The genetic correlation between scapula shape and shoulder lesions in sows.

Shoulder lesions and body condition of sows at weaning have both environmental and genetic causes. The traits can be scored at farm level, and following recording, the traits can be included in the breeding goal and directional selection can be applied. However, to further increase the genetic progress of these traits, it is advantageous to develop indicator traits on the selection candidates (test boars or gilts, not yet exhibiting the phenotype themselves). It has previously been suggested that the scapula morphology and the spine of scapula might be a key factor for the sow to develop shoulder lesions. In this study, we developed 11 novel traits describing the morphology of the shoulder blade based on computed tomography images from scanned test boars. These traits include the area, length, width, height, and volume of the shoulder blade as well as 6 traits obtained from principal component analysis, describing 80% of the variation observed for the scapula spine profile. The analyzed traits have moderate to high heritability (h2 from 0.29 to 0.78, SE = 0.06), low to medium genetic correlations with shoulder lesions (up to 0.4, SE = 0.1), and body condition scoring at weaning (up to 0.25, SE = 0.1). These novel phenotypes can now be recorded automatically and accurately prior to selection of the AI boars. If such recordings are included in multivariate genomic selection models, it is expected to improve the genetic progress of shoulder lesions and body condition score by weaning.

Exploiting whole genome sequence data to fine map and characterize candidate genes within a quantitative trait loci region affecting androstenone on porcine chromosome 5.

Male piglets are routinely castrated to eliminate boar taint. However, this treatment is undesirable, and alternative approaches, including genetic strategies to reduce boar taint, are demanded. Androstenone is one of the causative agents of boar taint, and a QTL region affecting this pheromone has previously been reported on SSC5: 22.6-24.8 Mb in Duroc. The QTL region is one of the few reported for androstenone that does not simultaneously affect levels of other sex steroids. The main objective of this study was to fine map this QTL. Whole genome sequence data from 23 Norwegian Duroc boars were analyzed to detect new polymorphisms within the QTL region. A subset of 161 SNPs was genotyped in 834 Duroc sires and analyzed for association with androstenone in adipose tissue and testosterone, estrone sulphate and 17ß-estradiol in blood plasma. Our results revealed 100 SNPs significantly associated with androstenone levels in fat (P < 0.001) with 94 of the SNPs being in strong linkage disequilibrium in the region 23.03-24.27 Mb. This haplotype block contains at least four positional candidate genes (HSD17B6, SDR9C7, RDH16 and STAT6) involved in androstenone biosynthesis. No significant associations were found between any of the SNPs and levels of testosterone and estrogens, confirming previous findings. The amount of phenotypic variance explained by single SNPs within the haplotype block was as high as 5.4%. As the SNPs in this region significantly affect levels of androstenone without affecting levels of other sex steroids, they are especially interesting as genetic markers for selection against boar taint.

Using markers with large effect in genetic and genomic predictions.

The first attempts of applying marker-assisted selection (MAS) in animal breeding were not very successful because the identification of markers closely linked to QTL using low-density microsatellite panels was difficult. More recently, the use of high-density SNP panels in genome-wide association studies (GWAS) have increased the power and precision of identifying markers linked to QTL, which offer new possibilities for MAS. However, when GWAS started to be performed, the focus of many breeders had already shifted from the use of MAS to the application of genomic selection (using all available markers without any preselection of markers linked to QTL). In this study, we aimed to evaluate the prediction accuracy of a MAS approach that accounts for GWAS findings in the prediction models by including the most significant SNP from GWAS as a fixed effect in the marker-assisted BLUP (MA-BLUP) and marker-assisted genomic BLUP (MA-GBLUP) prediction models. A second aim was to compare the prediction accuracies from the marker-assisted models with those obtained from a Bayesian variable selection (BVS) model. To compare the prediction accuracies of traditional BLUP, MA-BLUP, genomic BLUP (GBLUP), MA-GBLUP, and BVS, we applied these models to the trait "number of teats" in 4 distinct pig populations, for validation of the results. The most significant SNP in each population was located at approximately 103.50 Mb on chromosome 7. Applying MAS by accounting for the most significant SNP in the prediction models resulted in improved prediction accuracy for number of teats in all evaluated populations compared with BLUP and GBLUP. Using MA-BLUP instead of BLUP, the increase in prediction accuracy ranged from 0.021 to 0.124, whereas using MA-GBLUP instead of GBLUP, the increase in prediction accuracy ranged from 0.003 to 0.043. The BVS model resulted in similar or higher prediction accuracies than MA-GBLUP. For the trait number of teats, BLUP resulted in the lowest prediction accuracies whereas the highest were observed when applying MA-GBLUP or BVS. In the same data set, MA-BLUP can yield similar or superior accuracies compared with GBLUP. The superiority of MA-GBLUP over traditional GBLUP is more pronounced when training populations are smaller and when relationships between training and validation populations are smaller. Marker-assisted GBLUP did not outperform BVS but does have implementation advantages in large-scale evaluations.

