EFFECT OF GONADAL HORMONES, GONADOTROPHINS AND THYROXINE ON PLASMA FREE FATTY ACIDS IN THE DOMESTIC FOWL

Abstract

SUMMARY The effects of oestrogens, testosterone, thyroxine, avian and mammalian gonadotrophins and of fasting, on the plasma free fatty acid (FFA) levels in the domestic fowl were investigated. Oestrogen treatment increased the levels of plasma FFA simultaneously with those of the total lipids and lipophosphoprotein in the immature fowl. Testosterone and thyroxine decreased the levels of plasma lipids and of lipophosphoprotein in the laying fowl, but had no effect upon the levels of plasma FFA in either the immature or laying fowl. Gonadotrophins were without effect upon the plasma FFA in the immature pullet but increased the levels in laying or moulting birds, the increases being accompanied by marked follicular growth. Fastings increased the level of plasma FFA in immature birds, but decreased the levels of FFA and total lipid in laying birds. Injections of large doses of hog anterior pituitary extract were without effect on the plasma FFA in conscious immature pullets but induced marked increases in the plasma FFA and a gross lipaemia in the rabbit. It is considered that the increases in plasma FFA found when the bird comes into lay are an indirect result of ovarian stimulation by pituitary hormones.