The genetic parameters associated with egg production and related traits in a sex-linked dwarf strain of single comb White Leghorns (Gallus domesticus)

Graduation date: 1981The records of a population of sex-linked dwarf layers\ud at the Oregon State Agricultural Experiment Station subjected\ud to an accelerated selection for hen-housed egg production at\ud 40 weeks of age for a period of over 11 years were analyzed\ud for selection response, and for the estimation of genetic\ud parameters. The parameters obtained from the study were used\ud to derive selection indexes that might maximize genetic-economic\ud gains in egg production and related traits.\ud The response to selection for increased egg production\ud was positive. The basic trait, hen-housed egg production at\ud 40 weeks, increased significantlv from an average of 24 eggs\ud per bird in 1966 to 108 eggs in 1976. Residual egg production,\ud or net rate of lay, increased from 27 to 109 eggs. The\ud total hen-housed egg production at 68 weeks of age increased,\ud as a correlated response, from 51 to 218 eggs. Sexual maturity\ud improved also as a correlated response to selection on\ud the basis of part-year egg number to a fixed, date. Age at\ud first egg declined from 32 weeks to 21.7 weeks. In the last\ud generation egg production was comparable to or slightly\ud better than that in some of the commercial control samples.\ud The early egg weight improved by 3.0 grams when the last\ud population was compared to the initial unselected one.\ud The heritability estimates for egg production index,\ud sexual maturity, and 10 week body weight, all based on the\ud pooled dam component of variance, were higher than the estimates\ud based on the sire components, but the heritability estimates\ud for egg weight were lower.\ud The genetic correlations between body weight, and egg\ud weight measures were positive. The genetic correlations\ud between egg number and egg size measures were negative. The\ud heritability and correlation estimates in the dwarf strain\ud were generally all comparable to those reported in the literature\ud for normal size strains