Relationship between plasma corticosteroids and weight change in recently parous lactating and dry sheep

Abstract

Twin-bearing ewes were assigned to three treatments at lambing. Treatment 1 was the adult with both lambs retained; treatment 2 was the adult with one lamb retained; and treatment 3 was the adult alone. All sheep were fed on an amount calculated to maintain an adult and one lamb, and consequently animals in treatments 1, 2 and 3 lost, maintained and gained weight respectively. Chronic under-nutrition of the lactating ewe (treatment 1) resulted in a small increase in the maximum corticosteroid binding capacity and a large increase in total corticosteroid levels in peripheral plasma, resulting in a significant increase in biologically active (free) corticosteroid concentrations. In dry sheep (treatment 3) no such increase in free hormone concentration occurred. There was a significant negative relationship between free corticosteroid concentrations and weight change during both the 2-week intervals and the entire 6-week experimental period.