

64.0b

62.3b

55.0a

68.2c

62.1b

61.5b

61.7b

62.0b

63.9b

64.1b 0.474 <0.0001

ADF

38.1ab

38.7b

36.8ab

35.3a

43.1c

38.9b

36.2ab

37.0ab

38.0ab

37.7ab

39.0b 0.335 <0.0001

Cellulose

30.3b

31.7b

29.9ab

27.9a

33.8c

30.7b

29.4ab

30.2b

30.8b

31.5b

31.1b 0.251 <0.0001

Hemicellulose

25.5bc

25.6bc

25.5bc

19.7a

25.2bc

23.3b

25.4bc

24.7bc

23.9bc

26.2c

25.1bc 0.286 <0.0001

Lignin

5.51ef

4.84abc

4.48ab

4.96bcde 5.79f

5.58ef 4.73abc 4.54ab

4.33a

4.64abc

5.04bcd 0.074 <0.0001

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

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

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

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

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

Variable

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

220-2,3,6,7

SSG-59-3

tCHO (% DM)

83.3a

84.9ab

85.1ab

86.8cd

86.3bc

85.3ab

86.6cd 85.8abc

84.6abc

88.6d

87.0cd 0.306 0.007

NSC (% DM)

22.7a

23.1a

24.4a

33.2b

19.9a

24.8a

27.6ab

26.1ab

25.7ab

26.5ab

24.8a 0.760 0.102

SC (% DM)

60.7b

61.8bc

60.7b

53.6a

66.4c

60.5b

59.0b

59.7b

58.9b

62.1bc

62.2bc 0.631 0.012

CA (% tCHO)

20.2ab

20.2ab

22.7ab

30.3c

16.7a

21.6ab

24.5bc

20.9ab

21.9ab

21.7ab

20. 9ab 0.744 0.002

CB1 (% tCHO)

0.95a

2.26bc

1.60abc

1.50abc 1.41ab

1.38ab

2.20bc

4.30d

3.57d

3.64d

2.55c 0.188 0.028

CB2 (% tCHO)

62.8b

64.5b

64.0b

53.8a

66.4b

61.1b

59.9b

61.4b

62.2b

61.9b

62.5b 0.680 0.0001

CC (% tCHO)

16.0d

13.0ab

11.7a

14.4bcd 15.5cd

15.9d

13.3abc 13.3ab

12.3ab

12.7ab

14.2bcd 03.05 0.063

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

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

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

Energy and its efficiency for animal functions

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

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

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

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

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

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

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

CSV-17 (40.3%).

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

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

Macro- and micro-minerals

DM and 48.9%, respectively). The energetic efficiency

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

Macro- and micro-mineral concentrations in stovers

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

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

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

Stover from SPV-1616 had lowest Ca and P

DM, respectively.

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

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

Intake, digestibility and relative feed value

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

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

The calculated values of DMI, DDM and RFV for stovers

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

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

and 5.44 ug/g, respectively.

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

Variable

SP 18005A x

PC-5

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

SPV-

PVK- UPMC-503 HC-308 sem

Sig

220-2,3,6,7

SSG-59-3

1616

809

PA

8.95

9.28

6.66

7.73

8.55

6.44

8.49

6.94

11.51

10.29

9.15

0.48 0.661

PB1

26.7ab

26.1ab

21.8a

25.1ab

26.2ab

26.6ab

25.3ab

25.4ab

22.9a

30.0bc

34.1c

0.66 0.010

PB2

33.1bc

30.2abc

36.6c

28.8abc 28.5abc

33.7c

21.4ab 25.0abc

20.9a

21.5ab

20.8a

1.23 0.040

PB3

4.99a

12.93abc 11.30abc

17.96c 12.30abc 12.17abc 16.58bc

5.79a

11.03ab

9.67ab

7.82a

0.854 0.016

PC

26.3ab

21.5a

23.6a

20.4a

24.4a

21.1a

28.3ab

36.8c

33.6bc

28.6ab

28.5ab 0.999 0.002

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

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

indigestible protein.

