Differences in food resource allocation in a long-term selection experiment for litter size in mice - 2. Developmental trends in body weight against food intake

In the accompanying paper specific genetic factors for body weight and food intake were identified in non-reproductive male and female mice of a line selected for high litter size at birth (average of 22 born per lifter) and a non-selected control line (average of 10 born per litter). The existence of these factors are indicated by variation in efficiency parameters such a s growth efficiency and maintenance requirements. Residual food intake (RFI ) and Parks' estimates of growth efficiency (AB) and maintenance requiremen ts (MEm) were used to quantify these factors. In the growing period, female s had a higher RFI (are less efficient) than males. At maturity, selected m ice had higher RFI than control mice and selected females had higher RFI th an selected males. AB was higher in selected-line mice than in control-line mice, and higher in males than in females. MEm was higher in selected-line mice than in control-line mice, and higher in females than in males. The r esults indicate the existence of specific genetic factors for both growth e fficiency and maintenance requirements. Selected females may increase RFI i n the adult state to anticipate the metabolically stressful periods of preg nancy and lactation, to support a generically highly increased lifter size.