Effects of phenobarbital, dietary protein intake, and ewe liveweight on ovulation rate and concentrations of plasma FSH and hepatic microsomal enzymes

Abstract

Coopworth ewes were differentially fed from December 1985 to April 1986 to produce two liveweight classes: fat (55-60 kg) and thin (40-45 kg). The ewes were then fed on either high-protein (22%) or low-protein (12%) diets, with or without phenobarbital treatment for 10 days commencing on Day 7 of the oestrous cycle. Phenobarbital treatment caused an increase in ovulation rate that was most pronounced in thin ewes and those on the low-protein diet. Ewe liveweight produced an increase in ovulation rate, but increased dietary protein in the particular formulations used had no effect. Hepatic enzyme concentrations were increased by phenobarbital treatment and, to a lesser extent, by dietary protein intake and ewe liveweight. However, these metabolic changes and the increase in ovulation rate were not accompanied by interpretable changes in the plasma FSH concentrations.