Genetic parameters of in vivo primal cuts and body composition (PigAtlas) in pigs measured by computed tomography (CT).

Genetic parameters of in vivo primal cuts in breeding pigs using computed tomography were estimated. A total of 2,439 Duroc and 1998 Landrace boars from the Topigs Norsvin boar testing station in Norway were CT scanned as part of the genetic program. In vivo primal cuts were derived from the CT images using atlas segmentation; the method called the Pig Atlas. The (co)variance estimates were obtained from univariate (heritabilities) and multivariate (correlations) animal genetic models using DMU software. The heritabilities for all primal cuts proportions (%) were intermediate to large for both breeds, h2 ranging from 0.15 to 0.50. Negative genetic correlations were found between most of the other primal cuts, and the strongest correlation was between belly and ham. Carcass lean meat percentage showed a positive correlation to shoulder and ham, but was negatively correlated to belly. In this study, in vivo primal cuts from atlas segmentation are used for genetic parameter calculations for the first time. Computed Tomography (CT) makes it possible to measure in vivo body or carcass composition. This will aid the selection response by measuring on the candidates themselves instead of using relatives. Primal cut proportion and composition measured in vivo by computed tomography and atlas segmentation show heritable variation comparable to previous post mortem studies.

Including crossbred pigs in the genomic relationship matrix through utilization of both linkage disequilibrium and linkage analysis.

In pig breeding, the final product is a crossbred (CB) animal, while selection is performed at the purebred (PB) level using mainly PB data. However, incorporating CB data in genetic evaluations is expected to result in greater genetic progress at the CB level. Currently, there is no optimal way to include CB genotypes into the genomic relationship matrix. This is because, in single-step genomic BLUP, which is the most commonly used method, genomic and pedigree relationships must refer to the same base. This may not be the case when several breeds and CB are included. An alternative to overcome this issue may be to use a genomic relationship matrix (G matrix) that accounts for both linkage disequilibrium (LD) and linkage analysis (LA), called G. The objectives of this study were to further develop the G matrix approach to utilize both PB and CB genotypes simultaneously, to investigate its performance, and the general added value of including CB genotypes in genomic evaluations. Data were available on Dutch Landrace, Large White, and the F1 cross of those breeds. In total, 7 different G matrix compositions (PB alone, PB together, each PB with the CB, all genotypes across breeds, and G) were tested on 3 maternal traits: total number born (TNB), live born (LB), and gestation length (GL). Results show that G gave the greatest prediction accuracy of all the relationship matrices tested for PB prediction, but not for CB prediction. Including CB genotypes in general increased prediction accuracy for all breeds. However, in some cases, these increases in prediction accuracy were not significant (at < 0.05). To conclude, CB genotypes increased prediction accuracy for some of the traits and breeds, but not for all. The G matrix had significantly greater prediction accuracy in PB than the other G matrix with both PB and CB genotypes, except in one case. While for CB, the G matrix with genotypes across all breeds gave the greatest accuracy, though this was not significantly different from G. Computation time was high for G, and research will be needed to reduce its computational costs to make it feasible for use in routine evaluations. The main conclusion is that inclusion of CB genotypes is beneficial for both PB and CB animals.

The effect of including genomic relationships in the estimation of genetic parameters of functional traits in pigs.

The term functionality in animal breeding is used for traits that increase the efficiency of production by lowering the input cost, such as animal health and leg weakness related to longevity. The main objective of the study was to investigate the impact of genomic information, in a multivariate variance component analysis, on some of these traits. In addition, the effect of the inclusion was studied by testing the model's prediction ability based on best linear unbiased estimates for fixed and random effects. The material in this study consists of phenotypes from 76,683 animals, of which 4933 animals are genotyped. The heritabilities for front leg conformation, stayability, osteochondrosis and arched back, estimated using the traditional pedigree, were found to be between 0.12 and 0.29. When using the combined genomic and pedigree relationship matrix, the heritabilities were between 0.14 and 0.36. The results show that the combined relationship matrix can be used for the estimation of (co)variance components, and that the predictive ability of the model in this study marginally increases with the inclusion of genomic information.

