Effects of feeding high dosages of vitamin E to laying hens on thyroid hormone concentrations of hatching chicks.
Long-term experimental feeding of 20,000 ppm alpha-tocopheryl acetate to laying hens caused a significant (P < 0.05) decrease in hatching rates as compared to the control group, which was fed a diet containing 19 ppm alpha-tocopherol. When the thyroid hormones in the developing chicks were checked on incubation days 16, 19, 21, and 22, the following results were ascertained: During the latter part of incubation, increases in plasma concentrations of thyroxine and triiodothyronine were observed. No significant differences in hormone concentrations (P > 0.05) between the control and the treatment group were observed during incubation days 16, 19, and 22. However, on the day of hatching (day 21 of incubation) significantly lower (P < 0.05) triiodothyronine concentrations in chick embryos of piped eggs were found in the treatment group. Moreover, thyroxine concentrations in non-piped eggs and in hatched chicks were found to be significantly higher as compared to the control group. Given these results, one concludes that extremely high dosages of vitamin E may affect thyroid hormone concentrations of hatching chicks, and therefore, the chicks might be inhibited in pipping the egg shell. Hypothetically, the hepatic enzyme 5'-monodeiodinase is involved in the mechanism of inhibition.
Engelmann
D
D
Institute of Physiological Chemistry, School of Veterinary Medicine, 30559 Hannover, Germany.
Flachowsky
G
G
Halle
I
I
Sallmann
H P
HP
D000818:Animals; D002645:Chickens / Q000502:physiology*; D004032:Diet; D004625:Embryo, Nonmammalian; D005260:Female; D010063:Ovum / Q000737:chemistry; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D013963:Thyroid Hormones / Q000032:analysis*; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology*
D013963:Thyroid Hormones; D014810:Vitamin E