Water metabolism of Merino sheep shorn during summer

Abstract

Ten Merino wethers in the dry subtropical region of "Gilruth Plains", Cunnamulla, Qld., were shorn in November during a period of sunshine with maximum temperatures between 36 and 38°C. The content, distribution, and turnover of water were estimated before and after shearing. There was no significant change in total body water but the thiocyanate space increased by 12%, the plasma volume by 17%, and the plasma proteins were diluted by 17% after shearing. Water turnover rose from 81.5 to 159 ml/kg/24 hr. There was a correlation (v = 0.68) between the increase in respiratory rate which took place when the sheep were standing in the sun and the increase in water turnover during the same period. It is estimated that an average increment of 1550 kcal/24 hr in heat load from insolation occurred as a result of the removal of fleece during exposure to summer sun. The greater water turnover from evaporative cooling was associated with increased extracellular fluid space.