The Thyroxine Secretion Rate of Turkey Poults

RESULTS of recent studies involving chickens and ducks suggest a possible close relationship between the secretory rate of the thyroid gland and growth rate and skeletal maturation. Schultze and Turner (1945) found the thyroxine secretion rate on a body weight basis to be higher for White Leghorn cockerels than for White Plymouth Rock cockerels. The growth patterns of the two breeds differ markedly as the White Leghorn has a more rapid early rate of growth and their growth curve levels off sooner. These investigators also found that under the conditions of their experiments Barred Plymouth Rocks had a higher secretion rate than did the White Plymouth Rocks which paralleled differences in their growth rate. However, as was pointed out, differences in the seasons in which the experiments were conducted makes the results of this latter comparison questionable. Also Glazener, Shaffner and Jull (1949) recently demonstrated that fast growing strains of . . .