|Gizzi, Gisele - ADAS NUTRITIONAL SCIENCES|
Submitted to: British Society of Animal Science Occasional Publication Series
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2001
Publication Date: N/A
Technical Abstract: Commercial proteases yield reproducible estimates of rumen protein degradation but, although extent of digestion obtained with commercial proteases is correlated with in situ protein degradation, it has not proven a reliable predictor of rate of protein degradation. If proteolysis in rumen microbes and commercial proteases were correctly characterized, then it would be possible to elaborate protease blends that match the protein degradative activity of the rumen microbes. Incubations were conducted with strained rumen fluid (SRF) and nineteen commercial proteases using fifteen protease substrates, all p-nitroanilide derivatives of amino acids or peptides. Extent of hydrolysis was determined for each substrate, relative to the rate observed for SRF. Rates of hydrolysis of two substrates in SRF were not different from zero, so the remaining 13 substrates were used to characterize activity in SRF and the 19 commercial proteases. Nine proteases had very little activity toward any substrate. Four proteases had activity toward only one substrate and six proteases had significant activity toward 2-10 substrates. A complementary pattern was found for pancreatin and Aspergillus oryzae protease: together, they hydrolysed all 13 substrates. However, mixing enough Aspergillus oryzae and pancreatin to yield a blend with the lowest relative activity equal to 100% of SRF would result in several activities ranging from about 5 to 30 times that in SRF. These preliminary results show the promise of characterizing proteolytic activity of SRF and commercial proteases for preparing protease blends that mimic mixed rumen microbes.