Microbial protein synthesis, nitrogen capture efficiency and nutrient utilisation in sheep fed on finger millet straw (Eleucine coracana)-based diet with different rumen-degradable nitrogen levels

Abstract

Microbial protein synthesised in the rumen is a very important protein source for ruminants. It is essential to provide an adequate amount of rumen-degradable nitrogen (RDN) for optimum microbial protein synthesis in the rumen on straw-based diets. The objective of this study was to determine the RDN requirement for optimum microbial protein synthesis (MPS), nitrogen capture efficiency (NCE) and nutrient utilisation in Nellore rams fed on a finger millet straw (FMS)-based diet. Thirty-six Nellore sheep were randomly divided into four groups of nine animals each using a balanced, completely randomised design. The animals in group 1 (RDN0) were fed with ad libitum FMS. Those in groups 2, 3 and 4 (RDN1, RDN2 and RDN3) were supplemented with groundnut cake to provide RDN levels of 14, 18 and 23 g RDN kg⁻¹ digestible organic matter intake (DOMI) or 21, 27 and 35 g RDN kg⁻¹ digestible organic matter apparently digested in the rumen (DOMR) respectively along with FMS. The digestibility coefficients of all nutrients and MPS increased (P < 0.05) quadratically with increasing level of RDN supplementation. NCE decreased linearly (P < 0.05) as the level of RDN increased. The results suggest that 12 g RDN kg⁻¹ DOMI or 19 g RDN kg⁻¹ DOMR may be adequate for optimum MPS, NCE and digestibility of nutrients in sheep fed on an FMS-based diet.