PSIII-1 The effects of maternal diet on ram lamb reproductive characteristics

Abstract Maternal nutrition during gestation and resulting impacts on ram reproduction and epigenetics are poorly understood. We previously reported altered mRNA and epigenetic markers in F1 ram sperm due to poor maternal diet (restricted- and over-feeding) during gestation, yet the multigenerational effects on ram reproduction are unexplored. We hypothesized that F2 offspring born from restricted- and over-fed granddams would exhibit altered reproductive characteristics, and F1 and F2 offspring would display altered circulating concentrations of reproductive hormones. The objectives of this study were to determine the effects of poor maternal diet on 1) the reproductive function of F2 ram offspring, and 2) key reproductive hormones in F1 and F2 offspring. To evaluate these objectives, multiparous Dorset ewes (F0, n = 46) were fed 100% (CON), 60% (RES), or 140% (OVER) of National Research Council requirements from d 30 of gestation through parturition and a control diet during lactation. Offspring are identified as CON-F1 (n = 10 ewes; 12 rams), RES-F1 (n = 13 ewes; 21 rams), and OVER-F1 (n = 16 ewes; 15 rams). The F1 ewes (n = 37) were maintained on a control diet throughout and were bred between 16 and 19 mo of age to establish the F2 generation. Resulting male offspring are referred to as CON-F2 (n = 6 rams), RES-F2 (n = 13 rams), and OVER-F2 (n = 9 rams) in correspondence to the diets of the granddam. Semen samples of F2 rams were collected via electroejaculation at d 248.4 ± 0.36 (collection 1) and d 255.4 ± 0.36 (collection 2). Semen quality (volume, pH, sperm motility, and sperm concentration) was evaluated at both collections using mCASA; iSperm, Aidmics Biotechnology Co., LTD. Scrotal circumference was measured at collection 2. Sperm morphology was determined by contrast microscopy. Testosterone (T) and follicle stimulating hormone (FSH) were measured in F1 and F2 serum samples collected at d 256 ± 0.13 using commercially available kits. Data were analyzed using R Studio with P ≤ 0.05 considered significant and 0.05 < P ≤ 0.10 considered a tendency. An effect of granddam diet was not observed for F2 ram semen volume, pH, sperm motility, sperm concentration, scrotal circumference, nor histological sperm morphology (P ≥ 0.25). An effect of F0 diet was not observed for F1 or F2 offspring serum concentrations of T and FSH (P ≥ 0.28). In our model, F0 diet during gestation did not affect F2 male offspring sperm quality or circulating T and FSH in F1 and F2 generations. However, based on our previous reports that F0 diet altered F1 sperm epigenome, there may be an impact of maternal diet on epigenetic inheritance which warrants further exploration.