Physiology of Turkey Embryos During Pipping and Hatching. III. Thyroid Function ,

Abstract

Metabolic rates, as measured by oxygen consumption and air cell temperatures, increased significantly (P<.01) as pipping and hatching occurred in turkey embryos. Increased metabolic rates were accompanied by significant (P<.01) increases in both circulating plasma thyroxine (T4 ) and triiodothyronine (T3) concentrations. Both T3 and T4 plasma concentrations declined significantly (P<.01) as the poult emerged from the shell, but the T3 /T4 ratio increased.