Cowpea ( Vigna unguiculata) legume grains as protein source in the ration of growing sheep

Abstract

A growth trial of 120 days was conducted on 15 growing sheep to evaluate cowpea grains as an alternate protein source of groundnut cake (GNC). Animals were divided in three groups of five animals in each, and offered dry mixed grasses ( Cenchrus ciliaris, Sehima nervosum with small proportion of Chryosopogon fulvus and Dicanthium annulatum) and concentrate mixtures to meet their nutrient requirement. In the concentrate mixture of G1 (control group), GNC was the sole source of protein, while in the G2 and G3 groups, 50 and 100% of GNC was replaced by cowpea grains on N basis. After 75 days of feeding, a metabolism trial (7 days) was conducted to determine the dry matter intake (DMI), nutrients utilization and N-balance. Rumen liquor and blood samples were collected to estimate the rumen and blood metabolites, respectively. For eating pattern, observations were recorded for three consecutive days. Change in body weight of animals was recorded at 15 days interval. CP and cell wall polysaccharide contents were higher in GNC than in cowpea grain. DMI (g kg −1 W 0.75) was higher ( P < 0.05) in G2 and G3 (85.8 ± 3.23 and 88.6 ± 1.40) compared to G1 (80.0 ± 2.44). In total DMI, consumption of roughage was higher ( P < 0.05) in G3 than G1 and G2. Digestibility of nutrients (CP and fiber fractions) was similar amongst the dietary groups, except EE digestibility that varied ( P < 0.05) amongst the groups. Nitrogen-intake (g day −1) was ( P > 0.05) higher in G3 (17.4 ± 1.21) than G2 (15.7 ± 0.80) and G1 (14.0 ± 0.60). Absorbed nitrogen (g day −1) was ( P < 0.05) higher in G3 (5.1 ± 0.46) compared with G2 (4.0 ± 0.28) and G1 (3.6 ± 0.15). Percent DCP and TDN tended to be higher in G3 compared to other dietary groups. DE (K cal g DM −1) of diets in G3 (2.8 ± 0.77) was higher than G1 (2.2 ± 0.05) and G2 (2.5 ± 0.09) groups. TVFA and NH 3–N concentrations were 143.2 ± 17.94, 137.5 ± 14.38 and 140.7 ± 9.97 meq/l and 18.2 ± 0.59, 19.6 ± 2.21 and 20.65 ± 1.52 mg/100 ml in G1, G2 and G3 groups, respectively. Total-N concentrations was significantly ( P < 0.05) higher in G3 (112.0 ± 12.51) compared to G2 (91.84 ± 15.59) and G1 (94.71 ± 4.26 mg/100 ml) groups. Blood metabolites were comparable amongst the dietary groups. Concentrate consumption (g/30 min) was ( P < 0.05) higher in G3 (469.0 ± 11.83) and G2 (422.5 ± 50.76) than G1 (277.0 ± 26.25). However, the meal size (g h −1 and g kg −1 W 0.75 h −1) during first 4 h of eating was comparable between the dietary groups. Average body weight gain (g day −1) was ( P < 0.05) higher in G3 (58.8 ± 3.02) than G1 (46.0 ± 1.65). Results deduced that inclusion of cowpea grains in concentrate mixture of lambs had positive effect on roughage intake, nitrogen-balance, nutritive value and body growth besides the rumen metabolites.