Erhualian Pigs Research Articles

Evaluating the contribution of gut microbiome to the variance of porcine serum glucose and lipid concentration

Serum glucose and lipids are important indicators for host metabolic condition. Interaction of host and gut microbes regulates the metabolism process. However, how much the gut microbiome contributes to the variance of serum glucose and lipids is largely unknown. Here we carried out a 16S rRNA gene based association study between cecum microbiome and the concentration of serum glucose and lipids in 240 Chinese Erhualian pigs. We identified tens of bacterial taxa associated with serum glucose and lipids. The butyrate-producing bacteria were significantly associated with serum glucose level. The pathogenic bacteria belonging to Proteobacteria and Fusobacteria showed significant associations with increased serum lipid levels, while the bacteria Lactobacillus and Bacilli had negative correlations with serum lipids. Cross-validation analysis revealed that 23.8% variation of serum glucose and 1.6%~6.0% variations of serum lipids were explained by gut microbiome. Furthermore, predicted function capacities related to nutrition intake, transport and carbohydrate metabolism were significantly associated with serum glucose level, while the pathways related to antioxidant metabolism and bile synthesis tended to be associated with serum lipid level. The results provide meaningful information to get insight into the effect of gut microbiome on serum glucose and lipid levels in pigs.

CRISPR/Cas9-mediated knockout of myostatin in Chinese indigenous Erhualian pigs.

CRISPR/Cas9 has emerged as one of the most popular genome editing tools due to its simple design and high efficiency in multiple species. Myostatin (MSTN) negatively regulates skeletal muscle growth and mutations in myostatin cause double-muscled phenotype in various animals. Here, we generated myostatin mutation in Erhualian pigs using a combination of CRISPR/Cas9 and somatic cell nuclear transfer. The protein level of myostatin precursor decreased dramatically in mutant cloned piglets. Unlike myostatin knockout Landrace, which often encountered health issues and died shortly after birth, Erhualian pigs harboring homozygous mutations were viable. Moreover, myostatin knockout Erhualian pigs exhibited partial double-muscled phenotype such as prominent muscular protrusion, wider back and hip compared with wild-type piglets. Genome editing in Chinese indigenous pig breeds thus holds great promise not only for improving growth performance, but also for protecting endangered genetic resources.

The increased expression of follicle-stimulating hormone leads to a decrease of fecundity in transgenic Large White female pigs.

Follicle-stimulating hormone (FSH) is a pituitary gonadotropin regulating reproduction in mammals. Overexpression of the exogenous FSHα/β genes from Chinese Erhualian pigs improved female fecundity of transgenic (TG) mice and male spermatogenesis ability of Large White TG boars. Here, we investigated the impact of the exogenous FSHα/β genes on female reproductive performance of Large White TG pigs. First, we identified the integration site of the exogenous FSHα/β genes at 140,646,456bp on chromosome 9 in these TG pigs using whole-genome sequencing. Then, we showed that TG gilts had higher levels of serum FSH and FSHβ protein in pituitary while had a potentially lower number of born piglets than their wild-type half sibs. TG gilts grew healthily and normally without significant difference in growth and health parameters as compared to WT gilts. The expression levels of FSHR, LHR, ESR1 and ESR2 were significantly lower in TG gilts than in WT gilts at the age of 300days. Taken together, we proposed that the overexpressed FSHα/β transgenes could cause deteriorate fecundity via disturbing the normal expression of the endogenous reproduction-related genes in female pigs. Our findings provide insight into the effect of overexpression of FSHα/β on female reproduction performance in pigs.

Consequences of Epistasis on Growth in an Erhualian × White Duroc Pig Cross.

