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Abstract
Three quail lines were used in the present experiment which carried out at the Poultry Research Center in Demo, Faculty of Agriculture, Fayoum, to study the effect of divergent selection for shank length (SL) in Japanese quail and assaying the polymorphism of the PIT1 gene, line established for selection for long SL at 28 days of age (LSL28), line established for selection for short SL at 28 days of age (SSL28) and random bred control line (RBC). The experiment continued for three generations after establishing the base population. The results obtained can be summarized as follows: The SL28 in the base population had a relatively higher heritability, phenotypic and genetic correlations in a desired direction with some productive performance traits. Therefore, this trait was used as selection criteria to improve these target productive performance traits indirectly, especially those having lower h2’s than SL trait. The genetic and phenotypic responses to divergent selection showed that the LSL28 line was significantly longer SL than the SSL28 line in all generations. The LSL28 line showed higher phenotypic direct responses by generation than the SSL28 line for each of females, males and combined sexes, respectively. Both the selected lines showed a marked change in SL28 indicating significant genetic improvement.
In conclusion, selection for SL28 was effective in its genetic improvement with a high degree of correspondence between the expected and realized genetic changes. A significant asymmetrical response due to selection between the two divergent lines was found favoring the LSL28 line. Significant desirable correlated responses were evident for body weight and most of egg production related-traits. Natural selection did not appear to counteract artificial selection. Lack of changes in heritabilities over generations implied the existence of significant genetic variability in the populations to warrant continued response to selection for SL28.