Nitrogen Fractions, Digestion Kinetics and In Vitro Digestibility of some Ruminant Feeds

N fractions, digestion kinetics, in vitro nutrients digestibility, ammonia nitrogen and gas production of some common oil cakes (mustard cake, groundnut cake, formaldehyde (FA) treated mustard and groundnut cake), grains (maize, wheat and barley), wheat bran, maize fodder and wheat straw were determined. Phosphate buffer soluble N (A+B1fraction) was highest in mustard cake, groundnut cake followed by wheat bran, barley and maize fodder whereas fibre bound N (C fraction) was highest in wheat straw followed by maize fodder. Highest effective protein degradability (EPD) was in in mustard cake, wheat bran and groundnut cake while lowest in FA treated mustard cake and groundnut cake. Maize fodder and wheat straw had effective degradability (kp= 0.02% per h) of 76.40 and 59.10%, respectively. Production of ammonia N was highest in groundnut cake and lowest in wheat straw. In vitro DM digestibility and gas production were highest in mustard cake and lowest in FA treated groundnut cake. Correlation coefficient (r) between EPD with A+B1, B2, B3 and C were 0.94, -0.63, 0.12 and -0.36, respectively. Regression equations for EPD from different protein fractions individually or in combination were significant (P<0.01). Regression equations for IVDMD, gas production or ruminal ammonia N concentration from all 4 fractions of protein were also significant (P<0.05). It was concluded that estimation of N fractions is one of the good methods for prediction of rumen protein degradability.