Estimation of lamb deaths within 5 days of birth associated with cold weather

Abstract

In eight Australian Merino and crossbred sheep flocks, all lamb deaths were recorded, together with the corresponding weather before and after each case. Deaths on the day of birth were not strongly associated with a high chill index, but deaths in the following 3 days were significantly increased by a high chill index in the period between birth and the relevant day. Losses were greater for multiple-born lambs than singles under all conditions, but there was not a significant interaction of chill index with multiple births. A model is given for the risk of loss of lambs after birth, on the basis of birthweight, sex of the lamb, multiple birth and chill index for the ewe before birth and the lamb after birth. However, some of this information is not available until after the lamb is born, so a model is also given using only information available shortly before birth, namely, the expected chill index and whether pregnancy scanning has identified single or multiple lambs.