Thyroxine Secretion Rates of Two Strains of New Hampshire Chickens Selected for High and Low Response to Thiouracil

RECENTLY, Pipes et al. (1958) described a radioiodine technique for the in vivo estimation of thyroxine secretion rate in individual fowls. Using this technique, the thyroxine secretion rates were determined in individuals of two strains of New Hampshire chickens selected for several generations on the basis of high and low response to the feeding of thiouracil (herein designated as the high and low lines). Hatching eggs from the low and high lines which had undergone 3 generations of selection were kindly supplied by Dr. C. S. Shaffner of the Poultry Husbandry Department, University of Maryland. The eggs were hatched by the Poultry Husbandry Department of the University of Missouri and raised in our laboratory. The method of producing these two lines of fowls has been reported by El-Ibiary and Shaffner (1950). Shaklee and Shaffner (1952) confirmed that variation in response was influenced by heredity after two generations of selection. Subsequently, . . .