Including resilience in the breeding objective of sustainable Merino sheep

This study examined the effect of including an indicator trait of resilience (log variance of fibre diameter variation (FD_Lnvar)) into a current industry selection index designed to produce sustainable Merino sheep in Australia. A desired gains index was used to estimate the relative contribution of resilience to the index when either maintaining or improving (decreasing) FD_Lnvar by a quarter or half genetic standard deviation over ten years, compared to the standard index. The relative contribution of resilience needed, to achieve these goals, was shown to be 3.5, 12.4 and 25.3% respectively. Adjusting the index to maintain resilience had little impact on production traits, but prioritising higher FD_Lnvar responses reduced gains in key production traits including clean fleece weight and growth.