Selection experiment on body weight for increasing the proportion of standard egg-size in Japanese quail

The purpose of the present experiment was to investigate the effective selection method for increasing the proportion of standard egg-size (9.5-11.5 g egg weight) in Japanese quail. The base populations for this study were mated between two lines that had been maintained in Aichi-ken Agricultural Research Center (males: middle egg weight line, females: large egg weight line). The base population was divided equally into 3 groups according to genetic performance. In each group, this study involved two selected lines: line B was selected on average body weight (160 days of age), whereas line E was selected directly on standard egg-size weight (160 days of age). A non-selected control line (C) served as the base population for these two lines. Females were individually selected, while males were selected on the basis of the performance of females from the same progeny in the both lines. The following conclusions were obtained; After five generations of selection, selection intensity for body weight was close to zero and the uniformity on body weight tended to increase in the B line. Furthermore, there was evidence that the increase in the proportion of standard egg-size was significantly greater (P0.05) in the B line than the E line in generation 5. The pooled heritabilities across generations of selection traits (body weight, egg weight) estimated by sire plus dam component analysis of variance were observed to be very similar to values among the lines. In addition, the heritabilities were estimated as comparatively high values (above 0.4) and high values (above 0.6) for body weight and egg weight, respectively. The genetic and phenotypic correlations between body weight and egg weight were positive in both the lines. Data from this experiment indicates that the selection method for reduced variation of body weight in the population is effective, therefore this method can be expected to be better in increasing proportion of standard egg-size than direct selection on egg weight in Japanese quail.