Supplemental thyroid hormones and hatchability of turkey eggs

Area of Science:

• Reproductive Biology
• Endocrinology
• Avian Science

Background:

• Thyroid hormones play a crucial role in avian development and metabolism.
• Hatchability in turkey eggs can be influenced by various physiological factors.
• The precise role of exogenous thyroid hormones during embryonic development is not fully understood.

Purpose of the Study:

• To investigate the effects of exogenous thyroid hormones and related substances on turkey egg hatchability.
• To determine the impact of hormone administration timing on embryonic development and hatching success.
• To explore the potential involvement of thyroid hormone feedback mechanisms in early turkey embryogenesis.

Main Methods:

• Fertile turkey eggs were injected with thyroxine (T4), triiodothyronine (T3), thyroid-stimulating hormone (TSH), tyrosine, or thyroid-releasing hormone (TRH).
• Injections were administered either at the time of setting or at 25 days of incubation.
• Hatchability rates were statistically analyzed to determine significant effects of the treatments.

Main Results:

• Early injections (at setting) of T4 and T3 significantly depressed hatchability.
• Late injections (at 25 days) of T4 and T3 significantly improved hatchability.
• TSH and tyrosine had no significant effect on hatchability at either injection time; TRH improved hatchability only when injected late.

Conclusions:

• Thyroid hormones exhibit stage-specific effects on turkey embryonic development and hatchability.
• Early embryonic stages appear sensitive to thyroid hormone feedback, suggesting functional negative feedback mechanisms.
• Hypothyroidism during late incubation may contribute to poor hatchability in turkey eggs, indicating potential therapeutic applications.