Effect of a 3-day fast on stress hormones in sheep with low or high staple strength

Abstract

This study measured hormone concentrations to determine whether sheep with a history of producing sound wool have a greater resistance to the stress of a 3-day fast. Fasting resulted in increased plasma cortisol concentrations and decreased urinary excretion of norepinephrine and dopamine, while excretion of epinephrine was unchanged. The high staple strength sheep had higher urinary excretion of epinephrine before and during the fast, and higher plasma concentrations of cortisol when fed above maintenance after the fast, but both groups responded similarly to the fast. Although fasting affected stress hormones, this did not translate into effects on follicle shutdown or minimum fibre diameter.