The effect of ovariectomy on liver metabolism and maintenance energy requirement of hens

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Abstract
Six pullets from each of an egg-producing and meat-producing strain were ovariectomized at 12 wk of age. Ovarian regrowth occurred in 2 of the egg-producing and 4 of the meat-producing strain. Measurements of heat production and energy balance were made after peak lay with ovariectomized and sham-operated laying pullets of both strains. Measurements on the ovariectomized pullets were made before and after implantation with estrogen pellets. Within each strain the ME [metabolizable energy] requirements for maintenance (per kg W 0.75) [body weight], determined by linear regression analysis, were similar whether or not the starvation heat production data were included. The ME requirements for maintenance decreased substantially after ovariectomy but subsequent implantation with estrogen pellets did not increase these requirements. Studies of hepatic enzyme activities indicated that the major influence of the mature ovary was on hepatic lipid metabolism. This was exerted through a specific stimulation of lipogenesis rather than a general increase in metabolism.