An evaluation of the relation between food consumption rate and equilibrium body-weight in male rats.

1. Two experimental approaches were employed to assess the relation between food consumption rate and maintenance requirements in male weanling rats. The first approach involved restricting food intake in rats previously given free access to food from weaning to 59 d of age. The second approach involved restriction of food intake to various levels after weaning. Maintenance requirements (g food/d per g body-weight (W] were estimated by dividing the rate of food consumption by the resulting equilibrium W (EBW) for each animal. In addition, food consumption was partitioned into growth-independent (maintenance) and growth-dependent (gain) components by alternately setting W and specific growth rate (W') to zero in an equation relating food intake rate to W and W'. Coupling coefficients representing maintenance consumption (g food/d per g W) and gain consumption (g food/g gain) were estimated for each animal by least squares. 2. Both techniques for estimating maintenance consumption provided similar estimates within and across experiments, and regardless of when food restriction was imposed or its severity, consumption for maintenance was about 5% W/d. 3. The EBW to which animals in each treatment group aspired was directly proportional to that group's food intake rate. 4. Coventional measures of growth efficiency were also related to food intake; efficiency decreased with decreasing food intake. Partitioning food consumption into maintenance and gain components revealed that as the rate of food intake decreased, the proportion of total intake consumed for maintenance increased. The results suggest that growth efficiency declines during food intake restriction because proportionately more of total intake is used for maintenance, leaving less available for gain.