Flight speed and agitation in weaned lambs: Genetic and non-genetic effects and relationships with carcass quality

Abstract

By identifying sheep with a genetic or environmentally-induced propensity for higher responses to stress, it is possible to manage or select against those sheep to improve the welfare and ease of handling of the entire flock. Previous studies have reported variable estimates of heritability and non-genetic influences on flight speed and agitation, two measures of behavioural reactivity used in Australian sheep research. While the relationships between these tests and a number of aspects of productivity, including maternal performance, wool and milk production and fattening performance, have been assessed, no such investigation has been made of relationships with carcass quality.This study investigated the 2008–2010 cohorts of the Information Nucleus. Eight flocks totalling 11,047 lambs were tested. Flight speed and agitation were measured at 2–6 weeks post-weaning. Lambs were slaughtered between 5 and 14 months of age, with kill dates staggered to reach target carcass weights of 21kg.Low to moderate heritabilities of flight speed (0.11±0.02) and agitation (0.19±0.02) indicate that while there is an inherent component to behaviour as measured in these tests, that component is small. Phenotypic and genetic correlations between flight speed and agitation were low (0.06±0.01 and 0.20±0.10 respectively).Heavier and female lambs were more reactive in both behavioural tests than lighter and male lambs. First cross terminal breed×Merino type lambs were faster in the flight speed test than other types. In one flock, younger lambs were more reactive in the agitation test. The two behavioural traits varied independently within flocks such that flocks with high average flight speeds did not necessarily also have high average agitation scores.Phenotypic and environmental correlations between behaviours (flight speed and agitation) and carcass traits were very weak or non-significant, indicating that stress responses measured during handling shortly after weaning may not be relevant to stress responses at slaughter several months later. Genetic correlations were mostly non-significant or weak, suggesting that selection based on improving behavioural reactivity of lambs should have little to no impact on carcass quality.