Behaviour of the ewe and lamb at lambing and its relationship to lamb mortality

Abstract

A number of behavioural traits associated with the maternal instinct of sheep were studied under paddock conditions over a range of breeds, age, climate, nutrition and locations in five lambings in south Western and north Western Australia. There was very considerable variation between ewes in any group in the occurrence and timing of each trait. There were few differences due to breed, age of ewe, nutrition, climate or location in the behaviour of the ewe before and during parturition. Nearly all the differences that occurred were in the frequency of pawing the ground before and during labour. Fewer Southdowns and Merinos pawed the ground than ewes of other breeds. Also this trait occurred more in summer than in winter in south Western Australia, and less here than in north Western Australia. The behaviour of the ewe during the post partum period was highly predictable. She normally stood and commenced cleaning within 1 min of birth. Cleaning commenced at the head and progressed down the body. Desertions and other forms of aberrant behaviour were uncommon. There were no biologically significant differences in length of labour, time from birth to stand and time from stand to first drink due to breed, age, pre-lambing nutrition, climatic conditions or location. Second-born twins were delivered after a significantly shorter labour than first-born twins. In one series of observations twins took longer to drink than singles. Type of birth did not influence the time taken for the lamb to stand. Rectal temperature three hours after birth dropped significantly when rainfall exceeded 2 mm during the 3 h. Lamb mortality increased significantly in wet weather in winter and most lambs which died more than 3 h after birth had a depressed rectal temperature at 3 h. The ewes of lambs which died after standing tended to have longer than average labour. Poor maternal behaviour per se was the cause of 16% of lamb deaths and failure of the lamb to drink after standing caused 23% of lamb deaths in winter in south Western Australia. In summer in both environments heat stress was the primary cause of lamb deaths.