Abstract
Nonlinear growth models having a three-or four-parameter family were applied to individual body weight data of 5 male African green monkeys for estimating their growth patterns. Body weight was measured from birth to six years of ageand 58to 114 data items per monkey were collected. The average body weight atbirth was 360g with the standard deviation off 25g, 4.54±0.29kg at five years of age, and 4.50 ±0.12kg at six years of age at which point body weight was judged to have reached a plateau. Five growth models (Gompertz, Logistic, Richards, Bertalanffy and Brody) were applied to the growth data in this study. As a result, two (Gompertz and Logistic) of the five models were found applicable to all data from the five monkeys. However, the coefficient of determination (R2) obtained by application of the two models were not so large (0.919±0.05 in Gompertz, 0.889 ± 0.01 in Logistic) . Therefore the data were divided into two groups according to monkey age : the first group being from monkeys between birth and 2 years 10 months of age and the second group was from monkeys older than 2 years 10 months of age. The Gompertz model fitted best the data of the first group in four of the five animals (R2=0.982±0.011) . The age at the inflexion point in the Gompertz model nearly corresponded to the age of weaning. The Logistic model was most suitable for the date of the second group in all five animals (R2=0.955±0.038) . The age at inflexion point of the Logistic equation corresponded approximately with sexual maturation judged on the bases of changes in skin color of the face and scrotum, changes in testicular size and those in concentration of serum testosterone.
