Use of particle-bound microbial enzyme activity to predict the rate and extent of fibre degradation in the rumen

A. T. Silva, R. J. Wallace, E. R. Orskov

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1. A method was developed for extracting enzymes from micro-organisms closely associated with ammonia-treated straw (NH-S) that had been incubated in nylon bags in the rumen. Incubation of washed straw with 125 ml carbon tetrachloride/l and 20 µg lysozyme/ml for 3 h at 37° gave carboxymethylcellulase (EC; CMCase) and NAD-linked glutamate dehydrogenase (EC; GDH) activities greater than those extracted by sonication. 2. GDH associated with NH-S increased with incubation time and was highest in sheep receiving a high-barley diet. Particle-bound CMCase activity reached a peak between 16 and 24 h and declined thereafter. 3. Particle-bound GDH activity showed no correlation with dry matter (DM) degradation in the rumens of sheep fed on a range of diets. In contrast, CMCase activity after 24 h was highly correlated with DM degradability of the same samples at 24 h (r 0·98) and 48 h (r 0·94). 4. It was concluded that GDH and CMCase can be used as indices of the total population of colonizing rumen micro-organisms and of the fibre-degrading population respectively, and that these enzymes can therefore be used to assess rapidly and with great sensitivity variations in the rumen environment that affect the rate of fibre breakdown.
Original languageEnglish
Pages (from-to)407-415
Number of pages9
JournalBritish Journal of Nutrition
Issue number3
Publication statusPublished - May 1987


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