Evaluation of a standardized mixture of synbiotic-glyconutrients as a feed additive in steers fed a finishing diet: Site and extent of digestion, ruminal fermentation, and microbial protein synthesis

摘要

Four cannulated Holstein steers (137 +/- 9.7 kg live weight, LW) were used in a 4 x 4 Latin square design to examine the effects of feeding a standardized mixture of synbiotic-glyconutrients (GLY) on the characteristics of site and extent of digestion and ruminal fermentation in steers fed a high-energy diet. Treatments consisted a daily intake of 0, 8, 16 or 24 g of GLY/steer. Supplemental GLY was top dressed and mixed directly with the basal diet at time of feeding. Experiment lasted 84-d with experimental periods of 21-day duration. Supplemental GLY increased, in a quadratic manner, the flow of nonammonia-N and microbial N to the small intestine, and ruminal microbial and protein efficiencies, being maximal (P <= 0.02) at a dosage of 16 g/d. Supplemental GLY did not affect ruminal digestion of organic matter (OM) and neutral detergent fiber (NDF), but linearly decreased (P=0.04) ruminal starch digestion. Postruminal and total tract N digestion was increased, being maximal (P <= 0.02) at 16 g/d dosage level. Supplemental GLY linearly increased (P=0.02) ruminal pH, and tended (P=0.08) to linearly decrease ruminal molar proportion of butyrate without effects on ruminal molar proportion of acetate and propionate. It is concluded that GLY supplementation does not affect the site and extent of digestion of OM and NDF, but enhances net ruminal microbial synthesis and postruminal and total tract N digestion. Supplemental GLY increases ruminal pH and modifies rumen fermentation. The greater response to GLY supplementation was at a dosage of 0.12 g / kg LW (equivalent to a dietary concentration of 0.55% "as-fed" basis).