Thyroxin induced moult in domestic hen

Area of Science:

• Endocrinology
• Avian Physiology
• Animal Science

Background:

• Thyroid hormones, like thyroxin (T4), play a crucial role in avian metabolism and physiological processes.
• Understanding the endocrine regulation of molting is essential for poultry management and welfare.

Purpose of the Study:

• To investigate the effects of different thyroxin (T4) doses on egg production, molting, and associated hormonal changes in domestic hens.
• To elucidate the potential synergistic relationship between thyroxin and progesterone in the induction of molting.

Main Methods:

• Two identical experiments were conducted using domestic hens administered low (0.2 mg/animal) or high (0.4 mg/animal) doses of thyroxin (T4) for 21 days.
• Egg production, feather condition, and plasma concentrations of progesterone, oestrone, 17-beta oestradiol, testosterone, and corticosterone were monitored.

Main Results:

• Higher T4 doses significantly reduced egg production, induced feather loss (molting), and led to complete plumage regeneration by day 42.
• Plasma progesterone concentrations increased significantly and continuously in the high-dose group, peaking during intensive feather loss.
• Plasma corticosterone levels increased continuously in molting hens, while oestrone levels decreased during T4 treatment and increased post-treatment, potentially aiding feather growth.

Conclusions:

• Thyroxin (T4) plays a significant role in the endocrine regulation of molting in domestic hens.
• A synergistic interaction between thyroxin and progesterone appears to be important in the molting process.
• Hormonal changes, including increased corticosterone and post-treatment oestrone, are associated with T4-induced molting and regeneration.