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101 Heifer plane of nutrition during the prepubertal phase modifies reproductive development in male fetuses

Maternal nutritional perturbation during gestation influences fetal development which, in turn, can affect postnatal growth, gonad development, gamete quality, and health of the offspring. The objective of this study was to determine whether maternal diet during the pre-pubertal phase would induce modifications in future male fetal reproductive development. Angus × Holstein-Friesian heifers (n = 80) with a mean (± s.d.) age of 141 ± 8 d and bodyweight (BW) of 119 ± 23 kg had unrestricted access to a perennial ryegrass dominated sward supplemented with either 0.5 kg of concentrate daily to achieve an average daily gain (ADG) of 0.50 kg (moderate, MOD) or concentrate ad libitum to achieve an ADG of >1.0 kg (high, HI). Heifers were offered these divergent dietary regimens from 4.5 to 8.5 months of age, after which they were all offered a moderate plane of nutrition. Heifers were bred to a synchronised oestrus at a mean age of 502 ± 8.2 d and mean BW of 360 ± 46.7 kg using semen from a single proven sire. Transrectal uterine ultrasonography was carried out 63 days post-AI to determine pregnancy and fetal sex; a cohort of heifers reflective of group average BW and age and carrying male fetuses were slaughtered on Day 100 of gestation (HI: n = 10; MOD: n = 12). Fetal crown–rump length and weight were recorded. One testis was snap frozen for RNA sequencing and the other was processed for stereology. Mean (± s.d.) fetal crown–rump length and weight were 19.5 ± 0.69 cm and 314.6 ± 33.6 g, respectively, and did not differ between groups. RNA sequencing revealed 45 differentially expressed genes (DEGs) between groups, 44 of which were upregulated in the HI group. A total of 29 biochemical pathways were identified as significantly enriched (P < 0.05), six of which were predicted to be involved in the development of the reproductive tract based on several DEGs. Histological analysis revealed greater (P < 0.05) fetal testicular interstitial tissue density in the MOD group and a strong tendency towards increased seminiferous tubule density (P = 0.06) in the HI group. In conclusion, offering a high plane of nutrition during the prepubertal period not only increases the rate of sexual development in the heifer but also induces latent in utero modifications to the testicular development of their subsequent male progeny. The consequences for postnatal development of male progeny remain to be elucidated. This research was supported by Science Foundation Ireland (16/IA/4474).