Epistasis describes an interaction between the effects of loci. We included epistasis in quantitative trait locus (QTL) mapping of growth at a series of ages in a cross of a Chinese pig breed, Erhualian, with a commercial line, White Duroc. Erhualian pigs have much lower growth rates than White Duroc. We improved a method for genomewide testing of epistasis and present a clear analysis workflow. We also suggest a new approach for interpreting epistasis results where significant additive and dominance effects of a locus in specific backgrounds are determined. In total, seventeen QTL were found and eleven showed epistasis. Loci on chromosomes 2, 3, 4 and 7 were highlighted as affecting growth at more than one age or forming an interaction network. Epistasis resulted in both the QTL on chromosomes 3 and 7 having effects in opposite directions. We believe it is the first time for the chromosome 7 locus that an allele from a Chinese breed has been found to decrease growth. The consequences of epistasis were diverse. Results were impacted by using growth rather than body weight as the phenotype and by correcting for an effect of mother. Epistasis made a considerable contribution to growth in this population and modelling epistasis was important for accurately determining QTL effects.

MRNA and protein expression levels of four candidate genes for ear size in Erhualian and Large White pigs

Porcine ear size is an important characteristic for distinguishing among pig breeds. In a previous genome-wide association study of porcine ear size, LEM domain-containing 3 (LEMD3), methionine sulfoxide reductase B3 (MSRB3), high mobility group AT-hook 2 (HMGA2), and Wnt inhibitory factor 1 (WIF1) were implicated as important candidate genes for ear size. This study investigated the expression levels of four candidate genes for ear size in Erhualian and Large White pigs. Ten Erhualian pigs with large ears and eight Large White pigs with small ears at 60 days of age were examined. The mRNA expression levels of the four candidate genes were quantified by real-time polymerase chain reaction. WIF1 mRNA expression was significantly higher in Large White than in Erhualian pigs (P < 0.05), whereas the expression levels of the other three genes were not significantly different between the two breeds. The protein expression levels of the four genes were analyzed using western blot. WIF1 protein expression was significantly higher in Large White than in Erhualian pigs (P < 0.01), whereas MSRB3 protein expression was significantly higher in Erhualian than in Large White pigs (P < 0.05). There were no significant differences between the two breeds in residual protein expression. These results suggest that WIF1 is the main causal gene for ear size in pigs.

Evaluating the Contribution of Gut Microbiota to the Variation of Porcine Fatness with the Cecum and Fecal Samples.

Microbial community in gastrointestinal tract participates in the development of the obesity as well as quite a few metabolic diseases in human. However, there are few studies about the relationship between gut microbiota and porcine fatness. Here, we used high-throughput sequencing to perform 16S rRNA gene analysis in 256 cecum luminal samples from Erhualian pigs and 244 stools from Bamaxiang pigs, and adopted a two-part model statistical method to evaluate the association of gut microbes with porcine fatness. As the results, we identified a total of 6 and 108 operational taxonomic units (OTUs), and 9 and 10 bacterial taxa which showed significant associations with fatness traits in the stool and cecum samples, respectively. Cross-validation analysis indicated that gut microbiome showed the largest effect on abdominal adipose by explaining 2.73% phenotypic variance of abdominal fat weight. Significantly more fatness-associated OTUs were identified in the cecum samples than that in the stools, suggesting that cecum luminal samples were better used for identification of fatness-associated microbes than stools. The fatness-associated OTUs were mainly annotated to Lachnospiraceae, Ruminococcaceae, Prevotella, Treponema, and Bacteroides. These microbes have been reported to produce short-chain fatty acids by fermenting dietary indigested polysaccharide and pectin. The short-chain fatty acids can regulate host body energy homeostasis, protect host from inflammation and inhibit fat mass development. Our findings suggested that the gut microbiome may be an important factor modulating fatness in pigs.

Genome-wide association studies identify susceptibility loci affecting respiratory disease in Chinese Erhualian pigs under natural conditions

Prevalence of swine respiratory disease causes poor growth performance in and serious economic losses to the swine industry. In this study, a categorical trait of enzootic pneumonia-like (EPL) score representing the infection gradient of a respiratory disease, more likely enzootic pneumonia, was recorded in a herd of 332 Chinese Erhualian pigs. According to their EPL scores and the disease effect on weight gains, these pigs were grouped into controls (EPL score≤1) and cases (EPL score>1). The weight gain of the case group reduced significantly at days 180, 210, 240 and 300 as compared to the control group. The heritability of EPL score was estimated to be 0.24 based on the pedigree information using a linear mixed model. All 332 Erhualian pigs and their nine sire parents were genotyped with Illumina Porcine 60K SNP chips. Two genome-wide association studies were performed under a generalized linear mixed model and a case-control model respectively. In total, five loci surpassed the suggestive significance level (P=2.98×10-5 ) on chromosomes 2, 8, 12 and 14. CXCL6, CXCL8, KIT and CTBP2 were highlighted as candidate genes that might play important roles in determining resistance/susceptibility to swine EP-like respiratory disease. The findings advance understanding of the genetic basis of resistance/susceptibility to respiratory disease in pigs.

