Independent Effects of K and k+ Alleles and Maternal Origin on Mortality and Performance of Crossbred Chickens

Abstract

Rapid feathering daughters of White Leghorn X Rhode Island Red reciprocal crosses were backcrossed to K/k+ heterozygous White Leghorn males to form four synthetic sublines. Each subline represented a unique combination of slow (K) and rapid (k+) feathering with the heavy or light breed maternal origin of the W sex chromosome. Higher mortality rates in the growing and adult stages of the backcross female progeny were associated with the K genotype but not with k+. However, higher mortality in the adult period was also independently associated with the heavy breed maternal origin. Hen-housed rate of lay, confounded with mortality and sexual maturity, was depressed by K, but hen-day rate was unaffected. Body and egg weights at 40 weeks of age were higher in the maternal line originating from Leghorns than in the line originating from Rhode Island Reds but were unaffected by feathering genotype.