Empirical Bayes factor analyses of quantitative trait loci for gestation length in Iberian × Meishan F2 sows

Abstract

The aim of this study was to investigate chromosomal regions affecting gestation length in sows. An experimental F 2 cross between Iberian and Meishan pig breeds was used for this purpose and we genotyped 119 markers covering the 18 porcine autosomal chromosomes. Within this context, we have developed a new empirical Bayes factor (BF) approach to compare between nested models, with and without the quantitative trait loci (QTL) effect, and after including the location of the QTL as an unknown parameter in the model. This empirical BF can be easily calculated from the output of a Markov chain Monte Carlo sampling by averaging conditional densities at the null QTL effects. Linkage analyses were performed in each chromosome using an animal model to account for infinitesimal genetic effects. Initially, three QTL were detected at chromosomes 6, 8 and 11 although, after correcting for multiple testing, only the additive QTL located in cM 110 of chromosome 8 remained. For this QTL, the allelic effect of substitution of the Iberian allele increased gestation length in 0.521 days, with a highest posterior density region at 95% ranged between 0.121 and 0.972 days. Although future studies are necessary to confirm if detected QTL is relevant and segregating in commercial pig populations, a hot-spot on the genetic regulation of gestation length in pigs seems to be located in chromosome 8.

A whole genome scan to detect quantitative trait loci for gestation length and sow maternal ability related traits in a White Duroc × Erhualian F2 resource population

“…The value was comparable with the mean gestation length in a naturally mated West-type population (113.5 to 114.5 days) (Leenhouwers et al, 1999;Cassady et al, 2002), but longer than in Iberian 3 Meishan F 2 sows (112.16 days), which were mated with artificial insemination (Casellas et al, 2008). Just as the results reported by Sasaki and Koketsu (2007), gestation length had a negative correlation with total number of born piglets.…”

“…According to the human-pig comparative maps, except the Booroola fecundity gene (BMPR1B) which was related with gilt prolificacy at first parturition (Tomas et al, 2006), there are no other genes associated with animal reproduction near the QTL region. The QTL for gestation length on SSC1, 6, 9, 11 and 15 (Wilkie et al, 1999;Casellas et al, 2008) were not observed in this study. This could be explained by different breeds or genetic background of founder animals in tested F 2 resource populations.…”

“…In this region Jiang et al (2002) found that estrogen sulfotransferase gene showed overdominance effects on gestation length. The peak near the 110 cM was overlapped with QTL region for gestation length reported by Casellas et al (2008) in the Iberian 3 Meishan F 2 sows, although it did not achieve s.e.…”

“…Wilkie et al (1999) detected three QTL on pig chromosomes (SSC)1, 9 and 15 for gestation length in a three-generation Meishan 3 Yorkshire resource population. Casellas et al (2008) identified three QTL for gestation length on SSC6, 8 and 11 in the Iberian 3 Meishan F 2 sows. Moreover, Jiang et al (2002) found a QTL for gestation length on SSC8 using a candidate gene approach in a Meishan 3 large white resource population.…”

“…The heritability of gestation length in pigs ranges from 0.47 (Leigh, 1981;Hanenberg et al, 2001) to 0.13 (Casellas et al, 2008). The moderate-to-high values of heritability estimated have increased its importance as a potential breeding goal to improve the reproduction efficiency of sow per year (Casellas et al, 2008).…”