Relationship between water and food ingestion in the rat

Abstract

Daily observations for 3 months on the ad libitum water-to-food-intake relationship were made on young Sherman male and female rats subsisting on a diet of constant composition, with particular attention being given to the influence on this relationship of handling, weight, and sex. The 1st-week values for water intake in rats not handled prior to experimentation were always higher than subsequent trends and higher than those for previously handled rats. Though water intake increased as body weight increased, this dependence was slight (+.03–.05 ml/g increase in body wt) as contrasted to its dependence upon food intake (+.75 ml/g increase in food ingested). Since the body weight increased faster than the increase in food, the portion of water related to body weight comprised the greater fraction of the total daily water intake. While both absolute intakes continued to increase with time, water intake increased at a greater rate than food ingestion. Thus, the water-to-food ratio gradually increased. These findings obtained for both sexes.