Associations between immune competence health and performance of sheep in the Resource Flock

Summary

Genetic selection for production with little emphasis on health can lead to an increase in disease incidence. This trend is observed in many livestock species. Here we describe the development of methodology to assess general immune competence in sheep and demonstrate that immune competence traits are moderately heritable, suggesting reasonable genetic gains can be expected when selecting for immune competence in sheep.

The project explored associations between the resilience traits of immune competence, stress-responsiveness and temperament and important health and production traits in 2613 lambs and 945 adult ewes.

Immune competence was moderately unfavourably correlated with the temperament trait, flight time and moderately positively correlated with haptoglobin responses to the combined effects of vaccination and management induced stress. Favourable genetic correlations between immune competence, internal parasite resistance and several carcase characteristic traits including tenderness and intramuscular fat were observed in lambs. Although unfavourable genetic correlations were observed between immune competence and certain wool traits such as fibre diameter and yield, favourable correlations were observed for other wool traits such as staple strength.

We hypothesis that significant economic benefits can be achieved by selecting for immune competence in sheep, realised through reduced labour and therapeutic costs associated with monitoring and treating for disease, while having favourable impacts on many important production traits in sheep.