Sweating response in cattle and its relation to rectal temperature, tolerance of sun and metabolic rate

Abstract

SUMMARYSweating rates were analysed in relation to rectal temperatures of cattle to yield a measure of sweating response within and between animals. The measurements, performed over 36 days, were done in a natural radiant environment on six steers in each of three breeds, Brahman (B), Brahman × Hereford–Shorthorn cross-breds (BX), and Shorthorn (S). Each steer was recorded for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. Sweating response, e.g. the linear slope of the relationship between sweat rate and rectal temperature, was greater for B (294 g/m2. h/°C) than for BX (146 g/m2.h/°C) or S (194 g/m2.h/°C) which did not differ; this helped to explain why the range and mean rectal temperature in B were lower and little affected by environmental heat. Curvilinear models of the sweating response indicated that in the environmental conditions of this study, the limit of sweating for B and BX was not reached, while for S, the sweating response approached a plateau. Between animals, the relationship of sweating response to mean rectal temperature was negative (P < 0·01) and its relationship to the time spent in the sun at pasture positive (P < 0·025). Thus this measure of sweating response was a good indicator of thermoregulatory ability of the cattle. However, the sweating response of the steers did not relate to their grazing time or growth. The reasons for this are discussed. Finally, the sweating response was found to be negatively correlated with metabolic rate between animals within breeds (P < 0·01) and this suggested that it may be difficult to combine the desirable traits of good heat adaptation and high metabolic potential in cattle.

Metabolic and hormonal acclimation to heat stress in domesticated ruminants

“…In particular, these authors reported higher ultimate pH values, lower Warner-Bratzler shear force and darker meat of M. longissimus thoracis in heat-stressed beef cattle when compared with muscle samples collected during the cool season. Finch et al (1982) reported a negative correlation between sweating response and metabolic rate, which illustrates the difficulty in combining heat adaptability characteristics and production traits in cattle. Genetic selection for milk and meat production has reduced heat tolerance Kadzere et al, 2002;Gaughan et al, 2009a).…”

Latent heat loss of Holstein cows in a tropical environment: a prediction model

“…In contrast, under high temperatures the body can gain heat by convection (Gebremedhin & Binxin, 2001); if the environment is characterized by intense solar radiation the body gains large amounts of heat by radiation (Curtis, 1982). In those conditions the ability of the animal to withstand its environment is proportional to its ability to dissipate heat by evaporation from the skin surface as a result of sweating (Finch et al, 1982;McLean, 1963;Maia et al, 2005a) or from the respiratory system by panting (Stevens 1981;Maia et al, 2005b).…”

Advances in Stress Physiology and Bioenergetics of Farm Animals: An Overview

“…Under a low ambient temperature heat loss occur mainly as sensible (conduction convection and radiation) heat due to the increasing temperature difference However, when the environment is characterised by intense solar radiation, the body gains large amounts of heat by radiation (daSilva, 2000). In this condition the ability of the animal to withstand its environment is proportional to its ability to dissipate heat by insensible mode (evaporation from the skin respiratory surface) as a result of sweating (Finch et al, 1982) or from the respiratory system by panting (Stevens 1981). Surface area is one of the important parameters that must be considered in the calculation of heat loss because according to Bergmann's rule, the body size of mammals are large in cold climates and smaller in warm climates.…”