Effects of Environmental Temperature on the Iodine Requirements of Young Chickens

Growth rate of chicks maintained at 32 C was reduced as compared with chicks maintained at 21 C. Environmental temperature did not influence the iodine requirement for growth which appeared to be met with a level of approximately 75 ppb in both environments. Thyroid enlargement was observed in both environments for chicks fed low levels of iodine, but the magnitude of the enlargement was much greater at 21 C than at 32 C. A level of 75 ppb iodine was adequate for normal thyroid size at 32 C, but was inadequate to prevent thyroid enlargement at 21 C.