Comparison of Non-evaporative Heat Transfer in Different Cattle Breeds

- - - - - - - - - - - - - Absfracf Tissue conductance and non-evaporative heat loss from the skin were determined from measurements of body temperature, evaporative water loss, metabolic rate and heat storage in six steers in each of three breeds, Brahman (B), Brahman x Hereford-Shorthorn (BX) and Shorthorn (S). A group of six steers, two from each breed, remained in a climate room set at 25% overnight, and during the following day all were exposed for 1 h to sequential increases in air temperature (28, 32, 37, 41, 43, 45°C). Each steer was measured at 25°C and after a 30-min exposure to each temperature. Tissue conductance increased with air temperature (T,), reaching maximum values at 41°C, the rate of increase (W m-2 "C-I per degree rise in T,) being for B 3.95, for BX 2.33 and for S 2,09. Between 41 and 45"C, tissue conductance remained constant in B but declined in BX and S with a concurrent increase in heat storage. Mean tissue conductance (W m-2 "C-l) of B was 63.5; BX, 56.1; and S, 47.8, values that were significantly different (P < 0.01). Expressed in terms of metabolic weight, the breed means of tissue conductance (litres O2 h-I W-0'75 'C-l) were also significantly different: B, 0.56; BX, 0.43; and S, 0.33 (P < 0.005), with the relative differences similar to those calculated per unit area. Breed differences in tissue conductance may be related to variations in ability to redirect blood from the core to the skin. Non-evaporative heat loss comprised 55-65070 of the total heat loss from the skin in all breeds at Ta of 25°C. The remaining heat was lost through sweating. As T, increased and approached skin temperature, non-evaporative heat loss decreased but in B and BX remained 25% of the total heat loss from the skin. S steers, in contrast, sustained little non-evaporative heat loss as Ta increased because sweating rates increased 50% more than that required to dissipate the heat at the skin. The increase in absolute humidity of the chamber was associated with the excessive sweating in this breed.

[1]  I. L. Bennett,et al.  Coat colour in cattle: effect on thermal balance, behaviour and growth, and relationship with coat type , 1984, The Journal of Agricultural Science.

[2]  J. Hales,et al.  The microcirculation and sweating in isolated perfused horse and ox skin , 1983 .

[3]  C. Glasbey,et al.  Body heat storage in steers (Bos taurus) in fluctuating thermal environments , 1983, The Journal of Agricultural Science.

[4]  I. L. Bennett,et al.  Sweating response in cattle and its relation to rectal temperature, tolerance of sun and metabolic rate , 1982, The Journal of Agricultural Science.

[5]  H. Reich,et al.  Sebum output and water metabolism in different genotypes of cattle in hot environments , 1981 .

[6]  S. Seif,et al.  The effects of heat exposure (31°C) on Zebu and Scottish Highland cattle , 1979, International journal of biometeorology.

[7]  G. S. Johnson,et al.  Thermoregulation in Macaca mulatta: a thermal balance study. , 1979, Journal of applied physiology: respiratory, environmental and exercise physiology.

[8]  H. Y. Elder,et al.  Studies on the nature of the peripheral sudomotor control mechanism. , 1978, Journal of anatomy.

[9]  N. Yeates.  The coat and heat retention in cattle: studies in the tropical maritime climate of Fiji , 1977, Journal of Agricultural Sciences.

[10]  J. McLean.  2 – LOSS OF HEAT BY EVAPORATION , 1974 .

[11]  J. McLean,et al.  On the calculation of heat production from open-circuit calorimetric measurements , 1972, British Journal of Nutrition.

[12]  A. Schleger,et al.  Factors determining sweating competence of cattle skin. , 1971, Australian journal of biological sciences.

[13]  J. Hutchinson,et al.  Moisture, its accumulation and site of evaporation in the coats of sweating cattle , 1970, The Journal of Agricultural Science.

[14]  H. Turner,et al.  Sweating rates of cattle in the field and their reaction to diurnal and seasonal changes , 1965 .

[15]  J. McLean,et al.  The effect of heating the hypothalamus and the skin on the rate of moisture vaporization from the skin of the ox (Bos taurus) , 1963, The Journal of physiology.

[16]  T. Allen.  Responses of Zebu, Jersey, and Zebu X Jersey crossbred heifers to rising temperature, with particular reference to sweating , 1962 .

[17]  K. L. Blaxter,et al.  The energy metabolism of ruminants. , 1962 .

[18]  H. Ledger.  A Possible Explanation for Part of the Difference in Heat Tolerance Exhibited by Bos taurus, and Bos indicus Beef Cattle , 1959, Nature.

[19]  C. S. Blyth,et al.  Lack of insulating effect of body fat during exposure to internal and external heat loads. , 1958, Journal of applied physiology.

[20]  H. H. Kibler,et al.  Environmental physiology with special reference to domestic animals. 11. Effects of temperature, 50° to 105° F and 50° to 9° F on heat production and cardiorespiratory activities in Brahman, Jersey and Holstein cows. , 1950 .