Respiratory heat loss in the sheep: a comprehensive model

• Published in: International journal of biometeorology Vol. 46; no. 3; pp. 136 - 140
• Main Authors: Silva, R.G. da, LaScala, N. Jr, Lima Filho, A.E, Catharin, M.C
• Format: Journal Article
• Language: English
• Published: United States 01.08.2002
• Subjects: air; air temperature; ambient temperature; Animals; bioclimatology; Body Temperature Regulation - physiology; climate; equations; evaporation; Female; heat transfer; lung function; Meteorological Concepts; Models, Biological; Respiratory Physiological Phenomena; respiratory rate; sheep; Sheep, Domestic - physiology; thermoregulation; tidal volume; Tropical Climate; vapors
• ISSN: 0020-7128; 1432-1254
• DOI: 10.1007/s00484-002-0128-0

A model is presented for the respiratory heat loss in sheep, considering both the sensible heat lost by convection (CR) and the latent heat eliminated by evaporation (ER). A practical method is described for the estimation of the tidal volume as a function of the respiratory rate. Equations for CR and ER are developed and the relative importance of both heat transfer mechanisms is discussed. At air temperatures up to 30 degrees C sheep have the least respiratory heat loss at air vapor pressures above 1.6 kPa. At an ambient temperature of 40 degrees C respiratory loss of sensible heat can be nil; for higher temperatures the transfer by convection is negative and thus heat is gained. Convection is a mechanism of minor importance for the respiratory heat transfer in sheep at environmental temperatures above 30 degrees C. These observations show the importance of respiratory latent heat loss for thermoregulation of sheep in hot climates.