Effect of Thyroidectomy on Production, Quality, and Composition of Chicken Eggs

THE effects of thyroidectomy on the structure and pigmentation of the plumage and on the rate of growth and fat deposition in fowls have been well defined by a number of researches (Greenwood and Blyth, 1929; Schwarz, 1930; Lektorsky and Kusmina, 1935; Parkes and Selye, 1937; Greenwood and Chu, 1939). Comparatively little was known, however, concerning the function of the thyroid gland in egg formation at the time the work reported in this paper was initiated. Only a single case of thyroidectomy by Lanz (1904), where the hen laid one abnormal 5 gram egg following the operation, was available. Ewald and Rockwell (1890) obtained no evidence that thyroidectomized pigeons were abnormal in any way. Since then, Greenwood and Chu (1939) have reported that thyroidectomy of growing pullets did not affect the age of sexual maturity of several operated birds as compared with the average age at first egg of the . . .