Ruminal parameters of young Nellore bulls in a feedlot fed Yea-Sacc8417 live yeast, monensin and their combination

Abstract Text: The objective of this study was to analyze the ruminal parameters of young Nellore bulls in a feedlot for 109 days. The treatments consisted of a control diet with monensin sodium (27.0 mg kg DM^-1), a diet with Yea-Sacc⁸⁴¹⁷ live yeast (2.0 g animal^-1) and a diet with the two additives combined. Diets (10.00% sugarcane bagasse, 73.60% ground corn, 6.40% cottonseed, 6.40% soybean meal, 0.26% corn gluten, 0.79% urea and 2.55% mineral mix) varied only in the inclusion of additives. We used 16 non-castrated Nellore bulls (422.00 ± 80.26 kg) cannulated in the rumen. The experiment was arranged in a completely randomized blocks design (four replicates) as a function of the initial body weight. Data were analyzed by the MIXED procedure of SAS software and means were compared by Fisher's test at 10% significance. The animals were kept in individual pens and were considered the experimental unit. Dry matter intake (DMI) did not differ among the studied diets (9.6 kg DM day^-1), and neither did (P > 0.10) the digestibility of DM (65.8%). The rate of intake was also not affected (P > 0.10) by inclusion of additives, and 90.4% was consumed in the first 12 hours after the 1st feed. Monensin sodium increased (P = 0.0150) the selectivity for concentrate (0.8% more concentrate) as compared with the other diets (0.3% more concentrate). Live yeast, alone or combined with monensin, elevated (P = 0.0420) the acetate content in the rumen (58.15%) in relation to control diet and the treatment of monensin alone (56.97%). Monensin not combined with yeast reduced (P = 0.0373) the acetate-to-propionate ratio in the rumen (1.79) over the other diets (2.05). When supplied separately, the additives monensin sodium and live yeast showed lower values (P = 0.0345) for the rumen pH (5.74 and 5.93 for monensin and yeast, respectively) compared with the other diet (6.07). The combination of the additives live yeast and monensin sodium controlled (P = 0.0376) the decrease in the rumen pH 12 hours after the feed (6.08) as compared with the diet with these additives supplied alone. Sodium monensin not combined with live yeast increased (P = 0.0367) the daily fluctuations of rumen pH (0.19) in relation to the other treatments (0.10). The monensin reduces the acetate-to-propionate ration and yeast increase the acetate proportion. The use additives live yeast and monensin sodium combined has an additive effect on the rumen pH. Supported by FAPESP and Alltech.

Keywords: digestibility, intake, ruminal pH