Effects of dietary amylose and amylopectin ratio on growth performance,meat quality,postmortem glycolysis and muscle fibre type transformation of finishing pigs

The present study was conducted to investigate the effects of dietary amylose and amylopectin ratio on growth performance, meat quality, postmortem glycolysis and muscle fibre type transformation of finishing pigs. Twenty-four barrows (Duroc × Landrace × Yorkshire) with an average initial body weight of 61.7 ± 2.01 kg were randomly assigned to four dietary treatments with amylose: amylopectin ratios of 1:1 (HD), 1:2 (MD), 1:3 (CD) and 1:4 (LD). The results showed that the average daily weight gain of finishing pigs tended to reduce with the ratio of amylose and amylopectin decreased (p = 0.09). Diet LD increased the pH_24h value and decreased the shear force in longissimus dorsi (LM) compared with diet HD (p < 0.05). Diet LD decreased the lactate content and the HK-2 mRNA abundance and increased the mRNA abundance of ATP5B in LM compared with diet HD (p < 0.05). Higher mRNA abundance of MyHC I and lesser abundance of MyHC IIb in LM were found in pigs fed diet CD and LD than those fed diet HD (p < 0.05). Furthermore, pigs fed diet LD had higher mRNA abundances of PGC-1α and PPAR δ in LM than other groups (p < 0.05). These results suggested that diet with low amylose and amylopectin ratio could improve meat quality of finishing pigs via delaying muscle glycolysis capacity and shifting muscle fibre types.     

Molecular Characterization of Five Porcine Candidate Genes for Drip Loss in Pork

Drip loss is the loss of fluid from a piece of meat without mechanical force and represents an important meat quality trait. Previous work revealed a quantitative trait locus (QTL) for drip loss in pork in an experimental Duroc x Piétrain (DUPI) F2 family on SSC 5. Based on functional data indicating their possible involvement in water holding capacity and their expression in skeletal muscle, we selected five positional candidates (ACO2, ADSL, CBY1, KCNJ4, PLA2AG6) out of 130 predicted genes in the QTL interval for further analysis. We performed a mutation analysis of all coding exons and discovered 204 polymorphisms. We genotyped 39 single nucleotide polymorphisms (SNPs) in 192 Piétrain pigs with extreme drip loss phenotypes and detected a possible association with drip loss for one non-coding SNP in the ADSL gene (ss107793818, p_raw = 0.021). Correspondingly, ADSL diplotypes were associated with drip loss and pH1 of M. longissimus dorsi. However, after correction for multiple testing, none of the tested SNPs were significantly associated with drip loss. One possible explanation for these results is that one of the QTL-alleles from the experimental DUPI family may be fixed or nearly fixed in the tested Piétrain population.     

Polymorphism distribution of RYR1, PRKAG3, HFABP,MYF-5 and MC4R genes in crossbred pigs

This study was designed to screen the crossbred pigs for SNPs in five candidate genes, associated with pork quality traits and to differentiate their genotypes by PCR–RFLP. The results indicated that genotypes of crossbred pigs were NN (90%) and Nn (10%) for RYR1; RR (83%) and QR (17%) for PRKAG3; HH (98%), Hh (1%) and hh (1%) for HFABP; DD (99%) and CD (1%) for MYF-5; and AG (57%), GG (26%) and AA (17%) for MC4R SNPs, respectively. Allelic frequencies for five SNPs {RYR1 (1843C>T), PRKAG3 (c.599G>A), HFABP (c.1322C>T), MYF-5 (c.1205A>C) and MC4R (c.1426A>G)} were 0.95 and 0.05 (N/n), 0.08 and 0.92 (Q/R), 0.99 and 0.01 (H/h), 0.00 and 1.00 (C/D) and 0.45 and 0.55 (A/G), respectively. The effect of RYR1 (1843C>T) SNP was significant on pH₄₅ (P?<?0.05), pH₂₄ (P?<?0.05) and protein % (P?<?0.05). The PRKAG3 (c.599G>A) and MC4R (c.1426A>G) SNP had significant association with dressing percentages. The results revealed that RYR1, PRKAG3 and MC4R SNPs may be used in marker associated selection for pork quality traits in crossbred pigs.     

