Supplemental thyroid hormones and hatchability of turkey eggs
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Abstract:
Fertile turkey eggs were injected with thyroid hormones to test the effects of exogenous hormones on hatchability. Physiological doses of thyroxine (T4) and triiodothyronine (T3) of 50 and 25 ng, respectively, injected at setting, depressed hatchability. Conversely, injections of T4 and T3 at 25 days of incubation significantly (P less than .05) improved hatchability. Injections with thyroid-stimulating hormone (TSH) or tyrosine had no significant effect on hatchability when injected at setting or at 25 days of incubation. Injections of thyroid-releasing hormone (TRH) had no effect on hatchability when injected at setting but significantly (P less than .05) improved hatchability when injected at 25 days of incubation. Because T4 and T3 significantly (P less than .05) depressed hatchability when injected whereas TSH and TRH had no effect on hatchability when injected at setting, these data suggest classic negative feedback mechanisms function very early in the embryonic turkey. The improvement in hatchability observed when thyroid hormones were injected at 25 days of incubation offers further evidence that hypothyroidism may be a cause of poor hatchability among turkey eggs.
Insights
Injecting thyroid hormones into turkey eggs affected hatchability differently depending on the timing. Early injections depressed hatchability, while later injections improved it, suggesting potential for treating turkey egg hatchability issues.
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.