Course of hatch and developmental changes in thyroid hormone concentration in blood of chicken embryo following in ovo ribofavin supplementation

Abstract

The infuence of ribofavin on the function of the hypothalamo pituitary thyroid axis during chicken embryogenesis is poorlyunderstood. Terefore, examination of the efects of in ovo ribofavin supplementation on the possible linkage between the thyroid glandfunction 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 ribofavin/egg. Blood samples were collected on the 12th, 15th, 18th, and 20th days of embryogenesis. Tyroxine (T4)and triiodothyronine (T3 ) concentrations in plasma samples were determined by radioimmunoassay method. Te time of externalpipping and hatching of each chick as well as the body weights of sampled and newly hatched chicks were recorded. Generally, ribofavinsupplied in ovo did not afect chicken embryo mortality and hatchability; however, a dose of 600 µg of ribofavin/egg had a tendencyto reduce embryo body weight. Chicks exposed to 60 µg of ribofavin/egg hatched 3.7 h earlier in comparison with controls and werecharacterized by a higher synchronization degree of hatching. Both applied doses of ribofavin signifcantly elevated T4 concentrationsin blood plasma of the chicken embryos; however, on day 20 of embryogenesis, both applied doses of ribofavin decreased T3 levels inblood circulation. Te data presented here suggest that ribofavin supplementation at the early stages of embryogenesis markedly afectsembryonic development and infuences thyroid hormone metabolism during the second half of embryogenesis.