Associations between single nucleotide polymorphisms in 33 candidate genes and meat quality traits in commercial pigs

This study aimed to evaluate the effects of single nucleotide polymorphisms (SNPs) in candidate genes for meat quality using a custom 96‐SNP panel (Illumina Vera Code GoldenGate Assay) on 15 traits collected from 400 commercial pigs. Meat quality measurements included muscle pH, color (L*, a* and b*), drip loss, cooking loss, peak shear force and six sensory traits including appearance (outside and inside), tenderness, juiciness, flavor and overall liking as well as carcass weight and probe yield. Thirty‐five SNPs with minor allele frequencies > 0.10 remained for the multimarker association using the GLM procedure of sas 9.2. Results showed that 20 SNPs were significantly associated with at least one of the traits with either additive or dominance or both effects (P < 0.05). Among these significant SNPs, five of them in ADIPOQ, FTO, TNF, LEPR and AMPD1 had an effect on more than three traits simultaneously; those in MC4R, CAST, DGAT1 and MYF6 had an effect on two traits, while the others were associated with one trait. The results suggest that these markers could be incorporated into commercial pigs for marker‐assisted selection and breeding programs for carcass and meat quality trait improvement.     

The association of haplotypes in IGFBP-3 gene promoter region and tissue expressions in three pig breeds

Bama Xiang pig (BM) and Tibetan mini-pig (TM) are used as experimental animals in China; however, the dwarf molecular mechanisms of these Chinese local pig breeds are unknown. IGFBP-3 affects animal growth, carcass and meat quality. The aim of this study was to identify the polymorphisms in the promoter of the IGFBP-3 and analyse their effect on the IGFBP-3 mRNA expression level in liver and muscle tissues. High-density single-nucleotide polymorphisms (SNPs) (31) and InDels (5) were detected in the promoter of the IGFBP-3 in the BM, TM and Junmu No. 1 White (JM, control) pig breeds from 114 individuals by re-sequencing. A perfect Linkage disequilibrium consisted of 13 SNPs was observed in the promoter region and 2 main haplotypes were identified, of which the h1 genotype (GCA-ATGTACATAT) was more prevalent in JM breed than in TM or BM breeds (P?h2 (ATGTGCACG--CGC) was the dominant haplotype in TM and BM breeds (P?IGFBP-3 mRNA expression level in liver and muscle tissues of pigs. The IGFBP-3 mRNA expression level was determined higher in the liver and muscle tissues of pigs with h2 genotype as compared to that in pigs with h1 genotype (P?IGFBP-3 gene may serve as useful molecular markers for the body growth traits and the breeding in swine.     

Short-term regulation of cytosolic Ca2+, cytosolic pH and vacuolar pH under NaCl stress in the charophyte alga Nitellopsis obtusa

Isolated characean internodal cells of Nitellopsis obtusa can be stored in artificial pond water for many days, but they cannot survive in 100mol m^?3 NaCl solution unless more than several mol m^?3 Ca²⁺ is added. Short-term effects of NaCl stress on the cytosolic concentration of Ca²⁺ ([Ca²⁺]_c), cytosolic pH (pH_c) and vacuolar pH (pH_v) were studied in relation to the external concentration of Ca²⁺ ([Ca²⁺]_e). Changes in [Ca²⁺]_c were measured with light emission from a Ca²⁺-sensitive photoprotein, semisynthetic fch-aequorin which had been injected into the cytosol. Both pH_c and pH_v were measured with double-barrelled pH-sensitive microelectrodes. When internodal cells were treated with 100 mol m^?3 NaCl (0–1 mol m^?3 NaCl (0.1 mol m^?3 [Ca²⁺]_e), [Ca²⁺]_c increased and then recovered to the original level within 60 min. The time course of the transient change in [Ca²⁺]_c was not influenced by the level of [Ca²⁺]_c (0.1 and 10 mol m^?3). In some cases, the transient increase in [Ca²⁺]_c was induced only by increasing external osmotic pressure with sorbitol. In response to treatment with 100 mol m^?3 NaCl (0.1 mol m^?3 [Ca²⁺]_c), pH_c decreased by 0.1–0.2 units after 10min but recovered after 30–60 min, while pH_v increased by 0.4–0.5 units after 2–50 min and tended to recover after 60 min. The initial changes in both pH_c and pH_v were suppressed when [Ca²⁺]_e was raised from 0.1 to 10mol m^?3. These results show that the charophyte alga Nitellopsis can regulate [Ca²⁺]_c, pH_c and pH_v under NaCl stress in the short term and that the protective effect of Ca²⁺ on salinity stress is apparently unrelated to perturbation of Ca²⁺ and pH homeostasis.     

