title: Intraruminal supplementation with increasing levels of exogenous polysaccharide-degrading enzymes: effects on nutrient digestion in cattle fed a barley grain diet.
abstract: The effects of supplying increasing ruminal doses of exogenous polysaccharide-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion were studied using eight ruminally cannulated heifers, four of which were also 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 effective degradability of feed DM in situ were increased (quadratic response, P<.001) by enzyme treatment. Ruminal administration of EPDE increased ruminal fluid carboxymethylcellulase and xylanase activities linearly (P<.001) and beta-glucanase activity quadratically (P<.01), decreased (quadratic 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) carboxymethylcellulase, xylanase, and beta-glucanase (P<.01) activities in duodenal digesta. Duodenal amylase activity and reducing sugar concentration were also increased (quadratic responses, P<.001 and P<.05, respectively) by EPDE. Xylanase 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.
authors.affiliation: Agriculture and Agri-Food Canada, Research Centre, Lethbridge, AB Canada.
authors.forename: A N
authors.initials: AN
authors.lastname: Hristov
authors.forename: T A
authors.initials: TA
authors.lastname: McAllister
authors.forename: K J
authors.initials: KJ
authors.lastname: Cheng
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D019587:Dietary Supplements; D004063:Digestion; D004386:Duodenum / Q000201:enzymology; D005243:Feces / Q000201:enzymology; D005285:Fermentation; D006026:Glycoside Hydrolases / Q000378:metabolism*; D001467:Hordeum; D006863:Hydrogen-Ion Concentration; D011134:Polysaccharides / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; D006026:Glycoside Hydrolases