A study of heterosis and recombination loss in crosses of inbred Leghorn lines derived from a common base population.

This study was designed to estimate heterosis and recombination loss of feed efficiency at peak egg production using six inbred White Leghorn lines and their crosses. Percent hen day egg production was highest in three-line crosses with 94.6%, 93.5% for two-line crosses and 91.0% for inbred lines, respectively. Feed efficiency of three-line crosses was superior to that of two-line crosses, primarily because of low feed consumption. Heterosis effects for body and egg weights were observed in all mating combinations. The value of heterosis for egg number and feed efficiency were dependent upon parental line. Egg number and egg weight showed small average recombination losses, depending on lines involved. Small but consistent recombination loss for body weight was observed. The recombination loss for feed efficiency was large and negative; the highest three-line cross value for this trait was about 16% above that of the mean of the corresponding two-line crosses.