ESTIMATION OF HERITABILITY, GENETIC CORRELATION OF BODY WEIGHT, AND MODELING OF GROWTH CURVE IN TWO CHICKEN STRAINS

: The purpose of this study was to use nonlinear models (NLN)to characterize the growth pattern and estimate the heritability (h 2 ), the genetic (r g ), and phenotypic(r p ) correlation of the body weight (BW) in two distinct genotypes of chicken raising under Egyptian conditions. A data set of 500 chickens with pedigree information was gathered for this study. For this purpose, the BW was measured at hatching (BW0),4 weeks (BW4), 8 weeks (BW8), and 12 weeks (BW 12) of age. Three NLN models (Logistic, Gompertz, and Von Bertalanffy) were used. Using Wombat software, a multi-trait animal model with a restricted maximum likelihood procedure was used to estimate h 2 , r g, and r p for BW.The results showed that Golden Sabahi (GS) had a significantly higher weight than White Leghorn (WL). The growth curve parameters A (mature body weight), B (biological constant), and K (growth rate) were 3989.9, 0.7853, and 0.0624 for WL and 4332.6,0.7897, and 0.0642 for GS in the von Bertalanffy model, 2152.8, 3.8096, and 0.1322 for WL chickens and 2368, 3.8594, and 0.1350 for GS chickens in the Gompertz model, 1304.5, 19.0421, and 0.3382 for WL chickens and 1455.6, 19.6116, and 0.3411 for GS chickens in the logistic model. Three models represented the growth of the two breeds using goodness-of-fit metrics (R2, MSE, and AIC). Heritability estimates of BW at 0, 4, and 8 were higher in GS than WL, while the estimate of BW at 12 weeks of age was almost similar in the both strains GS and WL (0.1). Between BW0 and BW12, there were strong positive genetic and phenotypic correlations compared by the rest of growth traits . Based on the findings of this investigation, we recommend that the two strains can be utilized for selective breeding between the ages of 4 and 8 weeks to increase the overall genetic improvement of growth traits.