Genetic Estimates for Temperament Traits in Sheep Breeds

Summary

Selection for sheep which are better able to adapt to the normal range of production challenges has the potential to yield improvements in both production efficiency and animal welfare. A key component of adaptability is the temperament of the animal. Numerous tests have been developed to assess temperament particularly in cattle, and these are usually based on the measurement of escape and/or avoidance behaviours. Moreover responses to these tests have been shown to be moderately heritable. In contrast, there is very little information about the heritability of temperament in sheep. However, it is reasonable to assume that similar genetic variation exists. In view of this, and the potential benefits through selection for temperament, this study was undertaken to estimate the genetic parameters for temperament and the genetic correlations with production traits.
Two tests, the isolation box test (IBT) and the measurement of flight time (FT), were selected for evaluation during this study. The IBT involved isolating an animal in a 1.5 m (L) x 1.5 m (H) x 0.75 m (W) box and measuring the degree of agitation for 30 seconds. Agitation score was measured objectively via a purpose built agitometer located on the box. The agitation reflects the animal’s inherent fear of isolation but also its capacity to adapt to the isolation challenge. Flight time was measured by recording the time it takes for an animal to break two infrared sensors (1.5 m) on exit from a weigh crate. The principle of both tests is based on the inherent aversion by sheep of being isolated and separated from their conspecifics and close human contact.
The main objective of this study was to collect additional progeny records (n = 12,152) of temperament from wool, maternal and terminal sire flocks and to estimate genetic parameters for the temperament traits and the correlations with important production traits including growth, wool, carcass, reproduction and parasite resistance traits. The genetic analysis revealed that sheep temperament, as defined by the two behavioural tests, was moderately heritable with marginally higher heritability observed for the IBT agitation score (0.30) compared with FT (0.23). The two temperament traits were not highly correlated however, as the genetic correlation between them was only -0.2. This low correlation could mean that different genetic components of temperament are being captured by the two tests. This also needs to be considered if the tests are to be adopted in breeding programs. There were very few significant correlations between the two temperament traits and the production traits. The notable exception here was the moderate positive genetic correlation (0.22) between IBT agitation score and post-weaning faecal egg count. It was recommended that further analysis of the existing SheepGenomics database be undertaken to confirm this association. Furthermore, the results of another MLA project (AHW.085) will determine whether temperament is relevant in the context of maternal behaviour and neonatal lamb survival.
In the mid-term, selection for temperament will facilitate improvements in management and handling ease and the capacity of animals to adapt to production challenges. In addition, selection for less fearful animals will also yield benefits in terms of animal welfare through reductions in injuries during handling. Further analysis of existing databases (SheepGenomics) and the outcomes of other MLA projects (AHW.085) will conclusively determine whether selection for temperament may directly or indirectly influence other production or animal welfare related traits.