Integrating genome-wide association study with RNA-seq revealed DBI as a good candidate gene for intramuscular fat content in Beijing black pigs

Increasing intramuscular fat (IMF) content can enhance the sensory quality of meat, including tenderness, juiciness, flavor, and color. Genome-wide association study and RNA-sequencing (RNA-seq) analysis were used to identify candidate IMF genes in Beijing Black pigs, a popular species among consumers in northern China. Two and three single nucleotide polymorphisms were significantly associated with IMF in SSC13 and SSC15 respectively. Solute carrier family 4 member 7 (SLC4A7) on SSC13 and insulin induced gene 2 (INSIG2), coiled-coil domain containing 93 (CCDC93), and diazepam binding inhibitor acyl-CoA binding protein (DBI) on SSC15 are good candidate genes in this population. Furthermore, RNA-seq analysis was performed between high and low IMF groups, and 534 differentially expressed genes were identified. In addition, based on differentially expressed genes, Kyoto Encyclopedia of Genes and Genomes analysis revealed that peroxisome proliferator-activated receptors and FoxO signaling pathway pathways might contribute to IMF. Moreover, the DBI gene was identified as a candidate for IMF both by genome-wide association study and RNA-seq analysis, suggesting that it might be a crucial candidate gene for influencing IMF in Beijing Black pigs.     

Research on association between variants and haplotypes of TRPV1 and TRPA1 genes with growth traits in three cattle breeds

The objective of this study was to examine the association of transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) genes polymorphisms with growth traits in three Chinese cattle breeds (Jiaxian red cattle, Qinchuan cattle and Luxi cattle). Through experiments we identified three single nucleotide polymorphisms (SNPs) in these three cattle breeds TRPV1 and TRPA1 genes using PCR-SSCP, (forced) PCR-RFLP methods. Three of these polymorphisms are all synonymous mutation which includes (NW_003104493.1: 30327 C?>?T), (NW_003104493.1: 33394 A?>?G) and (NW_003104493.1: 38471?G?>?A) are in exons. The other three polymorphisms are located at 3'UTR. Furthermore, we evaluated the haplotype frequency and the statistical analyses indicated that these SNPs of TRPV1 and TRPA1 genes were associated with bovine body height, body length, waist angle width, hucklebone width, cross ministry height, chest qingwidth (p?<?0.05) and recommendation height, cannon circumference (p?<?0.01) of Qingchuan cattle; body length, waist angle width (p?<?0.05) of Jiaxian red cattle; body weight, Body length, cannon circumference, chest circumference (p?<?0.05) and body height (p?<?0.01) of Luxi cattle. Our result confirms the polymorphisms in the TRPV1 and TRPA1 genes are associated with growth traits that may be used for marker-assisted selection (MAS) in three beef breeds programs.     

Genome‐wide association study identifies markers associated with meat ultimate pH in Duroc pigs

In this study we aimed to identify genomic regions associated with muscle pH, meat colour and water‐holding capacity in a population of 280 Italian Duroc pigs genotyped by the Illumina PorcineSNP60 v2 Genotyping BeadChip. After quality control, the remaining 32 597 SNPs and 278 subjects were used to perform a genome‐wide association study with the genabel package, using a kinship matrix in a model with the effects of sex, age and slaughter day. Bonferroni correction was applied, and the significant markers and regions were then further investigated to identify the nearest genes and the linkage disequilibrium (LD) between markers. Four markers (ASGA0082344, ASGA0095635, DBWU0000985 and CASI0005117) were significantly associated with ultimate pH (pH_u); no significant association was detected for the other traits. The four significant variants, located from 16.841 to 17.643 Mb on chromosome 3, were found within or close to the sequences of the sulfatase modifying factor 2 (SUMF2), lysine acetyltransferase 8 (KAT8), serine protease 8 (PRSS8) and phosphorylase kinase catalytic subunit gamma 2 (PHKG2) genes. The four associated markers lie in two LD blocks, suggesting that the observed effect is related to mutations located in two regions: the first one where SUMF2 is mapped and the second one where genes KAT8, PRSS8 and PHKG2 are located.     

The porcine <Emphasis Type="Italic">TBC1D1</Emphasis> gene: mapping,SNP identification,and association study with meat,carcass and production traits in Italian heavy pigs

TBC1D1 [TBC1 (tre-2/USP6, BUB2, cdc16) domain family, member 1] is a Rab-GTPase-activating related protein implicated in regulating the trafficking of glucose transporter 4 (GLUT4 or SLC2A4) storage vesicles to the cell surface in response to insulin and AMPK-activating stimuli in skeletal muscle. Mutations in the human and mouse TBC1D1 genes confer risk of obesity or leanness. We identified five single nucleotide polymorphisms (SNPs) in the porcine TBC1D1 gene. One of them (FN677935:g.219G>A) was genotyped either by high resolution melting and PCR-RFLP analyses to study allele frequencies in a few pig breeds and evaluate association with meat production and carcass traits in five groups of sib-tested pigs of Italian Large White and Italian Duroc breeds. The g.219G>A SNP was associated (P < 0.05) with ham weight, back fat thickness and lean cuts content in Italian Large White and with visible intermuscular fat in Italian Duroc pigs.     

