Sire effects on neonatal lamb vigour and following-behaviour

Abstract

The ability of the lamb to maintain contact with the ewe as she moves away from the birth site is critical to the lamb's subsequent survival. If this contact is compromised then lamb loss is likely to occur due to starvation/mismothering. This study uses sires from the Sheep CRC Information Nucleus Flock to compare the effect of selection of sires within the Merino breed for high or low losses due to starvation/mismothering on neonatal lamb vigour. Lamb vigour was measured using conventional measures of time to perform early neonatal behaviours, early physiological measures (rectal temperatures and blood glucose), and performance in a modified barrier test while under physiological stress from cold exposure. Lambs were exposed to cold at a time (4-6 h after birth) when the ewe is likely to be moving away from the birth site and therefore when losses due to starvation/mismothering are likely to begin. Progeny from the high-loss sires were significantly (P< 0.05) slower to attempt to stand, and to stand, than progeny from the no-loss sires and tended to be slower to reach the udder and suckle (P = 0.07). Lambs from the no-loss group also had a significantly (P < 0.01) higher vigour score than the high-loss group. There was no effect of sire group on the performance of lambs in the modified barrier test; however, cold-treated lambs performed poorly in the test compared with control lambs. It was concluded that sire can have an effect on lamb vigour, but it does not necessarily translate into effects on later following-behaviour while under stressful conditions.