Sire-line differences in neonatal lamb mortality due to starvation-exposure (diagnosed using basic ‘on farm’ observations) were observed in five trials (1390 lambs in 15 sire-groups). After correcting for variations in lamb birth weight and in the cold challenge experienced by each lamb using logistic regression, sire-line differences in lamb mortality due to starvation-exposure were detected in flocks where the cold challenge and the number of progeny in each sire line was sufficient (P < 0.05). Although sire-line differences in lamb mortality due to starvation-exposure were detected independent of birth weight, the analyses revealed that birth weight is still the largest influence upon lamb mortality due to cold exposure (P < 0.05). These results confirm that due to the large and contradictory role that birth weight has in influencing lamb survival, it is extremely important to record and account for it in any attempt to breed for enhanced lamb survival. The detection of sire-line differences in lamb mortality due to starvation-exposure independent of birth weight could provide a basis to select for improving lamb survival, thus raising the efficiency of lamb production.
Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 186-190, 2005
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