Turkish Journal of Veterinary & Animal Sciences




The influence of riboflavin on the function of the hypothalamo-pituitary-thyroid axis during chicken embryogenesis is poorly understood. Therefore, examination of the effects of in ovo riboflavin supplementation on the possible linkage between the thyroid gland function and chick embryonic development seems to be interesting. Eggs on the sixth day of incubation were injected with 0 (control), 60, or 600 µg of riboflavin/egg. Blood samples were collected on the 12th, 15th, 18th, and 20th days of embryogenesis. Thyroxine (T_4) and triiodothyronine (T_3) concentrations in plasma samples were determined by radioimmunoassay method. The time of external pipping and hatching of each chick as well as the body weights of sampled and newly hatched chicks were recorded. Generally, riboflavin supplied in ovo did not affect chicken embryo mortality and hatchability; however, a dose of 600 µg of riboflavin/egg had a tendency to reduce embryo body weight. Chicks exposed to 60 µg of riboflavin/egg hatched 3.7 h earlier in comparison with controls and were characterized by a higher synchronization degree of hatching. Both applied doses of riboflavin significantly elevated T_4 concentrations in blood plasma of the chicken embryos; however, on day 20 of embryogenesis, both applied doses of riboflavin decreased T_3 levels in blood circulation. The data presented here suggest that riboflavin supplementation at the early stages of embryogenesis markedly affects embryonic development and influences thyroid hormone metabolism during the second half of embryogenesis.

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