Fine mapping the number of corpora lutea quantitative trait loci on SSC3: Analysis of the porcine follicle‐stimulating hormone receptor gene

In females, follicle‐stimulating hormone (FSH) targets a FSH receptor (FSHR) expressed only on granulose cells, inducing maturation of the ovarian follicles. We hypothesized that genetic variants in the FSHR gene influence litter size by affecting the number of corpora lutea. We fine‐mapped a region of Sus Scrofa chromosome 3 that contains quantitative trait loci for corpora lutea. Polymorphisms were detected in the exons and 5′ flanking region of the porcine FSHR gene, a positional candidate for the statistically most significant of the quantitative trait loci. Finally, 248 F₂ animals from a Duroc and Meishan cross were genotyped for three FSHR SNPs at positions 74, 532 and 1166, and these were correlated with the phenotypes of litter size and corpus luteum number. Three haplotypes were identified: M1 (G/G/C), M2 (C/A/T) and D (C/A/C). In the F₂ population, the M1 haplotype was associated with a greater number of corpora lutea (P < 0.01) and also seemed to be associated with increased litter size, although the association was not significant (P = 0.2571). Some polymorphisms resulting in amino acid substitutions in these genes were excluded from the polymorphisms possibly responsible for the number of corpora lutea.     

A genome scan for quantitative trait loci affecting the length of small intestine in a White Duroc × Chinese Erhualian intercross resource population

The small intestine is a vital organ in animal gastrointestinal system, in which a large variety of nutrients are absorbed. To identify quantitative trait loci (QTL) for the length of porcine small intestine, phenotypic values were measured in 1034 individuals at 240 d from a White Duroc × Chinese Erhualian intercross F₂ population. The length of small intestine showed strong correlation with growth traits and carcass length in the F2 population. A whole‐genome scan was performed based on 183 microsatellites covering the pig genome in the F₂ population. A total of 10 QTL for this trait were identified on 8 pig chromosomes (SSC), including four 1% genome‐wide significant QTL on SSC2, 4, 7 and 8, one 5% genome‐wide significant QTL on SSC12, and five 5% chromosome‐wide significant QTL on SSC5, 7, 13 and 14. The Erhualian alleles were generally associated with shorter length of the small intestine except the alleles on SSC7 and 13. The QTL on SSC4 overlapped with the previously reported QTL for the length of small intestine. Several significant QTL on SSC2, 8, and 12 were consistent with previous reports. The significant QTL detected on SSC7 was reported for the first time. All QTL identified in this study corresponded to the known region significantly associated with growth traits, supporting the important role of the length of small intestine in pig growth.