Abstract The objective was to evaluate the effects of including an omega-3 fatty acid-based supplement in the diet of growing beef bulls and body composition on biological parameters and fertility. Weaned beef bull calves (n = 39) of Angus, Hereford, or Simmental breeding were stratified by BW (CON: 332 ± 50.54 kg; MOD: 334 ± 65.10 kg; HI: 338 ± 34.84 kg) and age (CON: 282 ± 24.6 d: MOD 281 ± 16.1 d: HI 283 ± 26.61 d) and assigned 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 diet at 0.00 (CON), 0.22 (MOD), 0.43 (HI) kg per hd per d (DM basis). Managed as a common group and individually fed in precision intake management bunks, bulls (n = 13 per treatment) were supplemented for 80 d. Testicular and facial thermal images were taken on d 0 and 80, and breeding soundness exams and carcass ultrasound measurements were performed on 80. Temperature measurements in the eye and in 8 different locations of the scrotum were recorded with the aid of a commercial software program (Fluke Corporation, Everett, WA). The scrotal measurements were top and bottom, and then top, middle, and bottom one third of each testis. Temperatures of the different testicular locations were averaged into overall (the entirety of the scrotum) and only locations 1, 2, 3 of both testes. Semen samples were analyzed with the aid of a Hamilton Thorne IVOS® II sperm analyzer. Based on carcass ultrasonography, treatment groups were broken into lean ( 0.60 cm 12th rib fat thickness) and fleshy ( 0.60 cm 12th rib fat thickness). Data were analyzed using the GLIMMIX procedures of SAS with individual bull as the experimental unit. Results showed there was no difference in the percentage of motile and progressively motile sperm cells among treatments at d 80. In addition to that, no significant interactions between 12th rib fat thickness and omega-3 supplementation were observed on eye or testicular temperatures. However, an interaction between rib fat group and omega-3 supplementation were observed for morphology (P = 0.03). HI bulls with 0.60 cm of rib fat had improved morphology while MOD bulls with 0.60 cm of rib fat had greater morphology compared to CON bulls. Data suggest an omega-3 fatty acid-based supplement in the basal diet of developing beef bulls may influence semen quality under dietary levels and duration of feeding in this experiment dependent on body fat. These findings support future work investigating omega-3 supplementation as a strategy to offset impaired semen quality associated with overfeeding and obesity-like metabolism in young bulls.
Costa et al. (2026) studied this question.