LIFETIME WOOL. 6. PROGENY BIRTH WEIGHTS AND SURVIVAL

摘要

Lamb survival is largely a function of birth weight (BWT) although factors such as type of birth, ewe milk production and ewe mothering ability may also have an effect (Holst et al. 1992). Restricting the level of nutrition to the pregnant ewe can reduce lamb BWT depending on the ewe age and body condition at joining, the timing and severity of the restriction, and nutrition following the restriction (Holst et al. 1986). This paper reports preliminary data from the Lifetime Wool project (Thompson andOldham 2004) on the impact of differential feeding during pregnancy and lactation on the BWT and survival of single-born lambs. Adult Merino ewes (n=1600 (Victoria) and 1400 (Western Australia), liveweight 46 and 47 kg, condition score 2.8 and 2.7) wereartificially inseminated using semen from 4 genetic sources. After insemination, the ewes were fed to achieve a range in liveweight through pregnancy and lactation. Lambs were tagged at birth, and their sex, BWT and dam number recorded. The BWT and mortality (total deaths to 48 h) data from 2 years (2001 and 2002) from the Victorian and Western Australian sites were analysed separately.