Thermoregulation of male sheep of indigenous or exotic breeds in a tropical environment |
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| Institution: | 1. Universidade Federal do Pará, Av. dos Universitários, s/n, Castanhal 68746-360, Brazil;2. Laboratory of Biotechnology and Animal Reproduction, Empresa Brasileira de Pesquisa Agropecuária, Embrapa Pecuária Sudeste, Rod. Washington Luiz, km 234, São Carlos 13560-970, Brazil;3. Instituto de Zootecnia, Centro Avançado de Pesquisa Tecnológica do Agronegócio de Bovinos de Corte, Rod. Carlos Tonanni, km 94, Sertãozinho 14160-900, Brazil;4. Universidade Federal Rural da Amazônia, Av. Presidente Tancredo Neves 2501, Belém 6077-830, Brazil;5. Universidade Federal Fluminense, Rua Vital Brazil, 64, Niterói 24230-340, Brazil;1. Universidade Federal de Lavras, Department Animal Science, University Campus, Postal code 3037, Downtown, CEP 37200000 Lavras, MG, Brazil;2. Instituto Federal Goiano, Rio Verde Campus, Avenue Sul Goiana, Km 01, Postal Code: 75901-970, Rio verde, GO, Brazil;3. Faculdade Metropolitana Unidas, Department Veterinary Medicine, Avenue Morumbi, 501, Morumbi, São Paulo, SP, Brazil;4. Embrapa Embrapa Suínos e Aves, Highway BR 153, Km 110, District de Tamanduá, Postal code 321, CEP 89700991 Concórdia, SC, Brazil;1. Laboratory of Animal Nutrition, Center of Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, São Paulo, Brazil;2. School of Zootecnia, Federal University of Piauí, Campus Professora Cinobelina Elvas, Bom Jesus, Piauí, Brazil;3. Animal Physiology Division, National Institute of Animal Nutrition and Physiology, Adugodi, Bangalore 560030, India;1. Faculdade de Agronomia e Medicina Veterinária, Universidade de Brasília – UnB, Campus Universitário Darcy Ribeiro, ICC-SUL, Brasília/DF, CEP: 70910-900, Brazil;2. Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul – UFRGS, Av. Bento Gonçalves 9090, Porto Alegre/RS, CEP: 91.540-000, Brazil;3. LSIE – Laboratório de Sistemas de Informações Espaciais, Departamento de Geografia, Universidade de Brasília – UnB, Campus Darcy Ribeiro, ICC-Norte, Brasília/DF, CEP: 70910-900, Brazil;4. Embrapa (Brazilian Agricultural Research Corporation), Secretaria de Relações Internacionais (Secretariat of International Afairs), Embrapa Labex US Program. Brasília, DF, Brazil;5. Instituto Nacional de Ciência e Tecnologia – Informação Genético-Sanitária da Pecuária Brasileira (CNPq/INCT/IGSPB), Belo Horizonte/MG, Brazil;1. Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada;2. Department of Theriogenology, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt |
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| Abstract: | Climate change has intensified the frequency of heat waves in the world, thereby exposing farm animals to stressful conditions. For better productive performance it is important to identify the most resilient genotypes. Thus, our objective was to evaluate the thermoregulatory responses of rams of tropical indigenous (Morada Nova and Santa Inês) and exotic breeds (Dorper and Texel), by monitoring the environmental and physiological indicators related to heat tolerance. The experiment was carried out in a tropical climate region (Cwa), in Brazil, for twelve months, which comprised spring, summer, autumn and winter. Thirty-three rams were divided into groups: Morada Nova (MN; n=8, red-coat), Santa Inês (SI; n=9, black-coat), Dorper (DO; n=8, white-coat) and Texel (TX; n=8, white-coat). The microclimatic variables were monitored, and the THI and BGHI comfort indices were calculated. Coat thickness and body surface temperatures were measured monthly, and serum triiodothyronine-T3 measurements and complete blood tests were performed. The physiological variables were evaluated every fifteen days and skin micro-biopsies were performed in the summer and winter for histological evaluation. During the warmer seasons, the THI and BGHI reached values that indicated thermal discomfort. TX showed higher coat thickness throughout the year, increased physiological variables related to thermolysis, and reduced T3 (P < 0.05). The internal temperature was permanently lower in the MN, SI and DO (P < 0.05). The body surface temperatures were affected by the coat characteristics and wool length. Hematological parameters varied in the seasons with the highest thermal conditions (P < 0.05). The MN showed larger sweat glands, while the area occupied by the sweat glands was higher in the SI. The DO showed higher hair density in the summer and winter (P < 0.05). The results indicated that the MN, SI and DO breeds overcome the thermal challenge more easily throughout the seasons due to specific adaptive morphological and physiological characteristics. |
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| Keywords: | Heat stress Thermolysis Infrared thermography Animal welfare |
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