A. Veenendaal

Whole genome scan for quantitative trait loci affecting body weight in chickens using a three generation design

Abstract An experimental population containing 10 full sib families of a cross between two broiler lines was created. In this population blood samples from 20 full sib animals in generation 1 and 451 full sib animals in generation 2 were used for marker genotyping. Data on body weight at slaughter age (48 days) collected in a feed conversion experiment with 2049 individually housed grandoffspring was analysed. Large differences in mean and variance between male and female body weight were found. To account for these differences, a bivariate analysis treating body weight of males and females as separate traits was used to estimate (co)variance components and breeding values. The model accounted for systematic environmental effects and maternal effects. The estimated heritability of body weight was 0.28 in the males and 0.33 in the females and the genetic correlation between male and female body weight did not significantly deviate from unity. Estimated breeding values, fixed and maternal genetic effects were used to calculate average adjusted progeny trait values for all generation 2 animals adjusted for fixed and maternal genetic effects and for the additive genetic contribution of the other parent. Male and female progeny trait values were combined in one trait value adjusting for sex differences by standardisation for mean and variance. This average adjusted progeny trait value was used for QTL detection. To study presence of QTLs, an across family weighted regression interval mapping approach was used both in half sib as well as a full sib QTL analysis. Genotypes from 368 markers mapped on 24 autosomal linkage groups were available. The most likely position for a QTL affecting body weight was found on chromosome 1 at 240 cM with a test statistic of 2.32. Significance levels were obtained using the permutation test. The chromosomewise significance level of this QTL was 10%, whereas the genomewise significance level was 41%. New aspects of this study are: Genomewide QTL analysis in poultry, full sib analysis in an outbred population structure and correction for heterogeneous variances between sexes.

QTL Mapping in chicken using a three generation full sib family structure of an extreme broiler X broiler cross

Abstract A three generation population has been created for mapping both production and health traits in chicken. The Fl and F2 population were genotyped while phenotypes were collected on the F3 animals. The population consisted of 10 full‐sib families with a total of 476 individuals (Fl and F2), and an F3 generation consisting of over 18,000 animals. In total, 264 microsatellites were analyzed on all Fl and F2 animals, and an additional 120 microsatellites were analyzed on only 4 of the 10 families (196 animals). A linkage map of the chicken genome containing 384 microsatellite markers has been constructed by analyzing the segregation of these markers in this population. Preliminary analysis indicate a QTL for body weight at 48 days on chromosome 1. Body weight was measured on 2100 F3 animals housed in cages, and the data was analyzed by a regression interval mapping approach. Higher F‐values were obtained by using a bivariate approach showing that differences in mean and variance of a trait measured on...