Lamb survival in Australian flocks: a review

Abstract

Lamb survival is known to be a key component of reproductive efficiency in sheep flocks. It has been the subject of a large number of studies over the decades and this review provides an update and insights into the latest understanding of the extent and variability of lamb losses across Australia. The pattern of causes of lamb losses, including dystocia, starvation/exposure, mismothering and predation, are examined. Likewise the importance of birthweight in contributing to such losses is discussed as are strategies for improving lamb survival. The strategies examined include improved ewe nutrition, shelter provision and selection for cold resistance and improved maternal behaviour.

Growth and pre-weaning mortality of Katahdin lamb crosses

“…This is in agreement with results of Matos et al (1993), who found that males and females have similar survival rates, but it does not agree with previous studies both in wool (Sawalha et al, 2007;Hatcher et al, 2009;Everett-Hincks et al, 2014) and hair sheep (Holmøy et al, 2012;Hinch and Brien, 2014), where male lambs had higher mortality than females. Contrary to the above-mentioned studies, Atashi et al (2013) found that Iranian male lambs showed higher survival rate than females.…”

“…This condition is associated with increased risk of lamb loss (Hinch and Brien, 2014;Holmøy et al, 2014). The marked difference in lamb mortality between genotype groups remains unexplained.…”

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

“…Furthermore, the birthweights of the lambs were close to the range of 4.5-5.5 kg, at which maximum survival occurs, and the rectal temperatures and blood glucose concentrations at birth were similar to those reported previously, therefore indicating that the lambs were not at an increased risk of death in the first 72 h of life (Stafford et al 2007;Miller et al 2010;Chniter et al 2013). On average, only 4.6% of lambs born alive died within the first 72 h of life in the present study, which is considerably lower than the expected mortality of 20-30% (Oldham et al 2011;Hawken et al 2012;Hinch and Brien 2014). We therefore expect that the limited number of lamb deaths during this high-risk period was due to the high level of intervention associated with intensive sampling at lambing.…”

“…Lamb birthweight is the greatest contributor to lamb survival and is strongly influenced by ewe nutrition during pregnancy (Oldham et al 2011;Paganoni et al 2014). However, even at the optimal birthweight of 4.5-5.5 kg (Oldham et al 2011;Hinch and Brien 2014), lamb survival to weaning rarely exceeds 90% for singles, 75% for multiples and 60% for triplets (Paganoni et al 2014), suggesting that factors independent of birthweight must also influence lamb survival. Functional innate and adaptive immune deficiencies in neonatal mammals are known to predispose them to infections, and the associated inflammation may cause tissue damage and/or dysfunction and death, particularly in the perinatal period (Firth et al 2005;Futata et al 2012).…”

“…On average, 30% of all lambs born will die before weaning, and ~80% of lamb deaths occur in the first 48-72 h of life (Miller et al 2010;Oldham et al 2011;Hawken et al 2012;Hinch and Brien 2014;Paganoni et al 2014). Lamb birthweight is the greatest contributor to lamb survival and is strongly influenced by ewe nutrition during pregnancy (Oldham et al 2011;Paganoni et al 2014).…”