Abstract

Studies in sheep suggest that ewe-lamb dams produce smaller offspring compared to mature adult ewes. This study was designed to examine the growth trajectory, body composition and carcass characteristics of 48 singleton Romney male progeny born to either ewe-lambs (ELP; n = 17) or adult ewes (AEP; n = 21). Both dam groups were maintained together under commercial grazing conditions during breeding, pregnancy and lactation. After, weaning the ram lambs continued to be managed together under commercial conditions. Ram offspring were weighed and measured at birth. They were subsequently weighed every two months until 11 months of age (d322). At d322, nine ELP and 10 AEP were euthanised and several body-size and composition measurements were taken. The ELP were lighter and smaller (P<0.05) at birth compared with AEP and they remained significantly (P<0.05) lighter until d218. After d218 this difference in live weight became a tendency (P<0.1). Slaughter data revealed that ELP tended (P<0.1) to have more visceral fat than AEP (P<0.05). Similarly, dual-energy X-ray absorptiometry (DXA) was performed on the left hind-leg and showed that AEP tended to have greater (P<0.1) lean mass compared with ELP. Despite the liveweight differences and the tendency towards differences in adiposity observed at slaughter, ram lamb carcass weight and dressing-out percentage were unaffected indicating that ram offspring meat production from ewe-lamb dams is similar to that from mature adult ewes.

MFP, Loureiro, SJ Pain, PR Kenyon, EC Firth, CW Rogers, and HT Blair

Proceedings of the New Zealand Society of Animal Production, Volume 75, Dunedin, 231-234, 2015