Identification of new single nucleotide polymorphisms affecting total number born and candidate genes related to ovulation rate in Chinese Erhualian pigs.

The Chinese Erhualian pig has the highest record for litter size in the world. However, the genetic mechanism of its high prolificacy remains poorly understood. In our study, large phenotypic variations in litter size were found among Erhualian sows. Significant differences in total number born (TNB) and corpora lutea numbers were observed between sows with high and low estimated breeding values (EBVs) for TNB. To identify single nucleotide polymorphisms (SNPs) associated with TNB, a selective genomic scan was conducted on 18 sows representing the top 10% and 18 sows representing the bottom 10% of EBVs of 177 sows using Illumina Porcine SNP60 genotype data. Genome-wide fixation coefficient (FST ) values were calculated for each SNP between the high- and low-EBV groups. A total of 154 SNPs were significantly differentiated loci between the two groups. Of the top 10 highest FST SNPs, rs81399474, rs81400131 and rs81405013 on SSC8 and rs81434499 and rs81434489 on SSC 12 corresponded to previously reported QTL for litter size. The other five SNPs, rs81367039 on SSC2, rs80891106 on SSC7, rs81477883 on SSC12 and rs80938898 and rs80971725 on SSC14, appeared to be novel QTL for TNB. Significant associations between rs81399474 on SSC8 and TNB were confirmed in 313 Erhualian sows. Forty genes were identified around the top 10 highest FST SNPs, of which UCHL1, adjacent to rs81399474, and RPS6KB1 and CLTC, adjacent to rs81434499, have been reported to affect the ovulation rate in pig. The findings can advance understanding of the genetic variations in litter size of pigs.

BAC mediated transgenic Large White boars with FSHα/β genes from Chinese Erhualian pigs.

Follicle-stimulating hormone (FSH) is a critical hormone regulating reproduction in mammals. Transgenic mice show that overexpression of FSH can improve female fecundity. Using a bacterial artificial chromosome (BAC) system and somatic cell nuclear transfer, we herein generated 67 Large White transgenic (TG) boars harboring FSHα/β genes from Chinese Erhualian pigs, the most prolific breed in the world. We selected two F0 TG boars for further breeding and conducted molecular characterization and biosafety assessment for F1 boars. We showed that 8-9 copies of exogenous FSHα and 5-6 copies of exogenous FSHβ were integrated into the genome of transgenic pigs. The inheritance of exogenous genes conforms to the Mendel's law of segregation. TG boars had higher levels of serum FSH, FSHα mRNA in multiple tissues, FSHβ protein in pituitary and more germ cells per seminiferous tubule compared with their wild-type half sibs without any reproductive defects. Analysis of growth curve, hematological and biochemical parameters and histopathology illustrated that TG boars grew healthily and normally. By applying 16S rRNA gene sequencing, we demonstrated that exogenous genes had no impact on the bacterial community structures of pig guts. Moreover, foreign gene drift did not occur as verified by horizontal gene transfer. Our findings indicate that overexpression of FSH could improve spermatogenesis ability of boars. This work provides insight into the effect of FSHα/β genes on male reproductive performance on pigs by a BAC-mediated transgenic approach.

Multi-breed genome-wide association study reveals heterogeneous loci associated with loin eye area in pigs.

