Intraruminal supplementation with increasing levels of exogenous polysaccharide-degrading enzymes: Effects on nutrient digestion in cattle fed a barley grain diet
An. Hristov et al., Intraruminal supplementation with increasing levels of exogenous polysaccharide-degrading enzymes: Effects on nutrient digestion in cattle fed a barley grain diet, J ANIM SCI, 78(2), 2000, pp. 477-487
The effects of supplying increasing ruminal doses of exogenous polysacchari
de-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion we
re studied using eight ruminally cannulated heifers, four of which were als
o duodenally cannulated, in a replicated Latin square. The heifers were fed
a diet of 85.5% rolled barley grain and 14% barley silage (DM basis), and
once daily they were given intraruminal doses of 0 (Control), 100, 200, or
400 g of a preparation containing polysaccharide-degrading enzymes. Enzyme
treatment decreased ruminal pH (linear, P < .001) and increased ammonia N (
quadratic, P < .001) concentration. The ruminally soluble fraction and effe
ctive degradability of feed DM in situ were increased (quadratic response,
P < .001) by enzyme treatment. Ruminal administration of EPDE increased rum
inal fluid carboxymethylcellulase and xylanase activities linearly (P < .00
1) and beta-glucanase activity quadratically (P < .01), decreased (quadrati
c response, P < .05) ruminal fluid viscosity, and did not affect (P > .05)
ruminal fluid amylase activity. Elevated levels of fibrolytic activities in
the rumen resulted in increased (quadratic, P < .001) carboxymethylcellula
se, xylanase, and beta-glucanase (P < .01) activities in duodenal digesta.
Duodenal amylase activity and reducing sugar concentration were also increa
sed (quadratic responses, P < .001 and P < .05, respectively) by EPDE. Xyla
nase activity of fecal DM was increased linearly (P < .05) with increasing
ruminal EPDE levels. Apparent digestibilities of DM, crude protein, and NDF
were not affected by EPDE supplementation. Enzyme treatment did not affect
(P > .05) urinary excretion of allantoin and uric acid, or concentrations
of glucose and urea in blood.