Microbial Protein Yield in Sheep Fed Forage Legume Hays as Supplements to Veld Hay

This study examined the effects of feeding forage legumes as protein supplements to poor quality natural pasture (veld) hay offered to sheep on microbial protein yield and nitrogen metabolism. Four female Sabi cross-bred sheep were used in a 4 x 4 Latin cross-over design experiment. The sheep were randomly allocated to four dietary treatments comprising veld hay alone (V), veld hay supplemented at 25% of expected feed intake with either cowpea (VC), fine stem stylo (VF) or silverleaf desmodium (VS). Microbial protein yield was determined using the purine derivatives technique. Total nitrogen (N) intake increased with supplementation by approximately 9, 11 and 17 fold for VS, VF and VC, respectively. The microbial protein supply, the calculated microbial true protein and the digestible microbial true protein were not affected (P>0.05) by legume supplementation. It was concluded that supplementation of legume forages to poor quality veld hay increased nitrogen utilisation in the sheep. Animals on poor quality forages tended to show the most efficient microbial protein synthesis. However, feeding of veld hay failed to meet the maintenance requirements of the animal as evidenced by negative nitrogen balance.