Numerous quantitative trait loci (QTL) for loin eye area had been identified by linkage mapping studies, but the lack of their precise position hinders their application in the pig breeding industry. To map QTL for loin eye area to a precise genomic region, we conducted a genome-wide association study (GWAS) using Illumina 60K PorcineSNP60 Beadchip in four swine populations: 819F2 pigs, 273 Laiwu pigs, 434 Sutai pigs, and 326 Erhualian pigs. In total, 26 single nucleotide polymorphisms (SNPs) deposited on seven chromosomes associated with loin eye area were identified, 11 of which surpassed the genome-wide significant threshold; of the 11 SNPs, seven located on SSC2 in F2 pigs and four located on SSC12 and SSC18 in Laiwu pigs. Of note, all of the identified QTL were breed specific and no common QTL was identified across the four populations in our study. These findings not only confirmed a previous QTL on SSC2 harboring the candidate gene insulin-like growth factor 2 (IGF2), but also identified some novel candidate genes, far upstream element binding protein 3 (FUBP3), myosin heavy chain (MYH) family, leucine-rich repeats and guanylate kinase domain containing (LRGUK). Our study will contribute to the further identification of the causal mutation underlying these QTL and improve our knowledge of the complex genetic architecture for loin eye area in pigs.

Possible introgression of the VRTN mutation increasing vertebral number, carcass length and teat number from Chinese pigs into European pigs.

Vertnin (VRTN) variants have been associated with the number of thoracic vertebrae in European pigs, but the association has not been evidenced in Chinese indigenous pigs. In this study, we first performed a genome-wide association study in Chinese Erhualian pigs using one VRTN candidate causative mutation and the Illumina Porcine 60K SNP Beadchips. The VRTN mutation is significantly associated with thoracic vertebral number in this population. We further show that the VRTN mutation has pleiotropic and desirable effects on teat number and carcass (body) length across four diverse populations, including Erhualian, White Duroc × Erhualian F2 population, Duroc and Landrace pigs. No association was observed between VRTN genotype and growth and fatness traits in these populations. Therefore, testing for the VRTN mutation in pig breeding schemes would not only increase the number of vertebrae and nipples, but also enlarge body size without undesirable effects on growth and fatness traits, consequently improving pork production. Further, by using whole-genome sequence data, we show that the VRTN mutation was possibly introgressed from Chinese pigs into European pigs. Our results provide another example showing that introgressed Chinese genes greatly contributed to the development and production of modern European pig breeds.

Genome-wide association analyses for meat quality traits in Chinese Erhualian pigs and a Western Duroc × (Landrace × Yorkshire) commercial population.

BackgroundUnderstanding the genetic mechanisms that underlie meat quality traits is essential to improve pork quality. To date, most quantitative trait loci (QTL) analyses have been performed on F2 crosses between outbred pig strains and have led to the identification of numerous QTL. However, because linkage disequilibrium is high in such crosses, QTL mapping precision is unsatisfactory and only a few QTL have been found to segregate within outbred strains, which limits their use to improve animal performance. To detect QTL in outbred pig populations of Chinese and Western origins, we performed genome-wide association studies (GWAS) for meat quality traits in Chinese purebred Erhualian pigs and a Western Duroc × (Landrace × Yorkshire) (DLY) commercial population.MethodsThree hundred and thirty six Chinese Erhualian and 610 DLY pigs were genotyped using the Illumina PorcineSNP60K Beadchip and evaluated for 20 meat quality traits. After quality control, 35 985 and 56 216 single nucleotide polymorphisms (SNPs) were available for the Chinese Erhualian and DLY datasets, respectively, and were used to perform two separate GWAS. We also performed a meta-analysis that combined P-values and effects of 29 516 SNPs that were common to Erhualian, DLY, F2 and Sutai pig populations.ResultsWe detected 28 and nine suggestive SNPs that surpassed the significance level for meat quality in Erhualian and DLY pigs, respectively. Among these SNPs, ss131261254 on pig chromosome 4 (SSC4) was the most significant (P = 7.97E-09) and was associated with drip loss in Erhualian pigs. Our results suggested that at least two QTL on SSC12 and on SSC15 may have pleiotropic effects on several related traits. All the QTL that were detected by GWAS were population-specific, including 12 novel regions. However, the meta-analysis revealed seven novel QTL for meat characteristics, which suggests the existence of common underlying variants that may differ in frequency across populations. These QTL regions contain several relevant candidate genes.ConclusionsThese findings provide valuable insights into the molecular basis of convergent evolution of meat quality traits in Chinese and Western breeds that show divergent phenotypes. They may contribute to genetic improvement of purebreds for crossbred performance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-015-0120-x) contains supplementary material, which is available to authorized users.

