QTL and candidate genes for fecundity in sows

Abstract

Fecundity in pigs is a trait of major economic interest but low heritability. For the improvement of fecundity, genetic markers for selection are desirable and therefore, several searches for genetic variation influencing fecundity have been performed. The aim of this review is to compare and to evaluate all published QTL analyses and candidate gene approaches concerning reproductive traits in sows. For this purpose, we present a comprehensive cytogenetic map comprising 54 QTL and 11 candidate genes with influence on reproductive traits. The evaluation and comparison of the results showed similarities, but also marked differences among studies. Reasons for different results are multicausal and are due to differences between resource populations, number of evaluated animals, mating systems, measured phenotypical traits and environmental influences. We could show that chromosome 8 and to a lower extend chromosome 7 are the most important chromosomes with regard to reproductive traits in pigs. For further research, fine mapping of the identified QTL regions is necessary in order to confirm and to narrow the most likely chromosomal intervals. Although difficult to perform, an advance would be a standardization of the experimental setup in particular, in respect to the collection of phenotypic data. Furthermore, we suggest to publish the information on further identified QTL and candidate genes as comprehensive and accurate as possible in order to allow a more transparent comparison and collation of the results.

Detection of quantitative trait loci for teat number and female reproductive traits in Meishan × Large White F2 pigs

“…The QTL detected on ES do not correspond to the single previously published QTL on prenatal survival (King et al, 2003). Moreover, no reproduction QTL clearly corresponds to the chromosomal regions where reproduction candidate genes have been detected (Buske et al, 2006). Indeed, two potential candidate genes for litter size, i.e.…”

A pilot study on transcriptome data analysis of folliculogenesis in pigs

“…Thus, different types of studies have been undertaken to elucidate and improve the different components of this complex trait. The two main approaches are QTL studies and candidate gene studies (Buske et al, 2006). However, until now, no gene explaining a major effect on reproductive performance has been found in pigs, suggesting that this is a complex phenomenon.…”

ESR1andESR2gene markers are not associated with number of piglets born alive in Italian Large White sows

“…Rothschild et al (1994Rothschild et al ( , 1996 indicated that ESR1 B allele was associated with increased litter size in PIC synthetic lines made with Meishan or Large White blood. However, the effects of this polymorphism on litter size resulted contradictory (Alfonso, 2005;Buske et al, 2006a;Distl, 2007), so it has been largely debated whether the ESR1 locus could or not be introduced into breeding programs.…”

“…The use of DNA-based information (marker assisted selection and gene assisted selection, MAS and GAS, respectively) in conjunction with traditional selection methods could be useful to accelerate genetic progress for litter size and female reproduction efficiency in pigs. Several candidate genes for sow prolificacy have been already evaluated in different pig breeds/lines (Buske et al, 2006a;Spötter and Distl, 2006;Distl, 2007). Among these genes, estrogen receptor 1 (ESR1) and estrogen receptor 2 (ESR2) polymorphisms have been reported to explain part of litter size variability in several pig populations.…”