The estimation of genetic parameters for growth curve traits in Raeini Cashmere goat described by Gompertz model

摘要

The objectives of this study were to describe growth curve of Raeini Cashmere goat applying the Gompertz growth model and genetic evaluation of growth curve-related traits including model parameters of A, B and K, inflection age (IA) and inflection weight (IW) under animal model. The data used in this study, collected in Raeini Cashmere goat breeding station from 1997 to 2009 and were included 12,831 body weights records measured at birth, weaning, 6-months of age, 9-month of age and yearling of age. The Pearson's correlation coefficient between observed and predicted body weights was 0.98, which means that Gompertz model adequately described the growth curve in Raeini Cashmere goat. The estimated value for growth curve parameters of A, B and K were 17.97, 1.97 and 0.017, respectively. The weight and age at point of inflection were 6.63 kg and 52.94 days, respectively. Direct heritability estimates for A, B, K, IA and IW were low values of 0.14, 0.10, 0.03, 0.14 and 0.14, respectively. Low estimated values for direct heritability of the studied growth curve traits in Raeini Cashmere goat indicated that direct selection for these traits may not be useful in terms of achieving genetic change. Direct genetic correlations ranged from -0.76 (K-IW) to 0.98 (A-IW). Phenotypic correlation estimates were generally lower than the direct genetic ones and ranged from -0.30 (K-IW) to 0.69 (A-B and B-IA). IA and IW had high positive phenotypic (0.86) and genetic (0.99) correlations, implying IA and IW were highly correlated in terms of phenotypic and genetic effects. The studied growth curve parameters of Raeini Cashmere goat have shown low levels of additive genetic variation.