Analysis of animal weight gains in chronic toxicity studies.

The growth pattern of an animal or group of animals during a chronic toxicity study can be used in a a number of ways. Perhaps the most important uses are for prediction of future weights and as evidence of toxic effects. In this paper a model for animal weight gain is constructed and analyzed. Tests and interval estimates are constructed for comparison of growth patterns. It is shown that the asymptotic weight limit of a growth curve is a parameter with which meaningful inferences may be made. Finally, the model is applied to experimental data collected at the National Center for Toxicological Research.