Breed-specific lipid-related gene expression in the subcutaneous fat of Large White and Erhualian pigs at weaning

Abstract. The Erhualian (EHL) pig possesses significantly lower growth rates and higher adipose deposition compared with the Large White (LW) pig. To further understand the mechanism of breed lipid deposition difference at the early postnatal age, we employed an animal model of EHL and LW pigs at weaning age to compare the lipid metabolism differences in subcutaneous fat. The result showed that serum triglyceride in EHL was significantly higher (P &lt; 0.05) than that of LW. Peroxisome proliferator-activated receptor-γ protein level in EHL was significantly higher (P &lt; 0.01) though CCTTA enhancer-binding protein level demonstrated no change compared with LW pigs. Hormone sensitive lipase, adipose tissue triglyceride lipase mRNA expression and the lipase activity were significantly lower (P &lt; 0.05) in EHL. Uncoupling protein-2 protein content was significantly lower (P &lt; 0.01) in EHL than that in LW pigs. We first cloned the nucleotide sequence of Zinc-α2-glycoprotein (ZAG) with 1090 bp and found that both ZAG mRNA expression and protein level in EHL pigs was significantly lower (P &lt; 0.01) than that of LW pigs. β3 adrenergic receptor mRNA expression in EHL pigs was significantly higher (P &lt; 0.01) than that of LW pigs, though tumour necrosis factor α gene expression demonstrated no significant difference. Therefore, the significant breed lipid metabolism difference in subcutaneous fat exists at an early postnatal age between EHL and LW pigs, and this difference may originate from two causes including the increased lipid synthesis and reduced lipid mobilization in EHL pigs compared with LW pigs.

Comparison of Fecal Methanogenic Archaeal Community Between Erhualian and Landrace Pigs Using Denaturing Gradient Gel Electrophoresis and Real-Time PCR Analysis

Erhualian and Landrace breeds are typical genetically obese and lean pigs, respectively. To compare the fecal methanogenic Archaeal community between these two pig breeds, fecal samples from different growth phase pigs were collected and used for PCR-denaturing gradient gel electrophoresis (DGGE) with two primer pairs (344fGC/519r and 519f/915rGC) and real-time PCR analysis. Results showed that a better separation and higher quality of bands pattern were obtained in DGGE profiles using primers 344fGC/519r as compared with primers 519f/915rGC. Sequencing of DGGE bands showed that the predominant methanogens in the feces of Erhualian and Landrace pigs belonged to Methanobrevibacter spp. and Methanosphaera spp. Real-time PCR analysis revealed that there was no significant difference in the numbers of fecal total methanogens between Erhualian and Landrace pigs; however, pig growth phase affected the numbers of 16S rRNA genes of total methanogens and Methanobrevibacter smithii. Dissociation curves of methyl coenzyme-M reductase subunit A (mcrA) gene fragments amplified with real-time PCR showed all samples possessed a single peak at 82°C, which might be associated with M. smithii. Samples from the same growth phase of each breed showed good replicative dissociation curves. The results suggest that the growth phase (including diet factor) other than genotype of pig may affect the fecal methanogenic Archaeal community of pigs.

Genetic variants in KDR transcriptional regulatory region affect promoter activity and intramuscular fat deposition in Erhualian pigs

