Stability of exogenous polysaccharide-degrading enzymes in the rumen1

Two commercial preparations of polysaccharide-degrading enzymes (E1 and E2) were tested in vitro and in vivo for rumen stability. In vitro the enzymes were incubated with rumen fluid and the recovery of the remaining substrate-degrading activities (CMC-ase, xylanase and amylase) were followed for up to 6 h (Exp. 1). In vivo the enzyme preparations were introduced directly into the rumen of a lactating dairy cow fed a mixed forage/concentrate diet (Exp. 2). Rumen and duodenal samples were analyzed for substrate-degrading activities (CMC-ase, xylanase, β-glucanase and amylase) for up to 15 h after the enzyme was administered. The tested enzyme preparations were remarkably resistant to microbial fermentation in in vitro conditions. Compared to the control, addition of exogenous enzymes to the rumen increased (P<0.05) the average polysaccharide-degrading activities of the rumen fluid by 169%, 49%, and 61% and 198%, 375%, and 107% for CMC-ase, xylanase and β-glucanase activities, E1 and E2, respectively. The xylanase component of one of the enzymes (E2) partially escaped the reticulo-rumen and the abomasum and increased the xylanase activity of duodenal digesta to 23.3 compared to 0.84 nmol ml−1 min−1 for the control (P<0.05). These data suggest that some exogenous enzymes may by-pass the forestomach and may eventually affect the utilization of nutrients in the small intestine of ruminants.