Lipotropic Effect of Estradiol-17 β in Fed and Fasted Lactating Cows

Abstract

The lipotropic effect of estradiol-17β was measured in seven nonpregnant Holstein-Friesian cows 2 to 5 wk into lactation. The experiment was divided into an initial 3-day control period, 19 days treatment, and 2 days fast. Jugular blood samples were taken twice daily during the control period, the last 2 days of treatment, and the fast. After the control period, four cows received daily injections of estradiol-17β benzoate (15mg) in sesame oil for the remainder of the experiment whereas three cows received injections of sesame oil only. Estradiol-17β did not change triglyceride concentration of plasma during the treatment period but increased it markedly during fast. Estradiol-17β increased the free glycerol concentration of plasma during treatment. Cholesterol concentrations of plasma showed a consistent trend lower in the estradiol group during treatment and fast. No differences were apparent in glucose and blood ketone concentrations. The concentration of insulin in plasma was lower for the estradiol group during treatment. Estradiol-17β appears to have a similar effect on lipid metabolism in dairy cows to other species. However, it exerted a strong lipotropic effect only under fasting.