Authors : Naoki Goto, Akira Ishikawa and Masaoki Tsudzuki
Abstract: A growth curve analysis was performed with 439 F2 birds from an intercross of the Oh-Shamo (Japanese Large Game) and White Leghorn breeds of chickens. Individual body weight and shank length were measured at every week until 16 weeks of age. The Gompertz and Logistic models were examined to verify a proper growth curve function for both body weight and sank length in each sex. To estimate the curve parameters on both function models, the Nonlinear Fit Platform of JMP 5.01 was used. In the mean of both the body weight and shank length within sex, there was no significant difference at hatch. However, the significant differences appeared after 1 week of age and then the level of differences within sex increased by age in both traits. As the results of mathematical function analyses, both models significantly fitted to the actual growth with >0.96 coefficients of determinations (R2) however, the Gompertz model showed slightly better fitting with 0.99 of R2 on all of traits and sexes. Also, the Gompertz model was able to estimate the closer values to actual mature body weight and shank length than Logistic’s one. The estimated inflecting points had no large deference between the Gompertz and Logistic functions. On the other hand, the growth curve for shank length had the inflecting point at younger age (4-7 weeks of age) than the growth curve for body weight (9-11 weeks of age). The growth speed of bone development estimated by the shank growth curve reached the maximum earlier than the body development. It indicated that the bone and the body have different growth patterns. As the results, the Gompertz model might be a proper growth curve function for growth analysis and the different growth pattern between bone and body may induce the detection of QTLs for bone and body development separately.
Naoki Goto, Akira Ishikawa and Masaoki Tsudzuki, 2011. Growth Curve Analysis for a QTL Resource Family F2 Intercross of the Oh-Shamo and White Leghorn Breeds of Chickens. Journal of Animal and Veterinary Advances, 10: 3207-3211.