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

Nutritional attributes in stover of sorghum cultivars 47

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

Variable

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

Sig

220-2,3,6,7

SSG-59-3

GE (kcal/g)

4.17bc

4.01a

4.11abc

4.04ab 4.12abc 4.14abc

4.22c

4.16abc

4.04ab

4.13abc 4.13abc 0.014 0.118

DE (kcal/g)

2.44bc

2.41b

2.52bc

2.60c

2.16a

2.40b

2.55bc

2.50bc

2.44bc

2.46bc

2.39b 0.019 <.0001

ME (kcal/g)

2.00bc

1.90b

2.07bc

2.13c

1.77a

1.97b

2.10bc

2.06bc

2.01bc

2.02bc

1.96b 0.016 <.0001

TDN (%)

55.3bc

54.6b

57.1bc

59.0c

48.9a

54.4b

57.9bc

56.8bc

55.4bc

55.9bc

54.2b 0.437 <.0001

NEL (kcal/g)

1.19bc

1.16b

1.26bc

1.33c

0.95a

1.15b

1.29bc

1.24bc

1.19bc

1.21bc

1.15b 0.016 <.0001

NEG (kcal/g)

0.59bc

0.57b

0.65bc

0.70c

0.41a

0.57b

0.67bc

0.64bc

0.60bc

0.61bc

0.56b 0.013 <.0001

NEM (kcal/g)

1.31bc

1.29b

1.37bc

1.42c

1.13a

1.29b

1.39bc

1.36bc

1.32bc

1.33bc

1.28b 0.0126 <.0001

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

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

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

Variable

SP 18005A x

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

sig

220-2,3,6,7

SSG-59-3

IVDMD (%)

51.1cde

47.6bc

52.6def

54.3ef

40.3a

47.7bc

53.7ef

50.9cde

55.7f

48.4bcd

45.7b 0.552 <.0001

DDM (%)

59.2bc

58.7b

60.2bc

61.4bc

55.3a

58.6b

60.7bc

60.1bc

59.3bc

59.5bc

58.5b 0.261 <.0001

DMI (%)

1.89b

1.86ab

1.93b

2.19c

1.76a

1.94b

1.95b

1.95b

1.94b

1.88b

1.87ab 0.015 <.0001

RFV (%)

86.7b

85.1b

90.1b

104.1c

75.4a

88.2b

92.0b

90.9b

89.7b

87.0b

85.0b 1.038 <.0001

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

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

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

Variable

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

Sig

220-2,3,6,7

SSG-59-3

Ca (mg/kg)

343c

236bc

259ab

241ab

341ab

398cd

228bc

216a

215a

241ab

285abc 10.01

0.001

P (mg/kg)

45.9abc

42.3ab

62.6abc

56.4abc 47.9abc 47.2abc 60.7abc 39.9ab

42ab

65.6bc

71c

2.60

0.071

Mg (mg/kg)

58.6

49.8

44.5

46.0

42.9

54.5

52.1

44.9

45.0

42.9

48.6

2.40

0.013

Cu (ug/g)

4.45b

1.86a

1.55a

1.54a

5.45b

8.51c

8.25c

1.47a

2.94a

3.71a

9.59c

1.76

0.032

Zn (ug/g)

14.9

17.2

16.4

27.3

32.2

18.2

14.2

24.5

28.6

35.5

23.8

0.623

0.410

Fe (ug/g)

230ab

277b

281b

195ab

241ab

272b

173ab

149a

164ab

109a

126a

20.17

0.001

Mn (ug/g)

98.3cd

69.2abc

112.5d

68.3abc 54.6ab 71.3abc 54.7ab 74.3abc

83.4bcd

65.0abc

46.5a

3.94

0.011

Co (ug/g)

3.86abc

3.06abc

4.30bc

3.50abc 3.04abc 4.85bc

1.74a

3.05abc

2.57ab

4.25bc

5.44c 0.258

0.026

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

Discussion

fodder yields and biomass, and hence better suited as a

dual purpose sorghum variety. Sharma (2013) observed

Grain and stover yields

that CSV 17 was a good grain yielding variety that had

least stover yield in western Rajasthan, India.

