The genetics of temperament in Merino sheep and relationships with lamb survival

Abstract

Investigations were made into the genetics of several temperament traits in Merino ewes, with particular emphasis on those aspects which might be associated with maternal behaviour at lambing and consequently, the postnatal survival of lambs. If a beneficial relationship between ewe temperament and lamb survival could be established, indirect selection for such a trait may result in increased gain in survival when compared to direct selection. Ewe mothering temperament was a subjective score based on the proximity of the ewe whilst her lamb was tagged and measured the ewes affinity to her lamb, agitation score measured the reactivity of a sheep whilst isolated from flock mates and lastly, flight time calculated the time taken for a sheep to cross two points 1.7m apart after release from a weight crate reflecting aversion to human handling. A data set from over 118 sires, approximately 2000 animals and more than 20,000 records was analysed for estimation of the genetic parameters for these traits and a set of economically important wool production traits. The heritability (±SE) of ewe mothering temperament was 0.35±0.02. Agitation score and flight time were less heritable (0.20±0.05 and 0.12±0.05, respectively). The heritability of litter survival was low (0.09±0.01) and the genetic correlations between this trait and ewe mothering temperament, agitation score and flight time were 0.18±0.08, 0.39±0.18 and 0.09±0.27, respectively. Estimated genetic correlations (rg) between temperament traits and wool traits overall were negligible, with the exception of staple length (wool growth since last shearing) which was negatively correlated to agitation score (rg=-0.26±0.03). The relationship between agitation score and litter survival is predicted to result in a smaller increase in lamb survival than compared to direct selection for the trait itself. Further, if selection is practised for low agitation score, the observed positive relationship would suggest that litter survival may be reduced in future generations. © 2011 Elsevier B.V.