Moisture, its accumulation and site of evaporation in the coats of sweating cattle

Abstract

SUMMARYMoisture content of the coats of cattle, expressed as the percentage of the dry weight of hair, has been measured in a wide variety of environmental conditions in summer, springand winter. Strips of coat were clipped from 25 Jersey, 15 Zebu x Jersey crossbred and 9 Hereford heifers in a shed, in a climate room under warm, hot dry and hot humid conditions and outdoors both in sun and shade. Moisture content, weight of coat per unit area, depth of coat, skin and rectal temperatures, sweating and respiratory rates, air temperatures and vapour pressures were measured.The mean moisture content of the coats varied in the different environments from 5·8 to 27·5 % and mean sweating rates from 28 to 438 g m-2 h-1. Moisturein summer coats out of doors in the sun averaged 11·2% and was about the same as that outof doors in the shade. In the shed, coat moisture was also low (average 11·8%) and amounted to less than half of the moisture content of clipped hair in equilibrium with a near saturated atmosphere. Herefords that had been fed a low plane ration from winter to summer, retained their long winter coats and these, in summer, had only half the moisture content of the short coats of normally fed Herefords. In the hot room, the moisture content of summer coats was usually higher than out of doors and varied around 18%.The inner part of the coat had more moisture than the outer part and estimates of moisture gradients were made. Calculation of the contribution of sweating to total moisture in indoor environments showed that, at rapid rates of sweating, it was about 8% and was higher in winter andspring coats than in summer coats (Fig. 3). It was estimated that sun and wind reduced the moisture content of summer coats by about 3% in outdoor summer environments. The effect of sun and wind on moisture content of winter coats in the same environment was estimated at nearly 9%.The results suggest that the site of evaporation was at the skin except in very hot humid indoor environments when some free moisture may have been present in the hair.

Heat stress in cattle and the effect of shade on production and behaviour: a review

“…At high humidities, water (Allen et al 1970) or water vapour (Finch 1985) may be trapped in the air spaces between the hairs of Bus taurus coats, and because of the reduced evaporation there is a compensatory rise in sweating rate.…”

Water vapour and heat combine to elicit biting and biting persistence in tsetse

“…G. pallidipes and other savannah species exploit mainly mammals to obtain a blood meal [28,29]. These hosts lose heat and water through their skin [21], creating a humidity gradient between the skin and the environment [20,30,31], equipping these animals with a means of regulating body temperature through evaporation. Indeed, water droplets are formed by aprocrine glands during sweating [32] indicating that the humidity is close to saturation in the air near the skin (>90% at 37°C, 57 hPa).…”

Topically applied myco-acaricides for the control of cattle ticks: overcoming the challenges

“…The relative humidity in the cattle coat is influenced by both temperature of the hair and vapour pressure (Allen et al 1970). The moisture content of the cattle coat can range from 5.8 to 27.5% and this can be influenced by the cattle breed and environmental factors (Allen et al 1970). The study also indicated that in hot environments the relative humidity of the cattle coat could be up to 5.5% above the average moisture content.…”

“…However, it is now believed that the relative humidity of the microenvironment is more critical than the ambient relative humidity with regards to mortality (Inglis et al 2001). The relative humidity in the cattle coat is influenced by both temperature of the hair and vapour pressure (Allen et al 1970). The moisture content of the cattle coat can range from 5.8 to 27.5% and this can be influenced by the cattle breed and environmental factors (Allen et al 1970).…”