VALIDATION OF IN-SITU NITROGEN DEGRADATION MEASUREMENTS - COMPARATIVEPROTEOLYTIC ACTIVITY OF SOLID-ADHERENT MICROORGANISMS ISOLATED FROM RUMEN CONTENT AND NYLON BAGS CONTAINING VARIOUS FEEDS

Four different feeds (corn, rapeseed meal, untreated and formaldehyde treated soybean meal) were incubated in nylon bags in the rumen of thr ee cannulated dairy cows fed twice daily with a 70:30 forage:concentra te diet. After 2, 6 and 23 h incubation time, the solid-adherent micro bial population was isolated from both nylon bags and rumen content, a nd its proteolytic activity against C-14 casein was measured. The diff erences in proteolytic activity between rumen content and bags were sl ight. In the bags, the activity varied with the incubated feeds, but d ifferences between feeds were observed only for longer incubation time s, and thus would not limit the use of the in situ method to character ize feeds nitrogen degradability. (C) 1998 Elsevier Science B.V.