Abstract: Using 14 microsatellite loci, we analyzed the genetic variation of eight BWEL-SPF chicken families in F15 generation. The results showed that, due to the inbreeding over 14 generations following mating within families, a number of locus (35.7%, 5/14) had been fixed with single alleles or approaching to fixation with single predominant alleles. The genetic variation in general had been reduced significantly within families. However, the change of mating scheme from within families to between families since the F15 generation could have converted the positive inbreeding FIS values to negative out-breeding FIS estimates in most families (7/8) with four of them significantly deviated from zero (P<0.05), indicating a considerable compromise in inbreeding within the families. Significant tests for the pair-wise FST estimates indicated highly significant genetic differentiations between the eight families (P<0.001). There was 12.9% of the total genetic variation present among the families, implying the presence of significant genetic differentiation once present among the families over 14 generations followed within-family selection and breeding.

Key words: microsatellite DNA marker; SPF chicken; genetic variation