The Influence of High Environmental Temperature on Thyroid Size of Domestic Fowl ,

Abstract

Thyroid weights were taken of 240 adult male and female birds of the New Hampshire, White Plymouth Rock and White Leghorn breeds. Half of these birds had been held since hatching in a temperature controlled environment of 90[degree]F and half had been held in an uncontrolled temperature environment. The White Plymouth Rock and New Hampshire males and females held at a high environmental temperature has statistically significant smaller thyroids than similar groups held in variable temperatures. There was no treatment differences in the thyroid weight of the White Leghorns. Ten male and ten female chicks were killed from 12 mating groups so designed that a group of males from each of the 3 breeds from each environment was mated to groups of females from each environment. There was no significant treatment difference in thyroid size of any of the groups of chickens. There was a breed difference in thyroid size of the chicks. The thyroid of chicks sired by New Hampshire males was larger than those sired by White Plymouth Roch or White Leghorn males.