Postprandial variations in the activity of polysaccharide‐degrading enzymes in microbial populations from the digesta solids and liquor fractions of rumen contents

Abstract

The diurnal variations in the specific activities of polysaccharide-degrading enzymes after feeding were monitored in adherent and non-adherent microbial populations separated from bovine rumen liquor and digesta solids. There were marked differences in the activity profiles of the enzymes within the subpopulations. Enzymes involved in the degradation of soluble carbohydrates were more active in the non-adherent populations, and in the liquor phase subpopulation activities increased in the 1-2 h post-feed period. The muralytic enzymes were most active in the adherent population. Specific activities increased by up to 20-fold over the 24 h period, with an initial five-fold increase occurring between 8 h and 12 h after feeding. Enzyme levels in the three non-adherent populations were similar at the end of the postprandial period. In the population recovered from the liquid associated with the digesta particles, however, the activities did not increase until the latter stages of the period, whereas in the non-adherent population from the digesta solids the activities varied little during the diurnal cycle. The numbers of micro-organisms associated with the digesta solids were similar at 2 h and 20 h after feeding; the variations in enzyme levels did not occur as a result of a population increase but were due to increased activities in an established population. The plant cell wall structural polysaccharides were degraded at different rates. There was no appreciable cellulose digestion during the first 8 h of the postprandial period and although hemicellulosic constituents were removed continuously the rate of loss of both polymers was increased in the later stages of the diurnal cycle when enzyme activities were maximal.

Composition, digestibility and particle-associated enzyme activities in rumen digesta as influenced by particle size and time after feeding

“…Although ingested plant materiał is rapidly colonized in the rumen (Cheng et al, 1984), particle-associated enzyme activities increased between 3-12 h after feeding, in agreement with Williams et al (1989). They observed that the number of microorganisms attached to digesta particles were similar at 2 and 20 h after feeding, and the increases in enzyme activity did not occur as a result of increased population but were due to increased activities in an attached population.…”

Cereal supplementation modified the fibrolytic activity but not the structure of the cellulolytic bacterial community associated with rumen solid digesta

“…Since the solid-associated bacterial community is known to constitute the greatest and the most active rumen microbial community with regards to microbial mass and fibrolytic activities [13,15,30], enzyme and community structure were preferentially assessed in this population.…”

Effect of diet, digesta processing, freezing and extraction procedure on some polysaccharide-degrading activities of ruminal contents

“…The tendency of ruminal microorganisms to parti-tion into liquid and particle-associated fractions with varying degrees of affinity (Bauchop 1980) imposes difficulties in obtaining a representative sample for examination of enzyme activities. Polysaccharide-degrading activities differ between the solid and liquid fractions of ruminal contents (Williams et al 1989), depending on the types and quantities of microorganisms associated with each fraction (Hristov and Broderick 1996). Cell lysis with lysozyme (Silva et al 1987;Huhtanen and Khalili 1992;Sprott et al 1994), sonication (Williams and Withers 1993) and freezedrying and grinding (Noziere and Michalet-Doreau 1994) have been proposed as methods for extracting enzymes from ruminal contents.…”