Heterosis in normal versus dwarf laying hens.

The effect of genotype at the sex-linked dwarf locus on heterosis in crosses between a White Leghorn and a brown egg line for body weight, egg production, and related traits was studied. Heterozygous Dw/dw males were used to produce normal and dwarf pullets in each of the pure lines and their reciprocal crosses (eight genotype-line combinations). There were 54 pullets per combination. Line differences were significant for shank length, body weights at 8, 17, and 52 wk, age at first egg, egg number, clutch length, rate of lay, and egg weight. Heterosis was observed for all of these traits. Body weight as a covariate was not important in analyses of egg number, clutch length, and egg weight. The egg production reduction associated with the dw gene in pure lines was smaller in F1 hens. This discovery may be adequate to warrant use of dwarf crossbred hens for egg production.