Genetic trends of conformation traits and genetic correlations to osteochondrosis in boars.

The objective of our study was to investigate the heritabilities and genetic correlations between traits from a linear exterior assessment system and osteochondrosis (OC) measured by computed tomography (CT), and in addition, to study the genetic trend in a population where the conformation traits have been included in the breeding goal. The data material consisted of phenotypes from a total of 4571 Norsvin Landrace test boars. At the end of the test period, all boars were subjected to a detailed exterior assessment system. Within 10 days of the assessment, the boars were CT scanned for measuring OC. The total score of osteochondrosis (OCT), used in this study, is the sum of phenotypes from the assessment on the medial and lateral condyles at the distal end of both the humerus and the femur of the right and the left leg of the boar based on images from CT. The exterior assessment traits included in the study were; 'front leg knee' (FKNE), 'front leg pasterns' (FPAS), 'front leg stance' (FSTA), 'front leg twisted pasterns' (FFLK), 'hind leg stance', 'hind leg pasterns' (HPAS), 'hind leg standing under' (HSTU), 'hind leg small inner toe', 'dipped back', 'arched back' (ARCH) and 'waddling hindquarters' (WADL). The estimation of (co)variance components and breeding values were performed using bivariate animal genetic models. Breeding values for HSTU, HPAS, FPAS, WADL and OCT traits were additional outputs from the same bivariate analyses. The lowest heritability was found for FFLK (h 2 FFLK=0.05), whereas FPAS was estimated to have the highest heritability (h 2 FPAS=0.36), and OCT demonstrating a heritability of 0.29. Significant genetic correlations were found between several traits; the strongest correlation was between FSTA and FFLK (0.94), which was followed by the correlation between FPAS and FKNE (0.69). The traits ARCH and FSTA had significant genetic correlations to OCT, whereas all other genetic correlations between OCT and the conformation traits were low and not significantly different from 0. Our study shows positive genetic trends for the conformation traits included in the breeding goal. In general, low genetic correlations between conformation traits and OC were observed in our study.

Molecular characterization of the porcine TEAD3 (TEF-5) gene: examination of a promoter mutation as the causal mutation of a quantitative trait loci affecting the androstenone level in boar fat.

A quantitative trait loci (QTL) for accumulation of androstenone in fat has been identified in an Large White × Meishan cross in a region of SSC7-containing TEAD3. In humans, TEAD3 is a transcription activator, known to be able to regulate the transcription of HSD3B. This enzyme is involved in the degradation of androstenone in the liver. In this study, porcine transcripts of TEAD3 were characterized and compared with mammalian transcripts. The complete structure of porcine TEAD3 gene was characterized including two 5' non-coding exons and one exon 5 not used in porcine transcripts. Variations were screened in sequences related to TEAD3: in exons, in flanking sequences of exons and in the promoter region. A SNP characterized at 726 bp at 5' of the first exon was tested on several pig populations without coherent and convincing results concerning its association with androstenone levels. We showed that in the liver of adult boars, the transcripts levels of TEAD3 and HSD3B were correlated. As in humans, it is possible that HSD3B is a target gene of TEAD3 in porcine liver. Nevertheless, no expression variation was observed for TEAD3 or HSD3B in liver between animals with different genotypes at the SNP. We concluded that this SNP was not the causal mutation of this QTL.

Expression levels of 25 genes in liver and testis located in a QTL region for androstenone on SSC7q1.2.

A quantitative trait locus (QTL) for boar fat androstenone levels has been identified near the SSC7 centromere in a Large White × Meishan cross. Backcrosses were produced to isolate the Chinese haplotype in a European genetic background. The expression of 25 genes from the QTL region was studied in the testes and livers of 5-month-old backcross boars, with the aim of identifying the causal gene. Using Fluidigm, a new high-throughput technology, the expression of 25 genes was measured in a single real-time PCR experiment. This study found six significantly down-regulated genes (C6ORF106, C6ORF81, CLPS, SLC26A8, SRPK1 and MAPK14) in the testes of MS-LW backcross boars. However, according to current knowledge, none of the genes appear to be related to androstenone metabolism. In the livers, none of the genes were significantly up- or down-regulated, including TEAD3, which was previously designated as a possible candidate to explain this QTL.

