Fat-Tailed Awassi and German Mutton Merino Sheep Under Semi-Arid Conditions. 1. Total Body Water, its Distribution and Water Turnover

Abstract

SUMMARYThe total body water (TBW), its distribution and water turnover were measured in native fat-tailed Awassi sheep, a breed well adapted to desert conditions, and in imported German Mutton Merino (GMM) sheep, a breed that evolved in a temperate climate, under semi-arid conditions.TBW (tritiated water space;TOH space), extracellular fluid volume (SCN-space) and plasma volume (T·1824 space) were measured during the summer while these sheep grazed natural pasture that remained as dried stem-cured hay and in the winter while they grazed lush natural pasture. No differences were found between the breeds in any of the measurements in both seasons. Within both breeds, the percentage TOH and SCN-spaces were larger in the summer whereas the percentage T·1824 space remained the same.TBW and water turnover were measured in these breeds in eight trials while the sheep grazed native pasture in the autumn, winter and spring, shrubs in the winter and legumes in the summer. Water and shade were freely and easily accessible throughout the grazing period. The TBW was found to be consistently lower in the Awassi, indicating a higher energy reserve. The water turnover in 1/24 h/kg wt.0·82 was found to be higher in the GMM in all trials; the differences ranged between 3 and 28%. However, in only two out of the eight trials were the differences significant. Thus, the water turnoverwas only slightly lower in the Awassi although this breed evolved under Middle Eastern arid and semi-arid regions.