Effective protein degradability and changes in amino acid spectrum after incubation of grains and mill feeds in rumen

An in sacco method was used in three bulls to determine effective protein degradability and amino acid decrease after incubation of barley, corn, oats, wheat, wheat feeding meal, wheat and rye bran in the rumen. Dietary amino acid N content ranged from 12.6 to 21.9 g/kg dry matter; it was 60.8-87.6% of the total N content. The highest proportion of nonessential amino acids in grains was determined in Glu, of essential amino acids in Leu, and also in Lys in wheat bran. Except corn, effective degradability of proteins in other feeds was high at k = 0.06, amounting to about 80%. Differences between the types of feeds were significant (P < 0.01). Degradation rate of protein ranged from 0.064 per hour for corn to 0.176 per hour for rye bran. Similar decreases in proteins and total amino acids were determined in feed residues after 16-hour incubation. There were differences between the amino acids and between the feeds. Decreases in corn amino acids were from 47 to 80.6% while decreases in all amino acids in other feeds were higher than 80%, up to 96.9% in rye bran Gill. Following the incubation, the amino acid spectrum showed great changes in comparison with that of original feed. His and Glu proportions in grains largely decreased, the same applies to Arg and Pro in bran. Lys proportion increased except in barley and corn. Small changes were observed in the proportions of amino acids with branched chain and Met.