The Effect of Elevated Ambient Temperatures on the Thyroxine Secretion Rate of Chickens

EXPERIMENTAL data indicate that the thyroids of both birds (Hoffman and Shaffner, 1950) and mammals (Dempsey and Astwood, 1943) respond to a cold environment with an increase in the rate at which thyroxine is secreted. Ample evidence is also available on the effect of high ambient temperatures on thyroxine secretion rate in mammals (Pipes and Turner, 1946), however comparable data on birds are not available. Since the normal body temperature of birds is higher (7–9°F. for the chicken) than that of mammals, and since birds have no sweat glands to aid in heat dissipation, it is of interest to estimate thyroxine secretion rate as an indication of thyroid function of birds under “high” environmental temperatures. Basic information of this nature is important as a foundation for an attempt to regulate the adverse effects of high ambient temperatures during the summer months in southern parts of the country. MATERIALS AND …