PS8-12. Effects of Essential Oil Supplementation on Health and Performance of Newly Received Beef Cattle Grazing Bermudagrass.

Abstract Essential oils have been evaluated as natural feed additives due to their potential rumen-modulating and antioxidant properties, which may improve feed efficiency and animal performance. However, health and performance responses to essential oil supplementation in receiving cattle in forage-based systems have been inconsistent. The objective of this study was to assess the health and performance of newly received heifers grazing bermudagrass (Cynodon dactylon) that were limit-fed dried distillers grains (DDGS) with or without a proprietary blend of essential oils. A total of 72 crossbred beef heifers (235.4 ± 0.64 kg) were shipped from a contract facility in Montgomery, AL to the Southwest Research and Extension Center Stocker Unit (Hope, AR). After a holding period of 6 h, animals were ear tagged, administered lutalyse, weighed, and allowed to rest for 48 h prior to the initiation of the study. On d0, cattle were vaccinated against respiratory and clostridial pathogens, de-wormed, and administered metaphylactic tilmicosin. Animals were stratified by weight and assigned to one of two treatment groups: 1) DDGS supplement only (CON; n = 6 paddocks) or 2) DDGS supplement top-dressed with an essential oil blend (EO; 0.50 g/heifer daily; n = 6 paddocks). Treatments were administered over a 42-d period with supplements offered to heifers at a rate of 2.0% body weight (BW). Heifer BW was recorded on d0, d21, and d42 with animal health monitored daily. Average daily gain (ADG), BW, and gain:feed (G:F) were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and block as a random effect. Pasture served as the experimental unit. Morbidity and mortality were analyzed using the GLIMMIX procedure as nonparametric data with binomial distribution. Heifer BW did not differ between groups through the 42-d supplementation period (P > 0.05). However, on a deads-in basis, ADG (P = 0.05) and G:F (P = 0.04) were greater for EO heifers between d22 and d42. Neither ADG or G:F differed between d0 and d21 nor for the duration of the study between treatment groups (P > 0.05). On a deads-out basis, both ADG and G:F were greater for EO heifers between d0 and d21 (P ≤ 0.02) and between d0 and d42 (P ≤ 0.04). Although morbidity and mortality did not differ between treatment groups (P > 0.05), incidences of morbidity in EO heifers occurred earlier in the supplementation period compared to CON heifers (P = 0.001). These results suggest that supplementation with essential oils may improve gain efficiency but did not influence overall health outcomes during the receiving period.