Abstract
BackgroundThe fertility of a chicken's egg is a trait which depends on both the hen that lays the egg and on her mate. It is also known that fertility of an individual changes over the laying period.MethodsLongitudinal models including both random genetic and permanent environmental effects of both the female and her male mate were used to model the proportion of fertile eggs in a pedigree broiler population over the ages 29-54 weeks.ResultsBoth the male and the female contribute to variation in fertility. Estimates of heritability of weekly records were typically 7% for female and 10% for male contributions to fertility. Repeatability estimates ranged from 24 to 33%, respectively. The estimated genetic variance remained almost constant for both sexes over the laying period and the genetic correlations between different ages were close to 1.0. The permanent environment components increased substantially towards the end of the analyzed period, and correlations between permanent environment effects at different ages declined with increasing age difference The heritability of mean fertility over the whole laying period was estimated at 13% for females and 17% for males. A small positive correlation between genetic effects for male and female fertility was found.ConclusionOpportunities to improve fertility in broiler stocks by selection on both sexes exist and should have an impact throughout the laying period.
Highlights
The fertility of a chicken's egg is a trait which depends on both the hen that lays the egg and on her mate
The weekly proportion of fertile eggs was modelled as a trait of the hen which laid the eggs and of her mate, with both birds contributing genetic effects and nongenetic individual specific effects
The increase in likelihood was small when the male and female genetic effects were modelled with a linear regression on weeks rather than a constant for each (Table 1) with almost all the increase due to females
Summary
The fertility of a chicken's egg is a trait which depends on both the hen that lays the egg and on her mate. It is known that fertility of an individual changes over the laying period. As there is a negative correlation between growth and fertility, especially in naturally mated flocks [1], selection for growth alone over several generations is likely to result in a decline in fertility or in the ability of the males to mate efficiently [2,3]. Fertility of an individual egg is a function of the genotype of the embryo, to which both parents contribute. Both paternal and maternal components should be accounted for simultaneously when analyzing fertility
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