Nutritive value of cowpea fodder cultivars and their effect on nutrients intake, digestibility and nitrogen balance in sheep

Abstract

Three cowpea fodder varieties (BL-1, BL-2 and BL-4) developed by IGFRI were evaluated against check Kohinoor for their nutritional attributes by in vitro and in vivo means. Varieties were grown under identical agronomic practices in Kharif 2016 and animal feeding was started at flower initiation stage. For feeding trial, 20 growing sheep (mean body weight 19.85±0.45 kg) were randomly distributed to 4 varieties (Kohinoor, BL-1, BL-2 and BL-4) with 5 animals to each. After 3 weeks of feeding, a digestion cum- metabolism trial was conducted to assess the nutrients intake, digestibility and nitrogen balance in sheep. The cowpea fodder varieties CP, NDF and lignin contents differed and values ranged between 22.23–23.41, 50.54–55.10 and 8.48–10.76%, respectively. Protein and carbohydrate fractions of cowpea varieties were similar except the NSC (% DM) and CC (% CHO) which were lower and higher, respectively in BL-2. Cowpea varieties energy values as TDN, DE, NEL, NEM and NEG were identical. In vitro gas and methane production (ml/g DM) was lower from Kohinoor (86.57 and 10.67) and BL-2 (90.79 and 11.40) than BL-1 (104.83 and 13.96) and BL-4 (98.86 and 13.08), respectively. Short chain fatty acids, partition factor and efficiency for microbial production differed significantly amongst the cowpea varieties. Sheep DM, CP and ME intake (% body wt and g/kg W0.75) was comparable on evaluated cowpea varieties. Digestibility of DM, OM and CP in sheep was similar on cowpea varieties; however, NDF and ADF digestibility tended to be lower of BL-4 (63.88 and 61.70%) than BL-2. Sheep nitrogen balance was identical on all the cowpea varieties and ranged between 16.92–18.32 g/d. Cowpea varieties DCP and DE contents were similar and ranged between 18.36–20.30% and 13.63–14.72 kjoules/g DM, respectively. Results showed that nutritive value of cowpea varieties differed significantly in terms of CP, NDF, NSC%DM, fermentation pattern, and cell wall (NDF and ADF) digestibility.