Abstract
Variation in sexual dimorphism (SD) is particularly
marked in meat-type chickens. This paper investigates
the genetic basis of SD in an important economic trait, i.e.
body weight (BW) at 35 days of age, in broilers by applying
quantitative genetic analysis. A large dataset comprising
203,323 BW records of a commercial line of broiler chicken
was used. First, a bivariate approach was employed treating
BW as a sex-specific trait. During this approach, seven
bivariate models were applied and variances due to direct
additive genetic, maternal genetic and maternal environmental
effects were estimated via the restricted maximum
likelihood method. The best-fitting model included direct
additive genetic, maternal genetic and maternal environmental
effects with a direct–maternal genetic covariance.
Differences between male and female direct heritabilities
were non-significant (0.28 vs. 0.29 for males and females,
respectively), implying no need for sex-specific selection
strategies. The direct–maternal genetic correlation was more
strongly negative in males than in females (−0.72 vs. −0.56),
implying a more profound antagonism between direct additive
and maternal genetic effects in this particular gender.
The direct genetic correlation of BW between the two sexes
was as high as 0.91, i.e. only slightly lower than unity. Second,
variance components and genetic parameters of two measures
of SD, i.e. the weight difference (Δ) and the weight ratio (R),
between the genders were estimated. Direct heritabilities for
both measures were significantly different to 0 but of low
magnitude (0.04). Apart from the additive–maternal covariance,
no other random effects were found to be of importance
for Δ and R. The results of the present study suggest that only
minimal selection responses due to the selection ofΔand/or R
and a small capacity for amplifying or reducing the BW
differences between the sexes are to be expected in this
specific population. Furthermore, selection pressure on BW
is expected to amplify SD.
Original language | English |
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Pages (from-to) | 61 - 70 |
Number of pages | 10 |
Journal | Journal of Applied Genetics |
Volume | 54 |
Issue number | 1 |
DOIs | |
Publication status | Print publication - Feb 2013 |
Externally published | Yes |
Bibliographical note
1023517Keywords
- Direct-maternal genetic correlation
- Maternal effects
- Sexual dimorphism