The capacity to measure and select livestock that are more resilient to environmental fluctuation is of increasing importance amidst climate change, labour shortages and increasing production demand. Currently, however, there is no consensus on how to quantify resilience, particularly in extensive sheep populations. In this study, we explored the ability to derive resilience indicator traits from fibre diameter variation measured longitudinally (5 mm increments) along the wool staple. Fibre diameter varies in relation to the supply of nutrients to the wool follicles and thereby provides a stable archive of the animal's physiological status across the preceding wool growth period. From this fibre diameter variation, ways to detect and characterise an animal's ability to withstand or be minimally affected by its environment were explored. The heritability estimates of these traits were shown to be low to moderate (0.10 to 0.31), indicating that genetic variation exists for fibre diameter variation measured along the wool staple which may be interpreted as a measure of resilience. The inclusion of such measures in sheep breeding programs has the potential to improve the resilience of sheep to environmental challenges, which may have positive implications for sheep enterprise profitability, health and welfare.

The ability to select sheep which have a greater capacity to overcome environmental fluctuations is topical given the severity of climatic events, labour shortages and increased productive demands (lamb, meat and wool). In this paper, we review the possibility of using variation in fibre diameter (FD), measured along the wool staple as an indicator of how sheep respond to the fluctuations of their environment.