Rumen degradability of concentrate protein, amino acids and starch, and their digestibility in the small intestine of cows

Abstract

The in situ and mobile nylon bag methods were used to determine the effective degradability of dry matter, crude protein and starch in the rumen and the digestibility of undegraded protein and individual amino acids of various feeds in the small intestine of the cow. The tested feeds included rapeseed oilmeal obtained from six industrial oil mills, soyabean oilmeal, field peas (coloured flowered), peas, field beans, lupin, rye, triticale, wheat, barley, oats, and wheat, rye and barley bran. The chemical and amino acid composition of the rapeseed meals from different sources was similar, and effective protein degradability, calculated assuming k=0.05, ranged from 62 to 70%. The effective protein degradability of oilmeals was lower than in the legume seeds and cereal grains. Among cereals, oats had the highest effective protein degradability (92%), the lowest was found in winter barley (75%). The disappearance of total N in the rumen from rapeseed meals was lower than of total amino acids; in the remaining feeds these values were similar. Glutamic acid and arginine were degraded to a greater extent than the remaining amino acids, regardless of the type of feed. Intestinal digestibilities of total N and amino acids of feeds that were less degradable in the rumen, were higher. Cereal starch was degraded in the rumen to a higher extent than starch in legume seeds.