Protein evaluation in ruminants in vitro, in sacco, in vivo protein degradability and microbial efficiency of different protein supplements in growing buffalo calves

Abstract

The most common protein supplements, i.e. groundnut cake (GNC), mustard cake (MC), cottonseed cake (CSC), guar meal (GM), poultry excreta (PE), jowar gluten meal (JGM), maize gluten meal (MGM), brewer's grain waste (BGW) and single cell protein (SCP) were evaluated for their in vitro, in sacco and effective protein degradability (EPD) estimates. The in vivo rumen protein degradability of GNC, MC, CSC, GM and PE were measured in growing buffalo calves fitted with T-type duodenum cannulae. The in vitro, in sacco and EPD estimates of ruminal protein degradability in buffalo calves were respectively 81.9%, 96.3% and 77.9% for GNC; 78.3%, 92.6% and 64.2% for MC; 61.4%, 81.4% and 52.4% for CSC; 83.0%, 97.3% and 75.1% for GM; 54.1%, 78.8% and 55.3% for PE; 21.0%, 59.2% and 33.2% for JGM; 24.6%, 60.9% and 31.3% for MGM; 34.0%, 77.7% and 43.9% for BGW; 68.0%, 97.6% and 68.9% for SCP. The in vivo estimates of the ruminal degradation of supplemental proteins obtained were: GNC, 76.4%; MC, 70.3%; CSC, 60.5%; GM, 89.8%; PE, 55.2%. The highest microbial efficiency (g N kg −1 organic matter digested in the rumen (OMD R)) was obtained with a ration based on PE (34.4) followed by GM (32.9), MC (28.9), CSC (24.0) and the lowest on GNC (18.3). The in vitro degradation of protein supplements, i.e. GNC, MC, CSC, GM and PE at 48 h was in close agreement with the in vivo degradation, the difference being nonsignificant. It may be concluded that to screen newly available agro-industrial by-products for protein degradability, the in vitro technique can be adopted, but for reliable estimates of protein degradability and microbial efficiency of protein supplements, the in vivo (duodenum cannulated) measurements should be obtained.