Empenamento, niveis hormonais de triiodotironina a tiroxina a temperatura corporal de frangos de corte de diferentes genotipos criados em diferentes condicoes de temperaturaFeathering, triiodothyronine and thyroxine plasma levels and body temperature

摘要

Feather growth, plasmatic levels of T-3 and T-4 and body temperature were evaluated in broiler raised under different temperatures. The two evaluated broiler lines were Cobb-500 and ISA-Label JA57. One hundred and eighty birds of each line were raised under cold, neutral or hot temperatures in a complete randomized design with 3 x 2 factorial scheme (3 temperatures and 2 lines), with 8 repetitions. There was a significant increase in T-3 levels of birds raised under cold temperature but, tinder hot temperature, these levels decresed. Under high temperatures, ISA Label birds showed the higest levels of T-4 The Cobb birds showed significant T-4 decrease under both, cold and hot temperatures, at 42 days of age; and at 21 days of age this decrease was observed only under hot temperature. There was lower feathering at 42 days of age when birds were raised under hot temperature. ISA Label broilers had a better feather growth than those of Cobb line. Birds raised in a hot environment had higher temperature. Cobb broilers had a significant increase in internal temperature when raised under hot conditions. However ISA Label broilers maintained their body and internal temperature, independently of the raising temperature. It was concluded that environmental temperature affects feathering of broiler chickens from lines selected for fast body weight gain, which also showed low heat tolerance, demonstrated by the higher body and internal temperatures.