title: Thermal equilibrium responses in Guzerat cattle raised under tropical conditions.
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 20Wm(-2) when the air temperature increased from 24 to 34°C. However, the respiratory latent heat flow increased from 10 to 15Wm(-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 2.2Ls(-1) for females and males, respectively.
authors: 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. Electronic address: leandrozc@yahoo.com.br.
authors: Leandro Zuccherato
authors: LZ
authors: Camerro
authors: 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. Electronic address: alex.maia@fcav.unesp.br.
authors: Alex Sandro Campos
authors: AS
authors: Maia
authors: Biology and Animal Science Department, Sao Paulo State University, Ilha Solteira Campus, Monções Street, zip code 15385-000 Ilha Solteira, SP, Brazil. Electronic address: manera@bio.feis.unesp.br.
authors: Marcos Chiquitelli
authors: MC
authors: Neto
authors: 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. Electronic address: cintiacarolmc@yahoo.com.br.
authors: Cintia Carol de Melo
authors: CC
authors: Costa
authors: 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. Electronic address: patric.castro@ymail.com.
authors: Patric André
authors: PA
authors: Castro
mesh_terms: D000064:Acclimatization; D000822:Animal Husbandry; D000818:Animals; D001833:Body Temperature Regulation; D002153:Calorimetry, Indirect / Q000295:instrumentation; D002417:Cattle / Q000502:physiology*; D004867:Equipment Design; D005260:Female; D006358:Hot Temperature; D006813:Humidity; D008297:Male; D014329:Tropical Climate
keywords: Indirect calorimetry; Thermal equilibrium; Thermoregulation