Use of Yea-Sacc8417 live yeast, monensin and their combination in diets for young Nellore bulls in a feedlot

Abstract Text: The objective of this study was to analyze the effects of different food additives administered solely or combined in diets for 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 66 non-castrated Nellore bulls (387.24±21.17 kg), 22 of which were slaughtered in the course of the experiment (6 at the beginning and 16 right after the adaptation period [25 days]) to measure the empty body weight (EBW) and served as reference animals. The experiment was arranged in a completely randomized blocks design (11 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. The dry matter intake (DMI) was lower (P=0.0798) (8.47 kg DM day^-1) in the treatments containing monensin in relation to control diet (10.20 kg DM day^-1). The yeast supplied alone did not interfere (P>0.10) on DMI. The supply of net energy (NE) by the diet was greater (P=0.0055) in the two treatments containing monensin (1.98 and 1.33 Mcal kg DM^-1 for maintenance and gain, respectively) as compared with the control diet and with yeast alone (1.90 and 1.17 Mcal kg DM^-1 for maintenance and gain, respectively). The average daily gain evaluated as body weight (BW) (1.47 kg day^-1) and as EBW (1.58 kg day^-1) did not differ (P>0.10) among diets, but when evaluated as carcass, the diets with monensin reduced (P<0.10) the values (0.89 kg day^-1) as compared with the others (1.04 kg day^-1). There was no difference (P>0.10) among treatments regarding the final BW (521.01±37.59 kg); however, the diets with monensin reduced (P<0.10) the final carcass weight (293.37 kg) in relation to control diet and the diet with yeast alone (304.96 kg). Live yeast does not change the DMI or performance of young Nellore bulls in a feedlot. Monensin reduces DMI and reduces the carcass weight. Supported by FAPESP and Alltech.

Keywords: carcass, empty body weight, performance