Abstract
The current study investigated the effects of growing ewe lambs to a heavier live weight at breeding on their subsequent reproductive performance and live weight at two and three years of age, and the growth of their progeny to weaning. Two groups of ewe lambs were bred at seven months of age at an average pre-breeding live weight of either 47.9 ± 0.36 kg (Heavy; n = 135) or 44.9 ± 0.49 kg (Control; n = 135). Breeding performance, fertility, litter size, lambing percentage, ewe wither height, live weight, progeny survival, and live weight were recorded at two and three years of age. None of the variables measured differed between the Heavy and Control ewes at either two or three years of age (P > 0.10). This suggests that farmers can breed their Romney-type ewe lambs at an average live weight of 48 kg without any negative impacts on reproductive performance at two or three years of age nor on their progeny's live weight or growth to weaning. Although breeding heavier ewe lambs improved reproductive performance during their first year, further investigations are needed to assess their overall lamb production and efficiency over multiple breeding seasons.
