Essential oils combined with exogenous enzymes and vitamin D improved carcass characteristics of confined steers

The experiment was conducted at the Animal Production Center (NUPRAN), Agricultural and Environmental Sciences Sector, Midwestern Parana State University (UNICENTRO), aiming to evaluate the effect of a blend of natural additives compared to a mix of antibiotics commonly used as ruminal fermentation modifiers on the weight gain performance, dry matter intake, feed efficiency, dry matter apparent digestibility and carcass performance of feedlot finished steers. The experiment lasted 112 d, with 28 d for adaptation and 84 d for evaluation, divided into three periods of 28 d each. Thirty-six crossbred steers (Angus × Nellore in equal proportions), whole males, with an average initial weight of 400 ± 14.0 kg and an average age of 12 ± 1 mo, were used. Steers were allotted in 18 pens (2 steers/pen) under a complete randomized block design experiment (9 replications/treatments). Treatments consisted of a basal diet 35:65 forage to-concentrate supplemented as follows: 1- diet with sodium monensin + Virginiamycin (MO + VM), and 2-diet with a blend containing essential oils + exogenous α-amylase + 25-hydroxy-vitamin-D3 (EO + ENZ + HYD). There were no differences between additives tested on the use of different food additives did not change animal performance, which at the end of 84 d of confinement showed an average daily gain of 1.354 kg (P = 0.1709), dry matter intake of 10.39 kg day^-1 (P = 0.7811) and 2.12% of live weight (P = 0.5133), and feed efficiency of 0.137 kg. Steers that receive EO + ENZ + HYD reduced 24% fecal starch (P = 0.0001) and improved the apparent digestibility of DM (1.40%, P = 0.0210), NDF (5.55%, P = 0.0007) and starch (1.30%, P = 0.0001). Animals supplemented with EO + ENZ + HYD showed greater (P = 0.0456) rump fat thickness (12.22 mm) than those supplemented with MO + VM (10.42 mm) at slaughter, and greater marbling and rump fat thickness gain (0.58 points and 5.93 mm) than those supplemented with MO + VM (0.32 points and 7.50 mm) after 84 d of confinement. The blend of essential oils + exogenous α-amylase + 25-hydroxy-vitamin-D3 was effective in replacing the combination of sodium monensin + Virginiamycin on productive performance, apparent digestibility of DM, NDF, and starch, as well as for the disposition of fat in the carcass of steers finished in confinement.