Water requirements and metabolism were studied in eight each of Barki and Rahmani sheep and eight Baladi goats. The animals were individually housed in the shade in semi-open pens that were located in a non-desert area. The experiments were carried out during spring, summer and winter seasons, and each experiment lasted for 3 weeks during each season. After a preliminary period of 1 week, an 8-day period was then followed during which body weight, daily feed intake and daily drinking water were recorded. Rectal temperature and respiration rate were also recorded in the early morning and late afternoon. Four animals from each group were then weighed and injected intravenously with tritiated water, TOH (001 mCi/kg body weight) and blood samples were collected during a 4-day period to estimate total body water (TBW) and water turnover rate (WTR).
In all seasons studied, the Rahmani sheep had higher TOH disappearance rate (^-values) and WTR and consequently shorter biological half-time (1½) than the Barki. Moreover, the Barki sheep showed less thermal discomfort than the Rahmani particularly during the summer. Although the Rahmani sheep ingested more water than the Barki sheep during the summer, the Rahmani sheep had a lower percentage of TBW and their calculated water loss revealed that they were in negative water balance during this season. Accordingly, the Barki sheep seem to perform better than the Rahmani in newlyreclaimed desert areas. Baladi goats appear to be more adapted to unfavourable environmental conditions than sheep. This is based upon the findings that they had lower k-values, lower WTR, longer tiand higher TBW, than the two breeds of sheep.