Measurement of Daily Heat Production of Albino Rat from the Insensible Water Loss

Abstract

Summary

I. A method for measurement of the 24 hourly insensible loss of weight of the albino rat has been described. II. The results have shown that the daily heat production of the albino rat can be accurately determined from the weight of the insensible water loss. III. The heat lost by vaporization of water averaged 21.3% of the total calculated heat production in an environmental temperature of 23 to 27°C.

A method is needed for measuring the daily energy requirements of the albino rat. The 24-hour insensible loss of weight and the percentage of the total heat loss that was due to vaporization of water have been measured to ascertain whether or not the measurement of the imperceptible water loss would fulfill this need.

Johnston and Newburgh 1 have applied the method in man. Each rat was placed in a wire cage suspended above a porcelain pan in which the excreta was collected under mineral oil. The weighings were made every 24 to 48 hours on a balance accurate to 200 mg. The weights of the food, water and excreta were obtained from the difference in weight of the container and contents at the beginning and end of the period. The vaporization of water, from the mouth of the water container, averaged 1 gm. per day as measured by a control. The diet of casein 20%, corn starch 48%, lard 16%, cod liver oil 3%, salt mixture (Osborne and Mendell) 5%, dried yeast 8% contained 3.7% moisture but did not lose water at room temperature. The rats’24-hour excreta under oil maintained a constant weight for a week. The temperature of the laboratory varied from 23 to 27°C. Changes in barometric pressure and humidity had no significant influence.

Three grown male rats were studied. The daily food consumption yielded 43.5, 34.6 and 29.7 calories for periods of 42, 29 and 24 days with changes in body weight of only 1.6, 0.5 and 1.0 gm. respectively. In calculating the caloric value of the diet the values 4,4 and 9 were used for carbohydrate, protein and fat.