The effect of pasture allowance fed to twin- and triplet-bearing ewes in late pregnancy on ewe and lamb behaviour and performance to weaning

This paper investigates whether pasture allowance before and at lambing affects ewe behaviour, lamb behaviour and subsequent twin and triplet lamb performance to weaning. The trial was carried out at Massey University Keeble Farm in New Zealand. At pregnancy scanning, 186 first cycle-mated ewes were identified as carrying twins ( n = 96) or triplets ( n = 90). The ewes were randomly divided into four nutritional treatments (2, 4, 6 and 8 cm post-grazing sward heights). Each treatment was replicated ( n = 12 ewes in each replicate during pregnancy) on two separate blocks. The trial ewes remained on the four nutritional treatments during pregnancy and parturition. The mean lambing date was the 9 September 2002. Within 12 h of birth lambs were weighed, their sex recorded and identified to the ewe. Maternal and lamb behaviours were then recorded for a period of 5 min. Twin litter weight at birth was similar for ewes grazing 2-, 4- and 6-cm sward heights. Increasing pasture allowance from just 2 cm to 4 cm to ewes with triplet litters increased litter weight at birth by 2 kg, increased weight of lamb weaned by 8 kg and improved litter survival to tagging by 4%. Triplet lamb survival to tagging increased by 15% from the lowest pasture allowance to the highest (from 2 cm to 8 cm). Triplet litter survival was similar to twin litter survival at the highest pasture allowance (8 cm; 2000 kg DM/ha). Pasture allowance had a greater effect on lamb behaviour than ewe behaviour and triplets were more affected than twins. Feeding level did not affect Maternal Behaviour Score (MBS); however, MBS was related to a number of lamb behaviours. Ewes on higher pasture allowances were more likely to stay with their litter at the tagging site. Ewes with triplet litters on the 2-cm sward height were further from their litter 5 min after tagging and high-pitch bleated significantly more than ewes on higher swards. These ewes were less likely to make contact with their lamb after tagging. Triplets born on lower pasture allowances were less likely to stand, locate their dam's udder and follow their moving dam. Fewer triplet lambs bleated following tagging and this might be why fewer ewes made contact. Ewes with triplets grazing high pasture allowances in late pregnancy can achieve litter survival rates similar to those with twins. Ewes with triplets require higher pasture allowances to achieve similar production as ewes with twin litters.