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

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

Chemical composition

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

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

Cereal stovers and straws are usually low in crude protein

biomass lines were specially bred for higher biomass. On

and rich in fiber concentrations, unable even to meet the

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

minimum CP requirements (7%) for maintenance of

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

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

varieties were bred for maximizing grain yield with

need to supplement these stovers with protein rich

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

leguminous forage or non-protein nitrogen or protein

that SPV 1616 showed high adaptability for grain and

sources. In the present study CP concentrations (3.7‒

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

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

6.7%) of sorghum stovers are below the maintenance

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

requirement for ruminants. Mativavarira et al. (2013)

tration influences carbohydrate fraction CB2 and forages

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

high in NDF concentration usually have higher values of

across cultivars and ranged between 5.6 and 6.6%, which

CB2. Values of carbohydrate fraction CC in our study

supports our findings. Varietal differences for sorghum

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

stover quality have been reported for protein and cell wall

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

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

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

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

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

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

attributed to differences in concentrations of CP and

across 5 sorghum varieties. Crude protein, OM and EE

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

concentrations of sorghum stovers reported by Misra et

or rather, is unavailable to ruminal microorganisms (Van

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

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

and ADF concentrations were higher than our values.

study ranged between 20.4 and 36.8% CP, exceeding the

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

above levels, probably due to variability in lignin

and lignin concentrations of sorghum stovers in different

concentrations. Forages, fermented grains and byproduct

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

feeds contain significant amounts of fraction PB3

Hamed et al. 2015).

(Krishnamoorthy et al. 1983).

Carbohydrate and protein fractions

Energy and its efficiency

Carbohydrates constitute the main energy source of plants

Energy density of roughages is a primary parameter

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

influencing animal productivity. Stovers from the

as a prime source of energy for rumen microorganisms

evaluated sorghum cultivars had adequate energy, except

(Van Soest 1994). In our study total carbohydrate

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

concentrations of sorghum stovers varied between 83.4

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

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

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

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

concentrations in our study differed (P<0.05) across

crops is influenced by several factors like plant species,

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

variety, growth stage and environmental conditions

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

during growth (Buxton and Fales 1994). Concentrations

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

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

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

suggested by Ferraris and Charles-Edwards (1986) and

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

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

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

evaluating the nutritive value of crop residues, found that

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

CA, CB1, CB2 and Cc concentrations in sorghum stover

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

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

variation in TDN concentrations in our study (59.0% for

of carbohydrate fractions identical with our results. Rela-

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

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

differences in fiber concentrations, as fiber is often used

may be due to the lower lignin concentrations in our

as a negative index of nutritive value in the prediction of

stovers than in theirs. In our results carbohydrate fraction

total digestible nutrients and net energy. Sorghum stover

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

TDN concentrations of 46.5‒56.5% reported by Garg et

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

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

higher NDF and hemicellulose concentrations in CSV-17

Beef Magazine (2015) suggests TDN concentrations of

and lower NDF and hemicellulose concentrations in

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

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

reported TDN of silage made from sorghum hybrids

with high NDF levels had higher concentrations of the CB2

between 54.4 and 62.2%. Studies on the net energy

fraction, which is more slowly degraded in the rumen,

efficiency of sorghum stovers for animal production

impacting microbial synthesis and animal performance

functions is limited and values for NEM, NEG and NEL

(Ribeiro et al. 2001). Higher hemicellulose concentrations

reported in Beef Magazine (2015) for sorghum stover of

result in higher concentrations of carbohydrate CB2

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

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

Nutritional attributes in stover of sorghum cultivars 49

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

Macro- and micro-minerals

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

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

Forages neither contain all the required minerals nor are

within the range of energy values for sorghum stovers

they present in adequate quantity to meet animal

recorded in our study.

