Lipotropic effect of estradiol-17 beta in fed and fasted lactating cows

The lipotropic effect of estradiol-17 beta 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-17 beta benzoate (15 mg) in sesame oil for the remainder of the experiment whereas three cows received injections of sesame oil only. Estradiol-17 beta did not change triglyceride concentration of plasma during the treatment period but increased it markedly during fast. Estradiol-17 beta 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-17 beta 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.