Kinase insert domain receptor (KDR), a vascular endothelial growth factor (VEGF) receptor, is widely regarded as having a principal role in mediating VEGF-induced responses in angiogenesis. As angiogenesis provides oxygen and nutrients for growth and deposition of adipose cells, our objective was to determine whether the promoter polymorphisms in the KDR gene have effects on intramuscular fat (IMF) deposition in the longissimus dorsi muscle. Three novel SNPs, c.-1316A>G, c.-1303C>T and c.-1108A>C, were revealed to have differential allele distribution between high- and low-IMF content groups by comparative sequencing of DNA pools. The three SNPs were completely linked, forming only ACA or GTC haplotypes when genotyped in 105 Erhualian purebred pigs and 98 Duroc × Large White × Yorkshire (D×L×Y) cross-bred pigs. It is interesting that the ACA haplotype is present exclusively in Erhualian pigs and not in D×L×Y pigs. The ACA promoter was found to have higher activity than GTC type for KDR transcription using either gene expression analysis or luciferase assay. Site-direct mutation analysis demonstrated that c.-1316A>G is the causation of promoter activity alteration. Furthermore, we detected that CD31 (also known as PECAM1) and CD34, two blood vessel endothelial markers, expressed higher in ACA/ACA individuals. We concluded that the ACA promoter might be a desirable form for improving IMF content by promoting higher KDR gene expression and more blood vessel network.

Breed-specific expression of GR exon 1 mRNA variants and profile of GR promoter CpG methylation in the hippocampus of newborn piglets

Glucocorticoid receptor (GR) transcription is driven by alternative promoters to produce different exon 1 mRNA variants. CpG methylation on GR promoters profoundly affects GR transcription. GR in hippocampus is critical for energy homeostasis and stress responses, yet it remains unclear whether hippocampal expression of GR exon 1 mRNA variants and the methylation status of GR promoters differ between Large White (LW) and Erhualian (EHL) pigs showing distinct metabolic and stress-coping characteristics. EHL pigs had higher hippocampus weight relative to BW (P<0.01), which was associated with higher serum cortisol level compared with LW pigs. Hippocampal expression of brain-derived neurotrophic factor (P<0.05) was significantly higher, while Bax, a pro-apoptotic gene, was significantly lower in EHL pigs (P<0.05). Hippocampal expression of total GR did not differ between breeds, yet GR exon 1 to 11 mRNA was significantly higher (P<0.01) in EHL pigs, which was associated with a trend of increase (P=0.057) in GR protein content. No significant breed difference was detected for the methylation status across the whole region of the proximal GR promoter, while CpG334 and CpG266.267 were differentially methylated, in a reversed manner, between breeds. The methylation status of CpGs 248, 259, 260, 268 and 271 was negatively correlated (P<0.05) with GR exon 1 to 11 mRNA abundance. Our results provide fundamental information on the breed-specific characteristics of GR and its mRNA variants expression and the status of DNA methylation on the proximal GR promoter in the pig hippocampus.

The novel porcine gene early growth response 4 (Egr4) is differentially expressed in the ovaries of Erhualian and Pietrain pigs

The early growth response 4 (Egr4) gene plays a critical role in human and mouse fertility. In the present study, Affymetrix microarray gene chips were used to evaluate differential gene expression in the ovaries between Erhualian and Pietrain pigs. In all, 487 and 573 transcripts were identified with significantly higher and lower expression, respectively, in Erhualian compared with Pietrain sows. The Egr4 gene, one of the differentially expressed genes, was cloned and its genomic structure was analysed. Egr4 expression is increased 120-fold in ovaries from Erhualian sows. The full-length cDNA of porcine Egr4 was obtained by in silico cloning and 5' rapid amplification of cDNA ends. The gene consists of two exons and its predicted protein contains a Cys2His2 zinc finger structure. The porcine transcript is alternatively spliced by exon sequence deletion, producing two different mRNAs differing at the 5' end of Exon 2. Egr4 transcripts were detected in the central nervous system, including the cerebrum, cerebellum, hypothalamus and pituitary gland, and were highly expressed in the ovary. The Egr4 gene was evaluated as a candidate gene for porcine reproductivity. To investigate the role of Egr4 in the ovary, Egr4 was knocked down using short interference (si) RNA in porcine granulosa cells. Knockdown of Egr4 using siRNA effectively inhibited Egr4 mRNA and protein expression and knockdown significantly affected the expression of Bax, P450arom, P450scc, Egr1, Egr2, and Egr3. In conclusion, these observations establish an important role for Egr4 in the porcine ovary.

