Degradability of protein fractions of conventional and non-conventional protein supplements.

Conventional [solvent extracted groundnut cake (GNC) and mechanically extracted mustard cake (MC)] and non-conventional protein supplements [mechanically extracted castor oil seed cake (COSC), un-decorticated solvent extracted neem seed cake (NSC) and corn gluten meal (CGM)] and their protein fractions were evaluated for their degradation in the rumen. Protein supplements before and after rumen incubations (for 0, 2, 4, 6, 8, 12, 24, 36 and 48 hrs) were subjected to sequential fractionation into albumin, globulin, glutelin and prolamins on the basis of solubility. The concentration of soluble proteins (albumin and globulin) was observed to be higher (P<0.05) in COSC, whereas that of insoluble protein (glutelin and prolamin) fractions was higher (P<0.05) in CGM. The globulin constituted the major (P<0.05) soluble fraction of all protein supplements selected. The 48 h crude protein degradability of groundnut and mustard cake (98 and 94%) was comparable to that of castor oil seed cake (98%), but significantly higher than that of neem seed cake (69%) and corn gluten meal (37%). The degradability of soluble protein fractions was higher (P<0.05) than that of insoluble protein fractions. Irrespective of protein supplements, the degradability of globulin was highest (P<0.05), followed by albumin, glutelin and prolamin. It was concluded that GNC and COSC were highly susceptible to rumen micro-organisms, resulting in negligible amount of rumen undegradable protein fraction, while CGM showed great resistance to rumen microbes.