Response to selection for feed conversion ratio in Japanese quail

We investigated the effect of selection for 4-wk feed conversion ratio (FCR) on genetic improvement of FCR, BW, weight gain (WG), feed intake (FI), and residual FI (RFI) in Japanese quail. The F line was selected for reduced FCR and the C line was maintained as a randombred control. In each generation, 35 sires and 70 dams were used as parents for the next generation. Three generations of selection were performed. Realized heritability for FCR was calculated as the ratio of cumulative selection response to the cumulative selection differential, and additionally, genetic response was quantified as the difference between the means of selection and control lines. The results showed that realized heritability for FCR after 3 generations of selection was 0.67. The mean FCR in F line and C line in the last generation was 2.13 and 2.61, respectively. This is 18.4% cumulative genetic improvement, or 6.1% improvement per generation. In the last generation, the means of F and C lines were 193 and 166 g for BW at age 28 d (16.4% total increase, or 5.5% per generation), 184 and 158 g for WG (17.2% total higher gain and 5.7% per generation), 393 and 413 g for FI (4.9% total higher consumption and 1.6% per generation), and -24.5 and 10.2 for RFI (-34.7 g of cumulative gain; -11.6 g per generation), respectively. These results show that selection to decrease FCR increases BW and WG and decreases FI and RFI as a correlated response.