Genetic markers for persistency and egg shell quality during an extended laying period.

Egg production represents a major agricultural activity in Canada with a production of over 588 million dozen eggs, for a farm gate value of over $733 million, in 2006. Moreover, it is estimated that the sector employs roughly 11,000 persons and, when accessory activities are taken into account, contributes in excess of $1.5 billion to the Canadian economy. Traditional selective breeding has transformed the modern commercial laying hen into a remarkably efficient producer of eggs, with average annual production rates in excess of 300 eggs per bird. As flocks age, however, egg production is reduced through mortality, an overall decline in fertility, and egg quality deficiencies. Increased persistency (the duration of the high quality egg production period) in layers could improve profit in the layer industry through savings in replacement costs. Although persistency has been a selection objective for some time, progress in this area has been slow and costly. This is due to a number of factors including the late expression of the trait and its limited heritability. The use of DNA markers can accelerate genetic progress, especially in traits such as persistency which are difficult to improve by traditional means. Currently, DNA markers for persistency in chickens are not available. The objective for this study is the development of such markers through the validation in layer hens of a series of candidate genes for fertility and reproductive lifespan. Once validated, these markers can be used by the layer industry to accelerate genetic progress towards the selection of elite lines with extended persistency and improved late stage egg quality.