The evaluation of metabolizable protein content of some indigenous feedstuffs used in ruminant nutrition

Aim: To determine the metabolizable protein (MP) content of common indigenous feedstuffs used in ruminant nutrition using in situ method. Materials and Methods: Nine ruminant feeds such as maize grain (MG), groundnut cake (GNC), mustard oilcake (MOC), cottonseed cake (CSC), deoiled rice bran (DORB), wheat bran (WB), berseem fodder (BF), maize fodder (MF) and sorghum fodder (SF) were included in this study. Each test feed was dried, ground and chemically analysed for proximate principles (DM, CP, EE, OM, Total ash), fiber fractions (NDF, ADF, cellulose, hemicellulose, lignin), NDICP and ADICP. Two adult fistulated bulls were used for evaluating the protein degradation characteristics of each test feed using the nylon bag method. Metabolizable energy (ME) content of the test feeds were predicted from their chemical composition data using summative approach of NRC (2001) model. The equations of AFRC (1992) were used to predict the rumen degradable protein (RDP), digestible microbial protein (DMP), digestible undegraded feed protein (DUP) and MP content of test feeds. Results: The MP content of MG, GNC, MOC, CSC, DORB, WB, BF, MF and SF was found to be 95.26, 156.41, 135.21, 125.06, 101.68, 107.11, 136.81, 72.01 and 76.65 g/kg DM, respectively. The corresponding ME (MJ/kg DM) content of the test feeds was 13.66, 13.12, 13.65, 10.68, 9.08, 11.56, 9.64, 8.33 and 8.03, respectively. Among the test feeds, GNC contained the highest and MF contained the lowest MP per kg DM. Conclusion: It was concluded that the degradability of crude protein (CP) of the test feeds can be used in MP determination and diet formulation. Feed CP content is not available as such at intestinal level in ruminants as a definite part of it undergoes extensive microbial degradation in rumen. The pattern and extent of such degradation do influence the amount of protein presented to lower digestive tract (MP) for absorption and utilization in ruminants. It was also found that the MP content of a feed is not constant as that of its CP content as it entirely depends on the degradation characteristics in a given animal.