Effects of a source of ruminally degradable protein and monensin on starch digestion in steers fed a high-grain diet

摘要

A digestion trial was conducted to evaluate a source of readily degradable protein and the polyether ionophore monesin on the accumulation of peptides and starch digestion in steers fed a high concentrate diet. Four dietary treatments: (1) urea supplement (urea), (2) soybean meal supplement (SBM), (3) urea plus monensin (urea +), and (4) soybean meal plus monensin (SBM +) were compared in a Latin Square 4 x 4 experimental design using four crossbred steers (BW = 280 ± 34 kg). Feeding SBM (P .05). Monensin decreased apparent organic matter digestion in the rumen (P 10). Ruminal starch digestion, however, tended to be decreased by monensin (P =.18). Total tract digestibilities of OM, NDF, ADF and starch were not affected by source of supplemental N or monensin (P \u3e.10). Supplemental SBM increased the flow of undegraded feed-N (P .10). Microbial efficiency calculated as g bac N/kg OM digested in the rumen was not affected by treatments although a numerical increase (P =.15) was observed with monensin. Microbial efficiency calculated as 9 bac N/kg starch digested in the rumen was improved when steers were fed SBM (P .10). Monensin increased the molar proportions of ruminal propionate when steers were fed urea supplemented diets but not when fed SBM supplemented diets (protein by monensin interaction, P \u3c.001). Neither source of dietary N nor monensin influenced ruminal NH3-N concentrations;Results are interpreted to indicate that accumulation of peptides in rumen fluid did not increase starch digestion. This study found no evidence to support in vitro studies that have shown that non-structural carbohydrate fermenting bacteria benefit from peptides present in the medium.