Divergent Planes of Nutrition Altered Concentrations of Hormones and Metabolites but not Semen Characteristics in Mature Rams

Abstract Objectives were to evaluate impacts of divergent planes of nutrition on body weight (BW), hormone and metabolite concentrations, and semen characteristics in rams. Mature Rambouillet rams (n = 24, BW = 83.1 ± 2.64 kg) were individually housed and randomly assigned to positive (POS; n = 8), maintenance (MAINT; n = 8), or negative (NEG; n = 8) planes of nutrition for 84 d. Rams were fed a common diet with feed allocations adjusted weekly based on BW to achieve targeted weight gain or loss (approximately 12% initial BW). On d 0, 28, 56, and 84, body condition scores (BCS) and scrotal circumference (SC) were recorded, and blood and semen were collected. Blood was analyzed for triiodothyronine (T3), thyroxine (T4), testosterone, insulin-like growth factor-1 (IGF-1), glucose, and non-esterified fatty acids (NEFA). Semen was collected via electroejaculation and analyzed by Computer Assisted Semen Analysis. Data were analyzed with the GLM or MIXED procedure of SAS, with ram as experimental unit and significance determined at P < 0.05. By design, BW was influenced by a treatment × day interaction (P < 0.0001), and daily weight change was greater (P < 0.0001) for POS (0.11 ± 0.011 kg) than MAINT (0.01 ± 0.011 kg), which was greater (P < 0.0001) than NEG (-0.12 ± 0.011 kg). Consequently, BCS, and SC were greater for POS than NEG as evidenced by a treatment × day interaction (P < 0.0001). Concentrations of T3, IGF-1, and NEFA were increased in POS compared with NEG and MAINT by day 84 (P ≤ 0.03), whereas T4, testosterone, and glucose remained unaffected (P ≤ 0.39). No differences were observed among treatments for semen volume/concentration, motility, or morphology (P ≤ 0.49). Collectively, BW, hormone, and metabolites differed among treatments, indicating a potential for epigenetic alterations which could influence offspring outcomes.