Selection for Growth and Feed Efficiency in Broiler: Realized Heritability and Responses of Selection

The trait of body weight at a fixed age under ad libitum feeding is becoming less attractive due to accumulating negative impact of traits correlated t o body weight. The correlation between weight gain and fat deposition is low but positive. The main g oal of this study was to estimate genetic parameter s, realized heritability and responses of selection. D ata consisted of two selection lines in broiler, na mely body weight (BW) and feed conversion ratio (FCR) lines. Estimation of genetic parameter was calculated by ASREML procedures based on animal model. Estimation of heritability was calculated through the regression of phenotypic means on cumulatively differential selection. Responses of selection were estimated by using average breeding value at each generation. Estimated heritability fo r body weight was 0.42 for BW line and 0.59 for FCR line, respectively. Estimated heritability for feed conversion was 0.44. However, there was an inconsistency between estimated and realized heritabilities. All traits measured had small-reali zed heritability, even they were negative for body weight and feed conversion in FCR line. The realize d heritability for body weight in BW line was 0.10, while those for body weight and feed conversi on in FCR line were -0.14 and 0.03. Genetic correlation between body weight and feed conversion ratio was 0.18, whereas phenotypic correlation showed no difference to 0.