Abstract
To improve feed efficiency highly associated with net economy in layer chickin, a selection experiment for three generations in a closed flock of Rhode Island Reds was conducted by use of an index consisting of part records of egg mass, feed intake and body weight. The index was calculated on the basis of estimated parameters in the initial generation and the same index was used throughout the three generations.
Results of the selection were summarized in Table 7. The net economic value was improved by 162% for the period (up to 273 days of age) in which the part records were taken and 155% for the whole year period (up to 469 days of age).
All traits were improved towards the intended directions, although the ratios of realized to expected genetic gain varied substaintially among traits measured. Parts of such discrepancies between expected and realized gain in various traits could be ascribed to the bies of estimated population parameters such as heritabilities and genetic correlations.