Genomic variants associated with the number and diameter of muscle fibers in pigs as revealed by a genome-wide association study

Muscle fiber characteristics comprise a set of complex traits that influence the mea quality and lean meat production of livestock. However, the genetic and biological mechanisms regulating muscle fiber characteristics are largely unknown in pigs. Based on a genome-wide association study (GWAS) performed on 421 Large White × Min pig F2 individuals presenting well-characterized phenotypes, this work aimed to detect genome variations and candidate genes for five muscle fiber characteristics: percentage of type I fibers (FIB1P), percentage of type IIA fibers (FIB2AP), percentage of type IIB fibers (FIB2BP), diameter of muscle fibers (DIAMF) and number of muscle fibers per unit area (NUMMF). The GWAS used the Illumina Porcine SNP60K genotypic data, which were analyzed by a mixed model. Seven and 10 single nucleotide polymorphisms (SNPs) were significantly associated with DIAMF and NUMMF, respectively (P < 1.10E-06); no SNP was significantly associated with FIB1P, FIB2AP or FIB2B. For DIAMF, the significant SNPs on chromosome 4 were located in the previously reported quantitative trait loci (QTL) interval. Because the significant SNPs on chromosome 6 were not mapped in the previously reported QTL interval, a putative novel QTL was suggested for this locus. None of the previously reported QTL intervals on chromosomes 6 and 14 harbored significant SNPs for NUMMF; thus, new potential QTLs on these two chromosomes are suggested in the present work. The most significant SNPs associated with DIAMF (ALGA0025682) and NUMMF (MARC0046984) explained 12.02% and 11.59% of the phenotypic variation of these traits, respectively. In addition, both SNPs were validated as associated with DIAMF and NUMMF in Beijing Black pigs (P < 0.01). Some candidate genes or non-coding RNAs, such as solute carrier family 44 member 5 and miR-124a-1 for DIAMF, and coiled-coil serine rich protein 2 for NUMMF, were identified based on their close location to the significant SNPs. This study revealed some genome-wide association variants for muscle fiber characteristics, and it provides valuable information to discover the genetic mechanisms controlling these traits in pigs.     

Mitochondria,sex and variation in routine metabolic rate

Variation in the metabolic costs associated with organismal maintenance may play a key role in determining fitness, and thus these differences among individuals are likely to be subject to natural selection. Although the evolvability of maintenance metabolism depends on its underlying genetic architecture, relatively little is known about the nature of genetic variation that underlies this trait. To address this, we measured variation in routine metabolic rate (?O_2routine), an index of maintenance metabolism, within and among three populations of Atlantic killifish, Fundulus heteroclitus, including a population from a region of genetic admixture between two subspecies. Polygenic association tests among individuals from the admixed population identified 54 single nucleotide polymorphisms (SNPs) that were associated with ?O_2routine, and these SNPs accounted for 43% of interindividual variation in this trait. However, genetic associations with ?O_2routine involved different SNPs if females and males were analysed separately, and there was a sex‐dependent effect of mitochondrial genotype on variation in routine metabolism. These results imply that there are sex‐specific genetic mechanisms, and potential mitonuclear interactions, that underlie variation in ?O_2routine. Additionally, there was evidence for epistatic interactions between 17% of the possible pairs of trait‐associated SNPs, suggesting that epistatic effects on ?O_2routine are common. These data demonstrate not only that phenotypic variation in this ecologically important trait has a polygenic basis with considerable epistasis among loci, but also that these underlying genetic mechanisms, and particularly the role of mitochondrial genotype, may be sex‐specific.     

