Abstract
The objective of this study was to report the response to selection for fertility and hatchability in white egg layers strains, based on sire and dam performance, and the effects of inbreeding on these traits. Two selected white egg strains (CC and DD) from Embrapa´s poultry program under multiple trait selection were compared to a control strain (CCc). The control strain was established by randomly mating one male from each sire family to a non-related female from each dam family and was used to monitor genetic change in the selected lines. CC and DD were selected using family and individual information on hen-day egg production up to 40 weeks of age, egg weight, sexual maturity and 16-week-old body weight over five generations. Independent culling levels (ICL) were also used during population expansion to eliminate sires and dams with low fertility (FERT) and hatchability (HATC). Initially, FERT and HATC were over 90.0% in both selected and control strains. FERT and HATC of the selected and the control strains were compared during the last generation. FERT averages were 93.8, 93.8 and 94.4%, and HATCH averages were 93.2, 91.6 and 93.1% for CC, DD and CCc respectively. FERT and HATCH means were not different among strains. Estimated inbreeding increased at a rate of 0.4% per generation in all strains. Selection using ICL was able to effectively maintain the high initial FERT and HATC levels, and provide potential for high selection intensity in other traits. Inbreeding depression was not observed for any trait, indicating that selection compensated for any negative effects of inbreeding.
Highlights
Poultry breeders must consider so many traits that are economically important that it becomes difficult to apply sufficient selection pressure on the Key traits in egg stocks are egg production rate, sexual maturity, viability, egg size, feed efficiency, fertility and hatchability
The objective of this paper was to report the response to selection for fertility and hatchability, based on sire and dam performance, and the effects of inbreeding on these traits in white egg layer strains under multiple trait selection
The genetic trend of the selected strains was calculated using the deviation from control strain CCc as show in Figures 2A and 2B
Summary
Poultry breeders must consider so many traits that are economically important that it becomes difficult to apply sufficient selection pressure on the Key traits in egg stocks are egg production rate, sexual maturity, viability, egg size, feed efficiency, fertility and hatchability. Others traits such as egg quality and body weight are generally of less importance, unless when a strain exhibits specific problems. Recessive genes with large negative effects and at very low frequency seriously violate index assumptions, and this appeared to be true of fertility and hatchability in the current studies.
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