requirements (Vargas and McDowell 1997). Calcium and

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

Intake, digestibility and relative feed value

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

almost all tissues in the body and must be available to

From a livestock production view point, intake and

livestock in proper quantities and ratio (McDowell et al.

digestibility are the main criteria in breeding programs for

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

quality improvement in most cereal fodder crops. Dietary

mg/kg, should fulfill the maintenance requirements of

ruminants (270‒570 mg/kg;

fiber concentration, its digestibility and rate of degradation

NRC 2001), but P and Mg

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

in the rumen are the most important forage characteristics

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

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

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

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

the Ca concentrations in sorghum stover/straws reported

attributed to differences in NDF concentrations. The NDF

by Ramesh et al. (2014) and Garg et al. (2003) are more concentration of CSV-17 was 68.2%, which exceeds the

or less similar to our values, P concentrations reported by

60.0% usually considered as the threshold likely to

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

significantly reduce intake in ruminants (Zewdu 2005).

(2015) reported P and Mg concentrations in sorghum

Mahanta and Pachauri (2005) recorded DMI between 1.84

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

and 2.55% for sheep fed silage from 3 sorghum cultivars

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

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

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

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

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

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

(2015). The low concentrations of many minerals in

attribute the lower RFV of stovers in the present study to

straws and stovers are probably due to maturity and

their lower quality relative to the whole plants examined at

possible transfer of nutrients to seeds. Mineral

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

concentrations in feeds and fodders are influenced by a

ADF concentrations as these influence the intake and

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

digestibility of a fodder. Forage containing 41% ADF and

of growth and harvest, crop yield, intensity of agriculture

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

system, climate, fertilizer rate etc. (British Geological

values decrease as the concentrations of NDF and ADF

Survey 1992; McDowell et al. 1993).

increase with crop maturity.

The results from this study revealed significant

The variability in digestibility values may be attributed

variability in apparent nutritive value of the sorghum

to differences in cell wall concentrations. Elseed et al.

stovers tested. This indicates that there is considerable

(2007) reported effective degradability of dry matter of

potential for selecting appropriate genotypes to include in

stovers from different cultivars between 44.4 and 67.7%,

breeding programs to improve stover quality. While

which covers a similar range to our IVDMD and DDM

stovers of all genotypes had adequate energy to meet

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

ruminant maintenance requirements, protein concen-

between forage fiber fractions and DM digestibility, while

trations were low and quite variable. While there is

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

potential to improve stover quality by breeding, care

indicated that nitrogen concentration and cell wall poly-

would need to be taken to ensure grain and stover yields

saccharides determine the digestibility of a crop. The

did not suffer as a result. Feeding studies with animals

IVDMD of sorghum stover of 53.3% reported by Misra et

would throw more light on the predicted feed intakes and

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

digestible dry matter values reported in this study.

The lower concentrations of NDF, cellulose and lignin in

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

Acknowledgments

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

Thomas 2003), while the highest lignin concentration

Authors are thankful to Department of Biotechnology for

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

providing financial assistance to carry out this research

explain the lowest IVDMD and DDM values for this

work. Thanks to Director, Millet Research Institute,

cultivar.

Hyderabad and Director, Indian Grassland and Fodder

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

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

Research Institute, Jhansi for providing facilities for

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

conducting this work.

carbohydrate and protein content of some forage feeds of

ruminants for nutritive evaluation. Veterinary World 8:197–

202. DOI: 10.14202/vetworld.2015.197-202

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(Received for publication 05 December 2016; accepted 28 September 2017; published 31 January 2018)

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