Sensible and latent heat loss from the body surface of Holstein cows in a tropical environment

• Published in: International journal of biometeorology 2005-09, Vol.50 (1), p.17-22
• Main Authors: Maia, A.S.C, daSilva, R.G, Battiston Loureiro, C.M
• Format: Article
• Language: English
• Subjects: Air temperature; Animals; Body Temperature Regulation - physiology; Brazil; Cattle; Cattle - physiology; Evaporation; Female; Heat transfer; Humidity; Latent heat; Mathematical models; Models, Biological; Pasture; Sensible heat; Skin Physiological Phenomena; Temperature; Tropical Climate; Tropical environments; Ventilation
• ISSN: 0020-7128; 1432-1254
• DOI: 10.1007/s00484-005-0267-1

The general principles of the mechanisms of heat transfer are well known, but knowledge of the transition between evaporative and non-evaporative heat loss by Holstein cows in field conditions must be improved, especially for low-latitude environments. With this aim 15 Holstein cows managed in open pasture were observed in a tropical region. The latent heat loss from the body surface of the animals was measured by means of a ventilated capsule, while convective heat transfer was estimated by the theory of convection from a horizontal cylinder and by the long-wave radiation exchange based on the Stefan-Boltzmann law. When the air temperature was between 10 and 36°C the sensible heat transfer varied from 160 to -30 W m-2, while the latent heat loss by cutaneous evaporation increased from 30 to 350 W m-2. Heat loss by cutaneous evaporation accounted for 20-30% of the total heat loss when air temperatures ranged from 10 to 20°C. At air temperatures >30°C cutaneous evaporation becomes the main avenue of heat loss, accounting for approximately 85% of the total heat loss, while the rest is lost by respiratory evaporation.