Revealing genetic relationships between compounds affecting boar taint and reproduction in pigs.

Boar taint is characterized by an unpleasant taste or odor in intact male pigs and is primarily attributed to increased concentrations of androstenone and skatole and to a lesser extent by increased indole. The boar taint compounds skatole and indole are produced by gut bacteria, metabolized in the liver, and stored in the fat tissue. Androstenone, on the other hand, is synthesized in the testis along with testosterone and estrogens, which are known to be important factors affecting fertility. The main goal of this study was to investigate the relationship between genetic factors involved in the primary boar taint compounds in an attempt to discover ways to reduce boar taint without decreasing fertility-related compounds. Heritabilities and genetic correlations between traits were estimated for compounds related to boar taint (androstenone, skatole, indole) and reproduction (testosterone, 17ß-estradiol, and estrone sulfate). Heritabilities in the range of 0.47 to 0.67 were detected for androstenone concentrations in both fat and plasma, whereas those for skatole and indole were slightly less (0.27 to 0.41). The genetic correlations between androstenone in plasma and fat were extremely high (0.91 to 0.98) in Duroc and Landrace. In addition, genetic correlations between androstenone (both plasma and fat) and the other sex steroids (estrone sulfate, 17ß-estradiol, and testosterone) were very high, in the range of 0.80 to 0.95. Furthermore, a genome-wide association study (GWA) and a combined linkage disequilibrium and linkage analysis (LDLA) were conducted on 1,533 purebred Landrace and 1,027 purebred Duroc to find genome regions involved in genetic control of the boar taint compounds androstenone, skatole, and indole, and sex hormones related to fertility traits. Up to 3,297 informative SNP markers were included for both breeds, including SNP from several boar taint candidate genes. From the GWA study, we found that altogether 27 regions were significant at a genome-wide level (P < 0.05) and an additional 7 regions were significant at a chromosomal level. From the LDLA study, 7 regions were significant on a genome-wide level and an additional 7 regions were significant at a chromosomal level. The most convincing associations were obtained in 6 regions affecting skatole and indole in fat on chromosomes 1, 2, 3, 7, 13, and 14, 1 region on chromosome 6 affecting androstenone in plasma only, and 5 regions on chromosomes 3, 4, 13, and 15 affecting androstenone, testosterone, and estrogens.

Expression of DLK1 splice variants during porcine adipocyte development in vitro and in vivo.

Delta-like 1 (DLK1) belongs to the epidermal growth factor-like transmembrane protein family and is involved in the regulation of adipogenesis. Several splice variants of DLK1 have been identified in various species, of which two have been previously identified in pig. Here, we present two novel porcine DLK1 splice variants DLK1A and DLK1C. The gene expression profile of these variants together with the previously described DLK1B and DLK1C2 variants was studied in adipose tissue depots of pigs and during adipocyte differentiation in vitro. The short DLK1C and DLK1C2 transcripts were most abundantly expressed and their expression was reduced during porcine adipogenesis.

Expression of 3beta-hydroxysteroid dehydrogenase, cytochrome P450-c17, and sulfotransferase 2B1 proteins in liver and testis of pigs of two breeds: relationship with adipose tissue androstenone concentration.

