| Autor: |
Bueno JPR; Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Uberlândia, Campus Glória, BR 050, km 78 - Sala 209B - CEP, Uberlândia, MG, 38410-337, Brazil. jprbueno@hotmail.com., Gotardo LRM; Programa de Pós-Graduação em Engenharia de Alimentos, Universidade de São Paulo, Campus Fernando Costa, Av. Duque de Caxias Norte, 225 - CEP, Pirassununga, SP, 13635-900, Brazil., Dos Santos AM; Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Uberlândia, Campus Glória, BR 050, km 78 - Sala 209B - CEP, Uberlândia, MG, 38410-337, Brazil., Litz FH; Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Uberlândia, Campus Glória, BR 050, km 78 - Sala 209B - CEP, Uberlândia, MG, 38410-337, Brazil., Olivieri OCL; Médico Veterinário, Uberlândia, Brazil., Alves RLOR; Programa de Pós-Graduação Ciência Animal e Pastagens, ESALQ-USP, Avenida Pádua Dias, 11 - CEP, Piracicaba, SP, 13418-900, Brazil., Moraes CA; Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Uberlândia, Campus Glória, BR 050, km 78 - Sala 209B - CEP, Uberlândia, MG, 38410-337, Brazil., de Mattos Nascimento MRB; Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Uberlândia, Campus Glória, BR 050, km 78 - Sala 209B - CEP, Uberlândia, MG, 38410-337, Brazil. |
| Abstrakt: |
This study determined thyroid hormone (T 3 and T 4 ) serum levels and investigated thyroid gland histology, as well as two broiler strains performance kept at different periods of heat stress. Broilers (560 Cobb Slow™ and 560 Hubbard Flex™) were distributed in control environment (0) reared following the thermal recommendations, and environments 1, 2, and 3 exposed to high temperatures for 1 h, 2 h, and 3 h a day, respectively, from 14 to 42 days old. At 21, 28, 35, and 42 days old, blood samples were collected to determine T 3 and T 4 serum levels. At 42 days old, thyroid glands were removed for histological analyses. The performance was calculated weekly. T 3 levels decreased with age advance, while T 4 serum concentration was higher at 42 days old (23.27 nmol L -1 ) and lower at 28 days old (15.69 nmol L -1 ). The histological sections revealed that thyroid morphology was well preserved. Live weight was higher in Cobb Slow™ (2.97 kg) than Hubbard Flex™ (2.93 kg) broilers at 42 days old. It is possible to conclude that cyclic heat stress exposure for a 3-h period from 14 to 42 days old did not affect performance, thyroid histology, or T 3 and T 4 serum levels. Cobb Slow™ broilers had the best live weight values at slaughtering. With increasing age, T 3 levels decreased and T 4 levels increased for both strains. |
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