Egg white polymorphisms and economic characters in the domestic fowl

Synopsis

The possible association between genes at 4 egg white loci, Ov, II, III, and Tf and 4 production characters were studied in 3 closed populations consisting of 2 flocks of White Leghorns, each of about 1000 hens, and a Light Sussex flock of 380 hens. The characters studied were: body weight at 5 different ages, egg weight at 3 different ages, age at sexual maturity and egg number at 2 ages. Only the last two characters were studied in the Light Sussex population. Three egg white loci had statistically significant effects on production traits. With body weight and egg weight, the Ov locus had an additive effect, the Ov^A allele being superior. The influence on body weight was significant only on adults, i.e., post‐sexual maturity weights. This was shown to be partly attributable to differences in age at maturity. Locus II was significantly overdominant with respect to egg number in 2 populations while the Tf locus heterozygotes were significantly inferior to the Tf^b/Tf^b homozygotes in the Light Sussex flock. In addition to these direct effects, complex interactions involving these loci were also present on egg number. The additive genetic variance controlled by these loci was also determined. The proportion of the variance attributable to these loci (as a fraction of the additive genetic variance of the trait) was not large enough for any single trait to be of practical importance in selection.

Notes

Present address: Central Poultry Research Station, Kundasale, Ceylon.