378 Effects of dietary inclusion of an omega-3 fatty acid-based supplement to developing beef bulls on growth and performance.

Abstract Two experiments were designed to evaluate including an omega-3 fatty acid-based supplement in the basal diet of developing bulls post-weaning. In both experiments, spring-born bull calves of either Angus, Simmental, or Hereford breeding were weaned in September and developed in an automated feed intake management system. Bulls were managed as common groups and individually fed from precision intake management bunks; thus individual bull was considered the experimental unit in both experiments. In experiment 1, in a completely randomized design, bulls (n = 42) were stratified by age and BW and randomly assigned to 1 of 3 treatments with 14 bulls per treatment: 0.0 (CON), 0.22 (MOD), or 0.43 (HI) kg per hd per day (DM basis) of an omega-3-based supplement added to a common corn silage and wet corn gluten feed-based growing diet. Dietary treatments began in December (352 ± 19 kg of initial BW; 292 ± 6.25 d of age) and were applied for approximately 60 d. Data were analyzed using the GLIMMIX procedure of SAS with significance declared at P ≤ 0.05. Initial age and BW were similar among treatments (P ≥ 0.98). Dry matter intake (DMI) did not differ (P = 0.64). Bulls on the HI treatment had greater (P ≤ 0.05) daily gain compared to CON and MOD, although ending BW and gain-to-feed ratio did not differ (P ≥ 0.52). Scrotal circumference (SC) and blood serum fatty acid levels were not influenced (P ≥ 0.67). In experiment 2, bulls (n = 41, 332 ± 14 kg of initial BW; 291 ± 6.25 d of age) received the same supplementation treatments for 80 days applied to an isonitrogenous corn silage and dried distillers grains based diet. No treatment differences were detected for final BW (P = 0.86), average daily gain (P = 0.49), and DMI (P = 0.39). Gain to feed tended to be different (P = 0.08), but SC was not impacted by dietary treatments (P = 0.84). Data suggest incorporating an omega-3 fatty acid based supplement into the basal diet for developing beef bulls improves daily gain without impacting dry matter intake, and scrotal circumference within the level and duration of supplementation in these experiments.