Published online by Cambridge University Press: 14 April 2009
The partitioning of digestible energy intake on an ad libitum diet of standard mouse nuts was investigated in mice selected for high and low body weight at eight weeks and in an unselected control population. In selected mice aged from four to six weeks and housed at a temperature of 24·5 °C, almost all their energy intake could be attributed to basic maintenance and the deposition of extra protein and fat. Control mice, however, had an energy intake considerably in excess of their apparent maintenance and growth requirements. It was concluded that the unaccountable energy loss of the control line could be used to increase growth efficiency in the selected lines. The result is analogous to those obtained from studies on normal and obese mouse genotypes and indicates genetic changes in mechanisms controlling the conversion of food energy to heat.
Provision of a nest to reduce thermoregulatory heat production caused a minor reduction in energy intake and a corresponding decrease in the energy discrepancy. There was no effect on growth.