An excessive accumulation of androstenone in pig adipose tissue is a major contributor to the phenomenon of boar taint. Androstenone deposition is dependent on the rate of androstenone biosynthesis in testis and androstenone degradation in liver. The aim of the current study was to examine the possibility of the existence of breed-specific mechanisms controlling androstenone accumulation in pig adipose tissue. The specific objective was to investigate the expression of some of the key enzymes involved in testicular and hepatic androstenone metabolism in pigs of 2 breeds by using animals with high and low androstenone concentrations within each breed. The study was conducted with Norwegian Landrace (N. Landrace) and Duroc boars. The mean androstenone values for the low- and high-androstenone groups were 0.1 +/- 0.01 microg/g and 7.58 +/- 0.68 microg/g for N. Landrace boars, and 0.22 +/- 0.04 microg/g and 13.55 +/- 1.14 microg/g for Duroc boars. The enzymes investigated were 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450-c17, and sulfotransferase 2B1 (SULT2B1). Expression of cytochrome P450-c17 in liver and testis did not differ between animals with high and low androstenone concentrations in either the N. Landrace or Duroc breed. Expression of hepatic 3beta-HSD, which catalyzes the first stage of androstenone degradation, was decreased in high-androstenone N. Landrace boars (P < 0.01), but not in high-androstenone Duroc boars. In contrast, the expression of hepatic SULT2B1, which catalyzes the second stage of steroid catabolism, was decreased in high-androstenone Duroc animals (P < 0.05), but not in high-androstenone N. Landrace animals. Sulfotransferase 2B1 was also inhibited in testis of high-androstenone pigs of both breeds compared with low-androstenone animals. We report breed differences in expression of the androstenone-metabolizing enzymes 3beta-HSD and SULT2B1 in the liver of high- and low-androstenone pigs. It is suggested that accumulation of androstenone in adipose tissue of N. Landrace boars might be related to a low rate of hepatic androstenone degradation in metabolic stage I, whereas the high androstenone concentration in Duroc boars might be related to a low rate of androstenone metabolism in metabolic stage II.

Investigation of two candidate genes for meat quality traits in a quantitative trait locus region on SSC6: the porcine short heterodimer partner and heart fatty acid binding protein genes.

A highly significant quantitative trait locus (QTL) on pig chromosome 6, affecting intramuscular fat (IMF), has previously been detected by our group and others. Two genes of positional and biological interest, the small heterodimer partner (SHP; NR0B2) and the heart fatty acid binding protein (FABP3; H-FABP), were investigated for meat quality traits and IMF respectively. SHP was partially sequenced (GenBank: DQ002896 and DQ002897) and mapped to the QTL region on porcine chromosome 6, affecting IMF. The map shows no recombination between SHP and FABP3, which was previously mapped to the same QTL region. Twelve single nucleotide polymorphisms were detected in the sequenced region of SHP gene. Haplotype information was used to investigate association between genetic variation and different meat quality traits. SHP haplotype combinations were found to have significant effect on connective tissue. However, further studies are needed to evaluate this possible association more effectively. The FABP3 is involved in fatty acid transport and has been studied as a candidate gene for IMF by several research groups. In our study, FABP3 genotypes were confirmed to be significantly associated with IMF in pigs. The average content of IMF in our population was 1.6%, which may indicate that the FABP3 polymorphism explains as much as 30-35% of the variation in IMF in our pig cross-population.

Fine mapping of a QTL for intramuscular fat on porcine chromosome 6 using combined linkage and linkage disequilibrium mapping.

In this study data from a commercial Norwegian slaughter pig cross was analysed to confirm a previous reported quantitative trait locus (QTL) affecting intramuscular fat (IMF) on porcine chromosome 6. The data consisted of an old experiment, in which the QTL was previously detected, and new experimental data from the Norwegian slaughter pig cross. The old and new experimental data were analysed separately and together. A previously described method combining linkage and linkage disequilibrium analysis (LDLA) was used for the analysis, but this method assumes that all animals are descendants from a common base population, which is not realistic in a cross between different breeds. An adjusted version of the method, able to distinguish between different breeds in the cross, is presented here. Using the LDLA method, we were not able to confirm the QTL in the old experimental data, because the genetic variance could be explained by the polygenic effect. Analysis from the new experimental data did however detect the QTL, and analysing the data from both experiments together gave highly significant results for a QTL (p < 0.001) between markers SW1355 and SW1823. The main conclusion is therefore that the previously reported QTL for IMF on porcine chromosome 6 was confirmed within a 8.7-cM confidence interval.

The effect of parentage on the prevalence, severity and location of lesions of osteochondrosis in swine.

The aims of this study were to determine the effects of parentage and gender on the prevalence, severity and location of lesions of osteochondrosis manifesta (OCM) and osteochondrosis dissecans (OCD) in offspring from different Norwegian Landrace boars and to examine the relationships between lesion characteristics and selected growth parameters. Fifteen sires were selected based on their high breeding value for osteochondrosis. Seven locations in the distal humerus and the distal femur from 1680 offspring of these animals were evaluated for severity of OCM and presence of OCD by gross examination of serially sectioned humeri and femora. Osteochondrosis manifesta was most prevalent in the trochlea of humerus, the sagittal ridge of humerus, the medial condyle of femur and the medial sulcus obliquus of femur. The severity of the lesions and the prevalence of OCD were highest in the trochlea and the sagittal ridge of humerus. Castrates had significantly higher OCM scores than sows. There were significant effects of both sire and dam on the OCM scores of the offspring in most locations; however, growth rate and weight at slaughter did not influence the OCM score.

