PSXI-20 Effects of dietary inclusion of omega-3 fatty acid-based supplement on biological parameters and sperm motility and morphology of developing beef bulls.

Abstract This study was designed to evaluate the effects of including an omega-3 fatty acid-based supplement in the diet of developing beef bulls on biological parameters and fertility. Weaned beef bull calves (n = 39) of Angus, Hereford, or Simmental breeding were stratified by BW and age to one of three dietary treatments in a completely randomized design. Treatments consisted of including an omega-3-based supplement at 1 of 3 levels to a common corn silage-based growing diet in which all diets were formulated to be isonitrogenous. The levels of the omega-3 fatty acid-based supplement consisted of 0.00 (CON), 0.22 (MOD), 0.43 (HI) kg per hd per day (DM basis) and bulls (n = 13 per treatment) were managed as a common group and individually fed in precision intake management bunks with individual bull as the experimental unit. Bulls were supplemented for 80 days starting in late November of 2024 ending in early February 2025 with an average ambient temperature of –0.5 °C. Ration samples were collected weekly. Blood samples were collected on D0, D57, and D80 by coccygeal venipuncture. Three day shrunk body weights were collected and averaged for D0 and D80 with a single day weight on D57. Testicular thermal images were taken on D0 and D80, and breeding soundness exams were performed by trained technicians on D57, D80 and D101. At the end of the supplementation period on D80, bulls in the HI treatment group had a greater (P < 0.01) percentage of morphologically normal sperm cells in the ejaculate than CON, while the MOD bulls had a tendency (P = 0.06) for improved morphology compared to bulls not supplemented with an omega-3 fatty acid-based supplement. Supplementation (P < 0.01) and breed (P < 0.01) had a significant effect on morphology. Breed and age had a significant effect (P < 0.01), while supplementation and BW had a significant effect (P < 0.05) on D80 motility. Scrotal circumference was not impacted (P > 0.05) by breed or supplementation. Age and weight were significant for scrotal circumference at day 80 (P < 0.05). Bulls supplemented with an omega-3 fatty acid based supplement had greater morphology and motility than non-supplemented bulls. Data suggest that dietary incorporation of an omega-3 fatty acid based supplement into the basal diet of young developing beef bulls may influence semen quality parameters under dietary levels and duration of feeding observed in this experiment.