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.