Purine Nitrogen Index and Nitrogen capture efficiency as Potential parameters in evaluation of Rumen degradable nitrogen Levels for optimum microbial protein synthesis in Sheep.

Abstract

Groundnut cake (GNC) supplemented finger millet straw (FMS) based diets were evaluated for efficiency of utilization of rumen degradable nitrogen (RDN) for optimum microbial protein synthesis in sheep by the use of purine nitrogen index (PNI) and nitrogen capture efficiency (NCE), which was estimated from purine derivatives excretion in spot urine samples. Thirty six Nellore Jodipi sheep were divided into four groups of nine each. The animals in group I (GI) were fed with ad libitum finger millet straw (FMS) while those in group II, III and IV (GII,III and IV) were offered GNC to supply 13.37, 16.57, and 21.13g RDN/kg DOM along with FMS. The purine derivatives (mmol/liter) excretion and PDC index recorded were 20.05 and 26.58; 20.37 and 47.54; 23.42 and 42.04 and 23.84 and 40.95, respectively in GI, II, III and IV, respectively. The microbial purine absorption, the calculated microbial nitrogen (MN) supply (g/d) was comparable among the RDN supplemented groups (GII, III and IV). PNI and NCE values were 0.17 and 1.53; 0.23 and 0.99 and 0.15 and 0.76, respectively in GII, III and IV. The results indicated that 12.37g RDN/kg DOM or 19g RDN/kg DOMR was adequate for optimum microbial protein synthesis in sheep fed on FMS based diet. Further, the results showed that PNI and NCE estimated in spot urine of sheep fed ad libitum appeared to be useful in evaluation of RDN for Optimum microbial protein synthesis in ruminants.