Effects of monensin and increasing dose levels of a mixture of essential oil compounds on intake, digestion and growth performance of beef cattle

Two experiments were conducted with beef cattle to evaluate the effects of dietary addition of monensin (Rumensin® premix, MO) and different doses of a mixture of essential oils (Vertan®; EO) on feed intake, growth performance and feed efficiency (exp. 1), nutrient digestibility and N retention (exp. 2). In exp. 1, 20 steers and 20 heifers (Angus × Hereford, initial BW = 369 ± 10 kg) used in a random block design were fed a total mixed ration (TMR) without supplementation (control, CO), or supplemented with MO (33 mg kg DM-1) or EO (2 and 4 g d-1). In exp. 2, five steers (Angus × Hereford, initial BW = 244 ± 4 kg) used in a 5 × 5 Latin square design were fed CO, MO (33 mg kg DM-1), or EO (2, 3, and 4 g d-1). In exp. 1, DM intake was not affected (P > 0.05) by the addition of EO, but it was 10% lower (P 0.05) between cattle fed CO and those fed MO or EO. Feed efficiency (ADG to DM intake ratio) was not affected ...