Thermal equilibrium responses in Guzerat cattle raised under tropical conditions |
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| Institution: | 1. Laboratory of Animal Biometeorology, Animal Science Department, Sao Paulo State University, Jaboticabal Campus, Access Avenue Professor Paulo Donato Castellane, zip code 14884-900 Jaboticabal, SP, Brazil;2. Biology and Animal Science Department, Sao Paulo State University, Ilha Solteira Campus, Monções Street, zip code 15385-000 Ilha Solteira, SP, Brazil;1. Departamento de Zootecnia, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, 7712, 91540-000, Porto Alegre, Rio Grande do Sul, Brazil;2. Departamento de Ciência Animal, Universidade do Estado de Santa Catarina (UDESC Avenida Luiz de Camões, 2090, zip code: 88520000), Lages, Santa Catarina, Brazil;3. Departamento de Ciência Animal, Universidade de Brasília, Brasília Campus Universitário Darcy Ribeiro, zip code 70910900, DF, Brazil;4. Instituto de Ciências Biológicas, Universidade Federal do Rio Grande – FURG, Rua Mal. Floriano Peixoto, 2230, zip code 96170000, São Lourenço do Sul, RS, Brazil;1. Animal and Poultry Nutrition Department, Desert Research Center, El-Matareya, 11753, Cairo, Egypt;2. Animal Production Department, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo, Egypt;1. Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium;2. Institute of Animal Science, University of Bonn, Endenicher Allee 15, 53115 Bonn, Germany;1. Department of Livestock and Pasture Science, University of Fort Hare, Private Bag X1314, Alice 5700, Republic of South Africa;2. Department of Biochemistry and Microbiology, University of Fort Hare, Private Bag X1314, Alice 5700, Republic of South Africa |
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| Abstract: | The literature is very sparse regarding research on the thermal equilibrium in Guzerat cattle (Bos indicus) under field conditions. Some factors can modify the physiological response of Guzerat cattle, such as the reactivity of these animals to handling. Thus, the development of a methodology to condition and select Guzerat cattle to acclimate them to the routine collection of data without altering their physiological response was the objective of the preliminary experiment. Furthermore, the animals selected were used in the main experiment to determine their thermal equilibrium according to the thermal environment. For this proposal, the metabolic heat production and heat exchange between the animal and the environment were measured simultaneously in the field with an indirect calorimetry system coupled to a facial mask. The results of the preliminary experiment showed that the respiratory rate could demonstrate that conditioning efficiently reduced the reactivity of the animals to experimental handling. Furthermore, the respiratory rate can be used to select animals with less reactivity. The results of the main experiment demonstrate that the skin, hair-coat surface and expired air temperature depend on the air temperature, whereas the rectal temperature depends on the time of day; consequently, the sensible heat flow was substantially reduced from 70 to 20 W m−2 when the air temperature increased from 24 to 34 °C. However, the respiratory latent heat flow increased from 10 to 15 W m−2 with the same temperature increase. Furthermore, the metabolic heat production remained stable, independent of the variation of the air temperature; however, it was higher in males than in females (by approximately 25%). This fact can be explained by the variation of the ventilation rate, which had a mean value of 1.6 and 2.2 L s−1 for females and males, respectively. |
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| Keywords: | Indirect calorimetry Thermal equilibrium Thermoregulation |
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