title: Influence of direct-fed fibrolytic enzymes on diet digestibility and ruminal activity in sheep fed a grass hay-based diet.
abstract: Six rumen-fistulated Merino sheep were used in a crossover design experiment to evaluate the effects of an exogenous fibrolytic enzyme preparation (12 g/d; ENZ), delivered directly into the rumen, on diet digestibility, ruminal fermentation, and microbial protein synthesis. The enzyme contained endoglucanase and xylanase activities. Sheep were fed a mixed grass hay:concentrate (70:30; DM basis) diet at a daily rate of 46.1 g/kg of BW(0.75). Samples of grass hay were incubated in situ in the rumen of each sheep to measure DM and NDF degradation. The supplementation with ENZ did not affect diet digestibility (P = 0.30 to 0.66), urinary excretion of purine derivatives (P = 0.34), ruminal pH (P = 0.46), or concentrations of NH(3)-N (P = 0.69) and total VFA (P = 0.97). In contrast, molar proportion of propionate were greater (P = 0.001) and acetate:propionate ratio was lower (P < 0.001) in ENZ-supplemented sheep. In addition, ENZ supplementation tended to increase (P = 0.06) numbers of cellulolytic bacteria at 4 h after feeding. Both the ruminally insoluble potentially degradable fraction of grass hay DM and its fractional rate of degradation were increased (P = 0.002 and 0.05, respectively) by ENZ treatment. Supplementation with ENZ also increased (P = 0.01 to 0.02) effective and potential degradability of grass hay DM and NDF. Ruminal fluid endoglucanase and xylanase activities were greater (P < 0.001 and 0.03, respectively) in ENZ-supplemented sheep than in control animals. It was found that ENZ supplementation did not affect either exoglucanase (P = 0.12) or amylase (P = 0.83) activity. The results indicate that supplementing ENZ directly into the rumen increased the fibrolytic activity and stimulated the growth of cellulolytic bacteria without a prefeeding feed-enzyme interaction.
authors.affiliation: Departamento de Producción Animal, Universidad de León, 24071 León, Spain.
authors.forename: L A
authors.initials: LA
authors.lastname: Giraldo
authors.forename: M L
authors.initials: ML
authors.lastname: Tejido
authors.forename: M J
authors.initials: MJ
authors.lastname: Ranilla
authors.forename: S
authors.initials: S
authors.lastname: Ramos
authors.forename: M D
authors.initials: MD
authors.lastname: Carro
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002480:Cellulase / Q000008:administration & dosage* / Q000378:metabolism; D015169:Colony Count, Microbial / Q000662:veterinary; D018592:Cross-Over Studies; D004043:Dietary Fiber / Q000008:administration & dosage* / Q000378:metabolism; D004063:Digestion / Q000187:drug effects; D043364:Endo-1,4-beta Xylanases / Q000008:administration & dosage* / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005243:Feces / Q000737:chemistry; D009584:Nitrogen / Q000378:metabolism; D006109:Poaceae; D011897:Random Allocation; D012417:Rumen / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D012756:Sheep / Q000378:metabolism*; D014556:Urine / Q000737:chemistry
chemical_list: D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D002480:Cellulase; D043364:Endo-1,4-beta Xylanases; D009584:Nitrogen