Duration of maternal undernutrition in late gestation determines the reversibility of intrauterine growth restriction in sheep

Objective To determine whether postnatal growth is irreversibley restricted by different periods of severe maternal undernutrition during late pregnan cy. Method Singleton-bearing ewes were allocated to nutritional treatment group s at 105 days of gestation (term 146 days). Control ewes were fed ad libitu m. ('AL20': 13-15 MJ/day for 105-125 days) while restricted ewes were under nourished for 10 days ('UN10': 0.3 MJ/day for 105-115 days) or 20 days ('UN 20': 0.3 MJ/day for 105-115 days then 0.5 MJ/day until day 125). At 125 day s, six ewes per treatment group were killed while the remainder were allowe d to lamb. Ram progeny were killed at 22 months and ewes at 30 months. Results UN20 lambs were smaller than AL20 lambs at 125 days' gestation and at birth (p < 0.05). UN20 rams but not ewes were shorter at weaning (3 mont hs, p < 0.05) and ewes had shorter hind legs (p < 0.05) and less back fat d epth at 30 months (p < 0.08). Adult weights did not differ between treatmen t groups. Conclusions Growth deficits in sheep induced by severe maternal undernutrit ion in late gestation were largely confined to fetal life and most catch-up growth was achieved during early postnatal life.