The application of exponential method in the analysis of growth curve for Japanese quail Verwendung der Exponentialmethode zur Analyse der Wachstumskurve Japanischer Wachteln

The growth of animal is measured as body weight on a longitudinal timeframe (AGGREY, 2002) and the characteristic growth curve is obtained in the sigmoid shape by plotting the body weights as function of time (age). The sigmoid shape first shows a self-accelerating phase in which the specific growth rate starts at a value of weight (birth or hatch weight), and then a linear phase follows, which turns into a growth rate to a maximal value in a certain period. Finally, growth curve reaches decelerating phase in which the growth rate decreases and approaches zero which means animal nears mature weight asymptotically (LAWRENCE and FOWLER, 1997). In order to describe growth curves in Japanese quail populations, a number of non-linear models (logistic, Gompertz and Von Bertalanffy) have been used. Growth curve parameters are related with initial weight, growth rate and asymptotic weight. TZENG and BECKER (1981) stated that Logistic and Gompertz models are applicable to avian species under ad-libitum feeding condition. ANTHONY et al. (1986) compared the use of the logistic, Gompertz and Von Bertalanffy equations by transforming the growth curves into linear form in the study of the effects of divergent selection for 4-week body weight on the growth patterns of Japanese quail. The logistic growth function has been applied to chicken data (GROSSMAN and BOHREN, 1982; KNIZETOVA et al., 1991). Also, ANTHONY et al. (1991) compared the growth curves of selected populations in turkey, quail and chicken. Since growth curves shift in response to selection, they are important to breeding plans (BARBATO, 1991; REKAYA et al., 2000). A response to selection altering the shape of the growth curve is feasible. Genetic analysis of growth curves has been applied to body weight-age curves in poultry (BARBATO, 1991). AKBAS and OĞUZ (1998) compared three growth curve models to identify the effect of genetic and environmental factors on the growth curve parameters in quail. The heritabilities of growth curve parameters and phenotypic-genetic correlations were es-