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Effects of an Essential Fatty Acid Deficiency, Pair-Feeding and Level of Dietary Corn Oil on the Hypothalamic-Pituitary-Gonadal Axis and Other Physiological Parameters in the Male Chicken^{1, 2, 3, 4,}

Bioresearch Center, Department of Animal Sciences, Vermont Agricultural Experiment Station, University of Vermont, Burlington, Vermont 05401 and Department of Physiology and Biochemistry, University of Reading, England RG2AJ

Two studies were conducted to observe the effects of an essential fatty acid (EFA) deficiency, added dietary corn oil and pair-feeding on growth, reproduction and other physiological parameters in the mature cockerel. A purified, linoleic acid (LA)-deficient diet (0.01% LA), or additions of 5% (3.01% LA) or 15% (9.04% LA) corn oil, were fed ad libitum from hatching through 24 weeks of age. Reductions in growth, feed consumption, and comb, and testes size, incomplete spermatogenesis, increased tissue eicosatrienoic acid (20:39) and changes in weights of selected internal organs were observed in deficient cockerels. Total pituitary gonadotropic activity was measured by two bioassay procedures and blood luteinizing hormone was measured by radioimmunoassay. By maturity both of these parameters were significantly reduced in deficient chickens. When these chickens were fed diets with 5% or 15% corn oil under pair-feeding or ad libitum conditions from 20 to 24 weeks, the reduced growth, comb and testes size and gonadotropin metabolism appeared to be caused by depressions in appetite and energy intake rather than EFA per se. The degenerate testicular histology of the 20-week old deficient cockerels, while responding fully to the ad libitum intake of the diets containing corn oil, showed only partial rehabilitation of spermatogenesis when diets with either 5% or 15% corn oil were pair-fed. In general, increasing the level of dietary fat from 5% to 15% did not cause many physiological changes.

KEY WORDS: • essential fatty acids • pituitary • gonadotropic hormones • appetite regulation • pair-feeding

¹ Part of a thesis submitted to the Graduate College of the University of Vermont as partial fulfillment of the requirement for the Ph.D. degree.

² Presented in part at the annual meeting of the Federation of American Societies for Experimental Biology, Chicago, Illinois, April 1977, Federation Proc. 36, 1126 (Abstr.).

³ Vermont Agricultural Experiment Station Journal Article No. 379.

⁴ Financial support from Agway, Inc. is greatly appreciated. We are grateful to Commercial Solvents, Hoffman-LaRoche, Inc., and Monsanto Chemical Co., for supplying materials.

⁵ Present address: Ralston Purina Company, Poultry Research Department, Checkerboard Square, St. Louis, Missouri 63188.

Manuscript received 20 September 1977.