Investigation of a peroxisome proliferator-activated receptor gamma haplotype effect on meat quality and carcass traits in pigs.

Peroxisome proliferator-activated receptor gamma (PPARG) is a key transcription factor that controls adipocyte differentiation and fat deposition in mammals. The primary goal of this study was to investigate PPARG as a candidate gene for meat quality and carcass traits in swine. Part of the PPARG promoter, along with the most 5'-proximal exon of the gene, was amplified by PCR and subsequently screened for polymorphisms by sequencing. A Met59Val substitution was detected in the porcine PPARG gene along with four polymorphisms in the promoter region of the adipose-specific PPARG2. Three of these polymorphisms were chosen for genotyping and tested for association with meat quality, carcass and growth traits, according to the candidate gene approach. More than 1500 animals from different lines and populations were used in the study with records for meat quality and carcass traits. No convincing associations were found between the traits investigated and the PPARG genotypes. It does not appear that variation at the PPARG locus is affecting meat quality, carcass or growth traits in the pig populations studied.

Tissue distribution of porcine peroxisome proliferator-activated receptor alpha: detection of an alternatively spliced mRNA.

Peroxisome proliferator-activated receptor alpha (PPAR alpha) plays a key role in regulating the catabolic pathway of lipids in response to a variety of compounds named peroxisome proliferators (PPs). The cellular responses to PPs differ among mouse/rat and other species and actualize the study in swine, which show close resemblance to human lipid physiology and metabolism. We have isolated the cDNA containing the open reading frame of porcine PPAR alpha whose deduced amino acid sequence revealed an evolutionary distance to mouse/rat that could be implicated in causing the species-dependent response to PPs. Interestingly, an alternatively spliced PPAR alpha mRNA, lacking exon 5, was detected by reverse transcriptase-polymerase chain reaction in several porcine tissues. This deletion alters the reading frame and introduces a premature stop codon of PPAR alpha, presumably giving rise to a C-terminal truncated protein. We have also examined PPAR alpha expression by Northern blot analysis in tissues taken from pigs at three different stages of maturation, including two breeds that differ considerably in body composition and fat deposition. Porcine PPAR alpha was predominantly expressed in kidney and liver in mature individuals. When comparing piglets of a young age, a breed-specific tissue distribution of PPAR alpha mRNA was observed, particularly in liver and heart.

Detection of quantitative trait loci for meat quality in a commercial slaughter pig cross.

The primary goal of this study was to localize quantitative trait loci (QTL) affecting meat quality traits in swine. In total, 42 traits were scored on 305 F2 individuals from a commercial slaughter pig cross in Norway. F1 and F2 individuals were genotyped for 29 markers on Chromosomes (Chrs) 4, 6, and 7, since previous studies had revealed QTL affecting meat quality traits on these chromosomes. The most evident result was detection of a QTL affecting amount of intramuscular fat on Chr 6. The QTL might also influence tenderness, whereas no effect was observed for back-fat thickness. Additionally, suggestive evidence for QTL affecting other meat quality traits was found on Chr 4 and Chr 7.

Characterisation of porcine peroxisome proliferator-activated receptors gamma 1 and gamma 2: detection of breed and age differences in gene expression.

Two isoforms of peroxisome proliferator-activated receptor gamma (PPAR gamma) cDNAs, gamma 1 and gamma 2, have been isolated and characterised in swine. The relative expression of the two transcripts was studied by northern blot analysis using total RNA isolated from several porcine tissues taken at three different ages (day 1, after 5 weeks and at 100 kg weight). Hybridisation were carried out with two different probes, one binding to both PPAR gamma transcripts and the other being PPAR gamma 2 specific. Strongest hybridisation signals with the PPAR gamma probe binding both variants were detected in adipose tissues and spleen at all three ages, whereas only faint or no signals were detected in other tissues. The tissue distribution pattern of PPAR gamma 1 and gamma 2 suggests a modulation of tissue distribution for the two transcripts and obvious age and breed differences in gene expression in swine.