Body weights, tail lengths, body temperatures, food intakes, & some slaughter data for four strains of mice reared at three different environmental temperatures

Abstract

Four strains of mice which differed in body weight and tail length and the relationship between these two characteristics were reared from 23 to 44 days of age at three environmental temperatures (7 ± l°c, 21 ± 2°c, and 30 ± 3°c), to investigate the importance and interactions of body weight and tail length in heat regulation and growth. In the first experiment body weights, tail lengths, and body temperatures were measured; in the second experiment body weights, weights of tail, pelt, hair, and total body fat, tail lengths, and food intakes were measured. Body weight was more important than tail length for heat regulation in the cold environment (7°c). The two low-body-weight strains had a higher death rate than mice of the high-body-weight strains, and also had lower body temperatures during the early period of exposure. The tail was important for heat regulation in the hot environment (30°c), at least during the early period of exposure, as the two long-tail strains showed a smaller rise in body temperatures than the short-tail strains, and also consumed more food. After correction for body weight differences there were no strain differences for weight of total body fat or for pelt weight, although mice of the high-body-weight strains had a greater weight of fat after exposure to 30°c than did those of 21 °c. Two strains showed differences between the treatment groups for weight of hair, the groups exposed to 7°c having the most and those exposed to 30°c the least. There was a strain × treatment interaction for food intake, but within strains the group exposed to 7°c consumed the most food and those exposed to 30°c the least. The results show genetic differences between the four strains in their ability to adapt themselves to high and low environmental temperatures.