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We performed a whole genome QTL analysis to confirm the existence of QTL affecting fatty acid composition and to investigate the effects of additive, dominance, imprinting, and epistatic interactions between QTL in an [F.sub.2] resource population. The [F.sub.2] population, comprising 166 pigs, was obtained by crossing a Duroc boar and a Meishan sow. The [F.sub.2] population was measured for fatty acid composition and was used for whole genome QTL analysis, using a total of 180 microsatellite markers. The suggestive and significant thresholds were equivalent to likelihood ratio test statistics (LRT) of 13.7 and 20.5, respectively. For single QTL analysis, 2 suggestive QTL and 1 significant QTL were detected. Suggestive QTL for C14:0 and C16:1 were identified on chromosomes 12 and 7, respectively, and a significant QTL for C18:2 was detected on chromosome 5 with the greatest LRT of 22.9. For C14:0, a significant QTL with paternal imprinting effect was also detected on chromosome 12, where the locus was in the same region as an additive QTL effect, with a large LRT of 24.2. The suggestive QTL on chromosome 7 was not significant when correction for backfat thickness was included. For epistatic QTL analysis, a total of 5 epistatic pairs were located on chromosomes 4, 5, 9, and 16. The same epistatic pairs were significant when correction for backfat thickness was included. The individual QTL identified in the single QTL analysis and in the epistatic QTL analysis were not the same loci, except for C18:2. For C14:0, an epistatic QTL pair was detected on chromosome 16, with the least P-value of 4.9 x [10.sup.-12]. The present study constitutes one of the first reports on the mapping of imprinted QTL and epistatic pairs of QTL affecting fatty acid composition in a swine population. Key words: epistatic interaction, fatty acid composition, quantitative trait locus, swine doi: 10.2527/jas.2009-1917

Many QTL analyses related to meat production and meat quality traits have been carried out using an [F.sub.2] resource population produced by crossing 2 genetically different breeds. This experiment was intended to investigate whether these QTL were segregating in a purebred Duroc population that had been selected for meat production and meat quality traits during 7 generations. Sus scrofa chromosome 7, for which significant QTL of intramuscular fat and many other traits have already been reported, was studied. The polymorphism of 10 microsatellite markers that were arranged at about 20-cM intervals was investigated on 1,004 pigs. In the selected population, 954 progeny were produced from mating of 99 sires and 286 dams. The QTL analysis for a full-sib family population was examined with the multigeneration pedigree structure of the population. Variance component analysis was used to detect QTL in this population and was examined for the multigeneration pedigree population. In this study, multigenerational pedigree estimated identical by descent coefficients among sibs were produced using Markov chain Monte Carlo methods. The maximum likelihood of odds score was found at the 70-cM position for the LM area, at the 0-cM position for the pork color standard, and at the 120-cM position for the number of thoracic vertebra, but no significant QTL for intramuscular fat were detected on SSC 7. These results indicate that QTL analysis via a variance component method within a purebred population was effective to determine that QTL were segregating in a population of purebred Durocs. Key words: Duroc pig, meat quality, multiple generation, quantitative trait loci, selected population

• The study focuses on bull fertility including conception rate and semen traits. • The genetic parameters for bull fertility were estimated in Japanese Black bulls. • Heritability of the bull conception rate was low. • The genetic correlation between bull conception rate and semen motility was high. • Genetic selection for sperm motility could lead to improve bull conception rate. The P of achieving pregnancy is an important trait of bull fertility in beef cattle and is defined as the bull conception rate (BCR). This study aimed to clarify and better understand the genetic architecture of the BCR calculated using artificial insemination and pregnancy diagnosis records from a progeny testing program in Japanese Black bulls. In this study, we estimated the genetic parameters of the BCR and their correlation with semen production traits. In addition, we assessed the correlated responses in BCR by considering the selection of semen production traits. Nine hundred and sixteen Japanese Black bulls were selected based on fertility, with 28 869 pregnancy diagnostic records from the progeny testing program. Our results showed that the heritability estimate was 0.04 in the BCR at the first service and 0.14 in BCR for the three services, and an increase in the inbreeding coefficient led to a significant decrease in BCR. The phenotypic trend of BCR remained almost constant over the years, whereas the genetic trend increased. In addition, the changes in the progeny testing year effect showed a similar tendency to the phenotypic trends, suggesting that the phenotypic trends could be mainly due to non-genetic effects, including progeny testing year effects. The estimated genetic correlation of BCR with sperm motility traits was favorably moderate to high (ranging from 0.49 to 0.97), and those with sperm quantity traits such as semen volume were favorably low to moderate (ranging from 0.23 to 0.51). In addition, the correlated responses in BCR at the first service by selection for sperm motility traits resulted in a higher genetic gain than direct selection. This study provides new insights into the genetic factors affecting BCR and the possibility of implementing genetic selection to improve BCR by selecting sperm motility traits in Japanese Black bulls. [ABSTRACT FROM AUTHOR]