ENZYME-ACTIVITIES OF RUMEN SOLID-ADHERENT MICROORGANISMS IN CHRONICALLY UNDERFED EWES

Four ruminally cannulated ewes were used in a series of two crossover designs to investigate the effects of underfeeding and of supplementat ion with slowly degradable protein on polysaccharide and glycoside-deg rading enzyme activities in rumen solid-adherent microorganisms. The e wes were fed twice daily on a hay based diet to satisfy either 1.2 or 0.5 maintenance energy requirements, with or without 125 and 65 g fish meal supplement for the high and the low intakes, respectively. Enzym e preparations were isolated from rumen solid contents 2, 6, and 12 h after feeding. Protein supplementation had no significant effect on th e activity of any of the enzymes measured. The effects of feeding leve l on carboxymethycellulase and xylanase activities were small, the spe cific activity (expressed per mg microbial protein) being slightly inc reased at low intake (P < 0.10). However, beta-D-galactosidase, beta-D -glucosidase, beta-D-xylosidase, and beta-D-cellobiosidase activities were considerably increased with low feeding level (+56 to +70% for sp ecific activities; +31 to +50% when expressed per g dry matter). The a ctivities of all enzymes tested increased significantly with time afte r feeding. The extent of specific activity response to variation of fe eding level was greater for late sampling times than 2 h post-feeding. Ruminal degradation of the dietary hay was not affected by fish meal supplementation, but increased with reduction of feeding level (+59.7 g kg(-1) for neutral detergent fibre during the first 12 h of rumen in cubation; P < 0.001). The higher microbial efficiency associated with greater retention time of feed particles in the rumen may account for the increase in cell wall degradation usually observed when feeding le vel declines.