Effects of diet supplementation with clove and rosemary essential oils and protected oils (eugenol, thymol and vanillin) on animal performance, carcass characteristics, digestibility, and ingestive behavior activities for Nellore heifers finished in feedlot

This study was carried out to evaluate the influence of essential oils and their blends on animal performance, feed intake, in situ digestibility, ingestive behavior activities, and carcass characteristics for heifers finished in feedlot on a high-grain diet (similar to 65% corn, 25% corn silage, 10% soybean meal). Forty Nellore heifers (initial body weight 297.6 +/- 31.2 kg) were used in the experiment and distributed randomly among individual pens. Dietary treatments based on essential oil additives included: CON - Without essential oil; ROS - Rosemary essential oil; BLE - Protected blend of eugenol, thymol, and vanillin; BCL - Protected blend + clove essential oil; and BRC - Protected blend + rosemary essential oil + clove essential oil. There were no diet effects on initial and final body weights. However, average daily gains, dry matter intakes (kg/d), and dry matter intakes (%BW) were greater (P < 0.05) in heifers fed with BLE, BCL, and BRC diets than in heifers fed with ROS diets. Feed efficiency (gain to feed) was greater (P < 0.0001) in heifers fed the BCL and BRC diets when compared to heifers fed the ROS diet. There were no diet effects on carcass characteristics. In situ digestibility of dry matter and neutral detergent fiber were greater (P < 0.0001) in heifers fed the three blended diets when compared to heifers fed the ROS diet. The addition of essential oils to the diets of heifers did not alter the muscle, fat, or bone percentages in the carcass. For ingestive behavior activities, data on rumination and idleness tended to be altered by diet with increased rumination in heifers fed BRC diet. The addition of 4 g/animal/d of a blend of essential oils to the diets of Nellore heifers improved average daily gain, dry matter intake, feed efficiency, and ingestive behavior activities.