The Mobilisation of Fat in Response to Adrenaline Is Greater in Merino Ewes with Higher Breeding Values for Coefficient of Variation of Fibre Diameter

Biological indicators that can be used to predict the sensitivity of animals to environmental changes are of interest to the sheep industry for economic and welfare reasons. The coefficient of variation of fibre diameter (HCVFD) is a potential indicator of environmental sensitivity and tends to be negatively correlated with fatness. To further understand the association of HCVFD with the sensitivity to the environment, exogenous adrenaline was administered to Merino ewes with known breeding values for fleece weight and HCVFD on three occasions throughout the breeding cycle. The mobilisation of fat in response to Adrenaline was greater in high HCVFD ewes and this effect was consistent across pregnancy, lactation and non-breeding states. Merino sheep with low breeding values for HCVFD are likely to mobilise less fat in response to stress and are therefore likely to be less sensitive to changes in the grazing environment. Therefore HCVFD is thus a potential indicator of environmental sensitivity in sheep.