Effects of the sex-linked dwarfing gene (dw) on growth and reproduction in white Leghorn hens.
The influence of the dwarfing gene, dw, on growth and reproduction was determined by comparing 1) pure line and reciprocal cross dwarf and normal layers and 2) dwarf and normal full-sib sisters. In Experiment 1, two lines of chickens, the Oregon State University randombred dwarf Leghorn population (D) and Shaver Starcross "288" Leghorns (S), were mated within line and reciprocally to produce normal-sized (SS, SD) and dwarf (DS, DD) female progeny. All progeny were reared similarly until 18 weeks of age when birds were transferred to individual cages. At 18 weeks of age, half the pullets were fed a basal laying ration containing 15% protein while the remaining birds received the basal ration with .1% supplemental methionine. In Experiment 2, full-sib normal and dwarf sisters were obtained by mating hemizygous dwarf females to heterozygous males. Layers were reared in a similar manner to those in Experiment 1 with the exception that all layers received the basal ration with .1% methionine supplemented. Methionine supplementation in Experiment 1 significantly increased egg weights at 35 and 62 weeks of age for all lines and crosses but had no effect on other growth and reproductive traits. Genotype X diet interactions were not observed for any of the measured traits. Normal-sized layers had significantly heavier body weights and longer shank lengths than dwarf layers in both experiments. Dwarf hens in both experiments showed reduced egg production capabilities, although ages at sexual maturity were similar among phenotypes. Dwarf layers laid smaller eggs than normal-sized layers. There were no consistent differences in feed efficiency measures between normals and dwarfs.
D000818:Animals; D001835:Body Weight; D002645:Chickens / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D003433:Crosses, Genetic; D005260:Female; D005796:Genes; D006823:Hybrid Vigor; D008297:Male; D008957:Models, Genetic; D012098:Reproduction; D012730:Sex Chromosomes