VARIATIONS IN MASS AND ENZYME-ACTIVITY OF RUMEN MICROORGANISMS - EFFECT OF BARLEY AND BUFFER SUPPLEMENTS

Four ruminally cannulated cows were used to investigate effect of barl ey with or without buffer on modifications of mass and enzyme activity in rumen microorganisms. Animals were given restricted feed (80% of a d libitum intake) of 7 kg DM day(-1) and with three successive diets. The diet H consisted of 100% Cocksfoot hay. The diet HB was 65% hay wi th 35% pelleted ground barley with infusion of bicarbonate salt for th e diet HBB. The rumen was sampled before (-1 h) and after feeding (+5 h) to isolate liquid- and solid-associated microbial population. (15)( NH4)(2)SO4 was continuously infused into the rumen as a microbial mark er. For all diets microorganisms associated with particles constituted a mean of 74% of the total rumen microbial mass. The density of micro organisms adherent to particles was similar (P > 0.05) for the differe nt diets and the two sampling times, but fibrolytic enzymes activities (xylanase, CMCase, glycosidases) in this microbial population were ma ximal (P < 0.001) 23 h after feed intake. Xylanase (P < 0.05) and CMCa se (P < 0.01) activities just before feeding varied according to diet; they were highest with diet H and similar between barley supplemented diets. Higher glycosidase activities were measured with diet H and HB B than with diet HB 5 h after feeding.