Fat-tailed Awassi and German Mutton Merino sheep under semi-arid conditions: 2. Total body water and water turnover during pregnancy and lactation

The total body water (TBW) and water turnover of fat-tailed Awassi ewes, a dairy breed well adapted to desert conditions, and of German Mutton Merino (GMM) ewes, a mutton breed that evolved in a temperate climate, were measured during the 3rd, 4th and 5th months of pregnancy and during the 1st month of lactation. Measurements were taken under grazing conditions with unrestricted water in a semi-arid region. Both breeds of sheep lost weight during this period. The percentage of TBW increased, especially during the 5th month of pregnancy when the GMM increased their TBW by 5.2 and the Awassi by 1.0. It was concluded that the nutritive intake was not sufficient to supply the increased energy demands and that the ewes were mobilizing body solids, the GMM at a faster rate. The GMM ewes turned over about 20 more water per kg wt.0.82 during pregnancy and lactation than did the Awassi ewes. There was little difference in water turnover between the control and pregnant sheep within either breed during gestation. During lactation the experimental Awassi increased their water turnover by 29 over the control Awassi and the experimental GMM increased their water turnover by 26 over the control GMM. In both breeds the increase in water turnover during lactation was smaller than that found in other lactating semi-arid ruminants and the increase in water turnover during pregnancy and lactation was smaller than that recommended by the Agricultural Research Council (1965).