Thermal equilibrium of Nellore cattle in tropical conditions: an investigation of circadian pattern

Autor(es)

de Melo Costa, Cintia Carol ^[1] ; Campos Maia, Alex Sandro ^[1] ; Brown-Brandl, Tami M. ^[2] ; Neto, Marcos Chiquitelli ^[3] ; Carvalho Fonseca, Vinicius de Franca ^[1]

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ Unesp, Sch Agr & Veterinarian Sci, Innovat Grp Anim Biometeorol INOBIO, Access Rd Prof Paulo Donato Castellane W-N, BR-14884900 Jaboticabal, SP - Brazil

^[2] USDA ARS, US Meat Anim Res Ctr, POB 166, Clay Ctr, NE 68933 - USA

^[3] Sao Paulo State Univ Unesp, Sch Nat Sci & Engn, Nucleo Manejo Rac MANERA, Ilha Solteira, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Thermal Biology; v. 74, p. 317-324, MAY 2018.
• Citações Web of Science: 5

Resumo

The aim of this work was to evaluate the diurnal patterns of physiological responses and the thermal regulation of adult Nellore bulls. Six 30-mo-old Nellore bulls (669 +/- 65 kg BW) were randomly assigned to four 6-h periods in a Latin Square design such that measurements of each animal cover a 24-h cycle. Meteorological variables (air temperature, relative humidity, local solar irradiance, ultraviolet radiation, wind speed and black globe temperature) were recorded at regular one-minute intervals with an automated weather station. Respiratory rate, ventilation rate, oxygen, carbon dioxide, methane, saturation pressure, air temperature of the exhaled air, saturation pressure in the air leaving the ventilated capsule placed over the animal surface, hair coat, skin surface and rectal temperature were assessed. The thermal equilibrium was determined according to the principles of the first law of thermodynamics using biophysical equations. Animals were evaluated in an area which was protected from solar radiation, rain, and had a range of ambient air temperature between 20.57 +/- 0.07 and 30.86 +/- 0.07 degrees C. Percentage of O-2 and CO2 in the exhaled air changed moderately (P < 0.0001) throughout the 24 h, which resulted in an average metabolic heat production of 151.45 +/- 13.60 W m(-2). At the largest thermal gradient (T-S - T-A; from 24:00-07:00 h), heat transferred by long wave radiation and surface convection corresponded to near 60% of the metabolism. At 11:00 h the ambient temperature approached 29 degrees C and latent heat became the main way to cool the body. From this time until 17:00 h, cutaneous evaporation represented approximately 53% of total heat loss. In conclusion, results of the present study seem to be a good indicator of lower energy expenditure for body thermal regulation, high heat tolerance and adaptation of Nellore cattle to the tropical environment. (AU)

• Processo FAPESP: 14/11170-7 - Estudo do equilíbrio térmico associado à emissão de CH4 em bovinos Nelore manejados a campo durante o período de 24 horas
• Beneficiário: Cíntia Carol de Melo Costa
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 14/09639-7 - Emissão de metano e termorregulação em bovinos: um estudo da variação circadiana em ambiente tropical
• Beneficiário: Alex Sandro Campos Maia
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Regular