Opportunities for genetic improvement of lamb survival

Dataonlambsurvivalandassociatedtraitsinvolvingrecordsfrom15192lambs,6308damsand284siresfrom the Sheep CRC's Information Nucleus were studied. Lamb survival to 3 days of age and to weaning was 85 and 80%, respectively, and heritability (s.e.) was 0.014 0.010 and 0.010 0.010, respectively. Of the 14 traits recorded at birth, time taken for the lamb to bleat, rectal temperature and crown-rump length had the highest genetic correlations with lamb survival to weaning (-0.43 0.32, 0.56 0.33 and -0.38 0.36, respectively). Under selection for a multi-trait objective including net reproduction rate (but not lamb survival), survival was predicted to decline genetically by 0.25 lambs weaned per100lambsborn.year,althoughthiswasreversedtoagainof0.20lambsweanedper100lambsborn.yearbyincludingthe traitinthebreedingobjectiveandusing50half-siband50progenyrecordsperselectioncandidate.Accuracyofselectionfor lamb survival was improved to 0.735 with a selection index of lamb survival to weaning, lamb ease, birth coat score, time taken to bleat, rectal temperature and crown-rump length, with the addition of 50 half-sibs and 50 progeny records per candidate. Our results suggest that unless actively incorporated into breeding objectives, lamb survival may genetically decline; however, gains are possible with direct selection using half-sib and progeny records. The addition of indirect selection criteria for lamb survival can further improve accuracy, up to 93.4%, but requires further investigation.