In-vitro methane production potential and in-sacco degradability of conventional and non-conventional protein supplements

Abstract

The study was taken up to assess the in-vitro methane and total volatile fatty acids (TVFAs) production; in sacco degradability and metabolizable energy (ME) availability from conventional and non conventional protein supplements like mustard cake (MC), deoiled mustard cake (DMC), deoiled groundnut cake (DGNC), soybean meal (SBM), cottonseed cake (CSC), corn gluten meal (CGM), maize oil cake (MOC), tomato pomace (TP) and spent brewers grains (SBG). The CP content varied from 18.2 (TP) to 66% (CGM). TP had the highest EE (11.0%) and lignin (13.5%) content. The net gas production (NGP) varied significantly from 80.7 ml/g DM (CSC) to 236.8 ml/g DM (MOC). The in-vitro methane production (expressed as ml/g DM) was the lowest from CSC and CGM, while the highest was observed from SBM and MOC. But when methane was expressed as per cent of NGP or as ml/g digestible OM at t1/2, the significantly lowest methane production was observed from TP followed by that from CSC, SBG MC and CGM. The protein supplement with high rumen undegradable protein (RUDP) content produced less methane as compared to the ones that had low UDP content. The TVFA production was the lowest from CSC, which may be due to the lowest degradability of OM and NDF. The digestion kinetic parameters for DM and CP revealed that the rate of degradation was significantly lowest in CGM and highest in DGNC (DM) and TP (CP). The effective degradability (ED) was lowest in CGM and highest was observed in SBM (DM) and DGNC (CP). The rumen UDP as per cent of total protein in CGM was significantly higher than all other protein supplements, it was followed by TP and was lowest in DGNC. It was concluded that the protein supplements with high rumen RUDP value like tomato pomace, cotton seed cake, spent brewer’s grains and corn gluten meal had low methane production potential.