Effect of fat coating on rumen degradation and intestinal digestibility ofsoybean meal

Three rumen and duodenum fistulated dairy cows were used to determine the e ffects of fat and methionine addition to soybean meal on rumen degradation of crude protein: the amino acid pattern and the intestinal digestibility o f undegraded residues. The addition of 10% and 25% fat resulted in lower DM degradation after 8 and 24 h of incubation. Protein degradation was reduce d by 10% fat addition at 8 and 24 h, while 25% fat addition considerably lo wered crude protein disappearance after only 8 h of incubation. A 10% fat a ddition increases the content of essential amino acids in the undegraded re sidue vs. the control, while 25% fat addition only increases the concentrat ion of lysine, histidine and arginine. Standard soybean meal has higher int estinal dry-matter digestibility than fat-coated soybean, probably due to i nterference between the lipid matrix and the enteric enzyme attack which, m ost likely, does not affect the proteolytic enzymes, given the small differ ences in intestinal nitrogen disappearance found among the different soybea n types. (C) 1999 Elsevier Science B.V. All rights reserved.