Associative effect of monensin sodium to virginiamycin on the performance of beef steers in the initial feedlot phase

Abstract

The objective was to evaluate the associative effect of monensin sodium to virginiamycin on the performance, dry matter intake, apparent digestibility and ingestive behavior of steers in the initial feedlot phase. The experiment lasted for 30 days, divided into two experimental periods. Thirty-six Angus Nellore steers, non-castrated, with a mean age of 10 months and an average weight of 300 kg, were divided into 18 pens. Animals were assigned to three treatments with six replications each, with the inclusion of the following additives: T1-monensin sodium, dose of 200 mg day-1; T2-monensin sodium, dose of 125 mg day-1 + virginiamycin, dose of 125 mg day-1; and T3-monensin sodium, dose of 200 mg day-1 + virginiamycin, dose of 125 mg day-1. All experimental procedures were previously submitted to the UNICENTRO Committee for Ethics in Animal Experimentation (CEUA), and were approved for execution (Official Letter 021/2019). The combination of monensin sodium with virginiamycin at a dose of 200 mg + 125 mg animal day-1 showed greater (P < 0.05) average daily weight gain (1.919 kg day-1) and better feed conversion (4.27 kg DM kg of weight gain-1) compared to diets with monensin alone (200 mg animal day-1) or monensin combined with virginiamycin (125 mg + 125 mg animal day-1), even with no significant (P> 0.05) difference in DM intake, with a mean value of 7.88 kg animal day-1. Regardless of the isolated or combined supplementation of the additives, no significant differences were detected in the analysis of the feeder and feces scores, ingestive behavior, and rectal temperature or infrared thermography during the evaluation period. The combination of monensin sodium with virginiamycin at 200 mg + 125 mg animal day-1 proved to be efficient in the initial feedlot period, determined by the greater weight gain and better feed conversion observed in this study.