Effects of prenatal steroid environment on fetal size and morphology in twin sheep

Abstract

Twenty oestrous-synchronised, twin-bearing, 4.5-year-old Border Leicester x Merino ewes were randomly allocated to 2 treatment groups. At Day 60 post coitus, treated ewes were injected intramuscularly with a single 2 mL dose of testosterone propionate (100 mg/mL). Acute prenatal androgen treatment at 60 days post coitus increased female fetal growth to day 100 post coitus (P < 0.05) and individual cotyledon size (P < 0.01). Acute prenatal androgen treatment induced differential growth amongst major organs and increased ponderal index in ovine fetuses of both sexes (P < 0.05). The results indicate that sexual dimorphism in growth responses to changes in the animal's steroid environment occurs in early life and may be established or entrained well before puberty.