Evaporative heat loss in Bos taurus: Do different cattle breeds cope with heat stress in the same way? |
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| Institution: | 1. ICAAM – Instituto de Ciências Agrárias e Ambientais; Universidade de Évora, Apartado 94, Portugal;2. Faculdade de Zootecnia e Engenharia de Alimentos – Universidade de São Paulo, SP, Brazil;3. Departamento de Matemática, Universidade de Évora, Portugal;4. Universidade Estadual Paulista, Campus de Botucatu, SP, Brazil;5. Departamento de Zootecnia, Universidade de Évora, Portugal;1. University of Nebraska-Lincoln, Lincoln, NE 68028, USA;2. Great Plains Veterinary Educational Center, Clay Center, NE 68933, USA;1. State University of Londrina, Animal Science, Londrina, Paraná, Brazil;2. State University of Mato Grosso do Sul, Animal Science, Aquidauana, Mato Grosso do Sul, Brazil;3. Federal University of Mato Grosso do Sul, Animal Science, Campo Grande, Mato Grosso do Sul, Brazil;4. Federal University of Mato Grosso do Sul, Veterinary Science, Campo Grande, Mato Grosso do Sul, Brazil;5. Leibniz Institute for Farm Animal Biology, Institute of Reproductive Biology, Dummerstorf, Germany;1. College of Animal Life Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea;2. Department of Animal and Dairy Science, University of Georgia, 31793-0748 Tifton, United States;2. School of Animal and Biomedical Sciences and Technology, University of Arizona, Tucson 85719;1. CSIRO Agriculture and Food, Queensland Biosciences Precinct, 306 Carmody Rd., St Lucia, Queensland 4067, Australia;2. Agri-Science Queensland (Dairy), Department of Agriculture and Fisheries, at The University of Queensland Gatton Campus, Lawes, Queensland 4343, Australia;3. School of Agriculture and Food Sciences, The University of Queensland, Gatton, Queensland 4343, Australia |
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| Abstract: | The aim of this study was to compare two Portuguese (Alentejana and Mertolenga) and two exotic (Frisian and Limousine) cattle breeds in terms of the relationship between the increase in ambient temperature and the responses of the evaporative heat loss pathways and the effects on homeothermy. In the experiment, six heifers of the Alentejana, Frisian, and Mertolenga breeds and four heifers of the Limousine breed were used. The animals were placed in four temperature levels, the first one under thermoneutral conditions and the other ones with increase levels of thermal stress. When submitted to severe heat stress, the Frisian developed high thermal tachypnea (125 mov/min) and moderate sweating rates (117 g m?2 h?1), which did not prevent an increase in the rectal temperature (from 38.4 °C to 40.0 °C). Moderate increases in rectal temperature were observed in the Alentejana (from 38.8 °C to 39.4 °C) and Limousine (from 38.6 °C to 39.4 °C), especially in the period of highest heat stress. The Limousine showed moderate levels of tachypnea (101 mov/min) while showing the lowest sweating rates. The Alentejana showed significant increases in sweating rate (156 g m?2 h?1) that played a major role in homeothermy. The Mertolenga showed a superior stability of body temperature, even in the period of highest heat stress (from 38.5 °C to 39.1 °C). Uncommonly, the maintenance of homeothermy during moderate heat stress was achieved primarily by intense tachypnea (122 mov/min). The sweating rate remained abnormally low under conditions of moderate heat stress, rising significantly (110 g m?2 h?1) without evidence of stabilization, only when tendency for heat storage occurred. This unusual response of the evaporative heat loss pathways infers a different thermoregulatory strategy, suggesting a different adaptation to semi-arid environment and strong association with water metabolism. |
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| Keywords: | Heat stress Respiratory frequency Sweating rate |
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