AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 5 531-R536, Copyright © 1982 by American Physiological Society
Kinetics of specific food intake and weight gain in rat
S. S. Burkhardt, L. P. Mercer, M. R. Schweisthal and T. B. Cole
We report the expanded application of a recently developed time-invariant
analytic function that relates food intake, growth (weight gain), and
dietary nutrient concentration in the laboratory rat. Data from seven
experiments were utilized, providing analysis of three stages of rat
(Sprague-Dawley) growth (weanling, adult, and pregnant) and a variety of
nutrients: casein, lactalbumin, amino acid mix, thiamin, and pyridoxine.
For each experiment the rats were fed graded levels of a nutrient, ranging
from 0% to a percentage well above the recommended amount, in an otherwise
nutritionally adequate diet. Weight-specific weight gains and food intakes
were calculated for each dietary group and fitted to the Gompertz equation.
The resulting rate constants for each group were identical for weight gain
and food intake. The rate constants were then fitted as functions of
dietary nutrient concentration by the four-parameter mathematical model for
physiological responses. Kinetic rate constants could be characterized as
functions of the dietary concentration of each nutrient tested. This
approach offers new possibilities for the determination and optimization of
dietary requirements. With this approach, one may characterize food intake
and growth in a single rate constant, which varies as a function of dietary
nutrient concentration.
