Effect of monensin sodium associative to virginiamycin and/or essential oils on the performance of feedlot finished steers

The objective of this study was to evaluate the associative effect of monensin sodium to virginiamycin and/or essential oils on performance, consumption of nutrients and dry matter, apparent digestibility, feeding behavior and carcass characteristics of feedlot finished steers. The experiment lasted 106 days with 10 days of adaptation and 96-day trial, and had 32 crosses angus steers, average age 12 months and average weight of 376 kg, divided into 16 stalls, the weighing took place every 21 days and at the end of the experiment. The treatments consisted of the combination of the following additives to the diet included: Monensin sodium, 200 mg day-1 (MO); Monensin sodium, a dose of 200 mg day-1 + essential oil dose of 1.5g day-1 (MO+EO); Monensin sodium, a dose of 200 mg day-1 + virginiamycin, 200 mg day-1 (MO+VI); Monensin sodium, 200 mg day-1 + essential oil dose of 1.5g day-1 + virginiamycin day, 200 mg day-1 (MO+EO+VI), each treatment had four repetitions, where each repetitions consisted of a bay with two animals. The MO+VI association in relation to MO only increase in average daily gain (ADG) of 24.44%, 22.35%, 21.10% and 17.31% in weighing 42, 63, 84 and 96 days, similar the combination of MO+EO+VI which provided an improvement of 21.94%, 13.59%, 15.45% and 14.75% respectively in the same weightings. The daily carcass gain and carcass overall gain were higher in associations MO+VI and MO+EO+VI and provided an average gain of 16.67 kg more compared to MO and MO+EO. In the parameters feed efficiency, dry matter intake and nutrient expressed in kg day-1 and percentage of live weight were not observed differences (P > 0.05) between treatments. Data on apparent digestibility, feeding behavior and carcass characteristics did not show statistical difference between treatment, except for fat thickness which was higher when associated with any of the additives to the MO, and farm weight was higher in associations containing VI. Associating MO+VI or MO+EO+VI proved to be best in this work compared to MO+EO or only MO in the diets of steers in termination.