Two completely linked polymorphisms in thePPARGtranscriptional regulatory region significantly affect gene expression and intramuscular fat deposition in the longissimus dorsi muscle of Erhualian pigs

This article is the first to report the significant effect of PPARG promoter polymorphisms on the expression and intramuscular fat (IMF) content in the longissimus dorsi (LD) muscle of Erhualian pigs. Polymorphic sites for the PPARG upstream transcriptional regulatory region were scanned by direct sequencing of two DNA pools consisting of individuals with significantly different IMF content (P<0.05). Two SNPs (c.-1633C>T and c.-1572G>A) were identified, with different allele distribution between these two groups. A total of 66 Erhualian pigs and 24 Yorkshire×Large White (Y×L) pigs were genotyped for these two SNPs using PCR-SSCP (single-strand conformation polymorphism), which exhibited that only the T-A and C-G haplotypes existed. The T-A type promoter was found to have higher activity than G-C type promoter for PPARG gene transcription in the induced preadipocytes using luciferase assay. In addition, the frequency of the T-A type in Erhualian pigs was much higher than that in the Y×L pigs (35.6% vs. 8.3%), and in fact, no T-A/T-A samples were found in Y×L pigs. Therefore, we conclude that the T-A haplotype of PPARG is a desirable form that might contribute to the relatively higher IMF content in Erhualian pigs.

Differential gene expression in the endometrium on gestation day 12 provides insight into sow prolificacy

BackgroundErhualian pigs, one of Chinese Taihu pig breeds, are known to have the largest recorded litter size in the world. A lower prenatal death rate is the major contributing factor to the prolificacy of Taihu pigs. Cross-breeding experiments have demonstrated that Taihu sows exhibit a strong maternal effect and that their large litter sizes are mainly caused by maternal genes. The growth and development of porcine embryos on gestation day (GD) 12 are dependent on histotroph secreted by endometrium. Embryonic loss of Taihu pigs on GD12 is lower than that of Western pigs. Here, endometrial samples were collected from pregnant Erhualian sows (parity 3) and Landrace × Large White (LL) sows (parity 3) on GD12. Digital gene expression profiling (DGE) was used to measure the gene expression in the endometrium of the two breeds.ResultsA total of 13,612 genes were differentially expressed between the two breeds (P < 0.001, FDR < 0.001). Gene Ontology (GO) analysis showed that the differential genes involved in reproduction and growth. Pathway analysis revealed that the differentially expressed genes significantly enriched in 24 KEGG pathways. Quantitative real-time RT-PCR confirmed the differential expression of eight genes. Analyses of the differentially expressed genes suggested possible reasons for the difference in embryonic survival ratio between the two breeds. Specifically, these findings point to a higher ratio of PGE2:PGF2α in the endometrium of Erhualian pigs, which facilitates the establishment and maintenance of pregnancy. We also suggest that the differences in the uterine environment lead to higher uterine capacity in Erhualian pigs.ConclusionsThe DGE expression profiles of Erhualian and LL endometrium demonstrated differential expression of genes. Our results will increase understanding of the molecular mechanisms of the low rate of embryonic loss in Chinese Taihu pigs, facilitate the identification of major genes that affect litter size, and be valuable for porcine transcriptomic studies.

Effect of temperature and pH on postmortem color development of porcine M. longissimus dorsi and M. semimembranosus

Purchasing pork that is boned within 1 h postmortem and not aged is customary in China, and final pork color would not be fully realized. The relationship between early postmortem, pre-rigor meat color and 24 h postmortem, post-rigor pork color was investigated and related to the rate of pH and temperature decline within the longissimus dorsi (LD) and the semimembranosus (SM) muscles of pork carcasses. Muscle color, pH and temperature were measured at 45 min and at 3, 9, 15 and 24 h postmortem in carcasses of F₂ White Duroc and Chinese Erhualian pigs. Pork color at 45 min postmortem was not indicative of that at 24 h postmortem in LD and SM, although muscle pH values and temperature at 45 min postmortem were significantly correlated with the LD and SM ultimate color. High muscle pH was associated with decreased L*, whereas high muscle temperature increased L*. Muscle pH and temperature had little effect on a* and b* in LD and color evolution in SM. Results indicated that meat color inspected shortly after slaughter does not reflect post-rigor meat quality.