Genome-wide association study identifies loci and candidate genes for meat quality traits in Simmental beef cattle

Improving meat quality is the best way to enhance profitability and strengthen competitiveness in beef industry. Identification of genetic variants that control beef quality traits can help breeders design optimal breeding programs to achieve this goal. We carried out a genome-wide association study for meat quality traits in 1141 Simmental cattle using the Illumina Bovine HD 770K SNP array to identify the candidate genes and genomic regions associated with meat quality traits for beef cattle, including fat color, meat color, marbling score, longissimus muscle area, and shear force. In our study, we identified twenty significant single-nucleotide polymorphisms (SNPs) (p < 1.47 × 10^?6) associated with these five meat quality traits. Notably, we observed several SNPs were in or near eleven genes which have been reported previously, including TMEM236, SORL1, TRDN, S100A10, AP2S1, KCTD16, LOC506594, DHX15, LAMA4, PREX1, and BRINP3. We identified a haplotype block on BTA13 containing five significant SNPs associated with fat color trait. We also found one of 19 SNPs was associated with multiple traits (shear force and longissimus muscle area) on BTA7. Our results offer valuable insights to further explore the potential mechanism of meat quality traits in Simmental beef cattle.     

Seawater pH,and not inorganic nitrogen source,affects pH at the blade surface of Macrocystis pyrifera: implications for responses of the giant kelp to future oceanic conditions

Ocean acidification (OA), the ongoing decline in seawater pH, is predicted to have wide‐ranging effects on marine organisms and ecosystems. For seaweeds, the pH at the thallus surface, within the diffusion boundary layer (DBL), is one of the factors controlling their response to OA. Surface pH is controlled by both the pH of the bulk seawater and by the seaweeds' metabolism: photosynthesis and respiration increase and decrease pH within the DBL (pH_DBL), respectively. However, other metabolic processes, especially the uptake of inorganic nitrogen (N_i; NO₃^? and NH₄⁺) may also affect the pH_DBL. Using Macrocystis pyrifera, we hypothesized that (1) NO₃^? uptake will increase the pH_DBL, whereas NH₄⁺ uptake will decrease it, (2) if NO₃^? is cotransported with H⁺, increases in pH_DBL would be greater under an OA treatment (pH = 7.65) than under an ambient treatment (pH = 8.00), and (3) decreases in pH_DBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H⁺] might affect the strength of the diffusion gradient. Overall, N_i source did not affect the pH_DBL. However, increases in pH_DBL were greater at pH 7.65 than at pH 8.00. CO₂ uptake was higher at pH 7.65 than at pH 8.00, whereas HCO₃^? uptake was unaffected by pH. Photosynthesis and respiration control pH_DBL rather than N_i uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and N_i uptake will not be affected by a reduced pH.     

Identification of four SNPs and association analysis with meat quality traits in the porcine <Emphasis Type="Italic">Pitx2c</Emphasis> gene

The association of the porcine Pitx2c gene with meat quality traits was investigated in the present study. A total of eight single nucleotide polymorphisms (SNPs) were found. Allele frequencies of four SNPs were further detected in four commercial breeds and eight Chinese indigenous breeds. Single SNP and meat quality associations were analyzed in a Yorkshire×Meishan F₂ population. The SNPs c.474C>T (P<0.01) and c.636C>T (P<0.05) showed a significant association with meat color (MCV1). The SNPs c.*37G>A and c.*47G>A were significantly associated with drip loss rate (DLR), water holding capacity (WHC) and meat color value (MCV1) consistently (P<0.05). Linkage disequilibrium (LD) analysis revealed that the adjacent SNPs were in LD. Two major haplotypes were identified, and association analysis between haplotype combinations and meat quality indicated that the presence of two copies of haplotype 1 -CCGG- may improve meat quality.     

Association analyses of porcine SERPINE1 reveal sex-specific effects on muscling, growth, fat accretion and meat quality

The serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1), member 1 (SERPINE1) gene encodes plasminogen activator inhibitor type 1 (PAI), which is the major physiological inhibitor of tissue‐type and urokinase‐type plasminogen activators and plays a role in obesity and insulin resistance in women but not in men. We detected SNP FN396538:g.566G>A in intron 3 and a non‐synonymous substitution NM_213910:c.612A>G in exon 3 (p.Ile159Val) and mapped the gene to position 8.4 cM on the linkage map of chromosome 3. Association analyses were conducted on the 12th–15th generation of the Meishan × Large White (MLW) cross (n = 565), with records for weight at the end of test, lifetime daily gain, test time daily gain, loin depth and backfat depth, as well as on a European wild boar × Meishan (W × M) F₂ population (n = 333) with 47 traits recorded for carcass composition and meat quality. Analyses performed across the entire MLW population or in the male animals did not show any trait significantly associated with the loci studied. In female animals, both SNPs were associated with loin depth at nominal P < 0.05 with adjusted P values equal to 0.051 (g.566) and 0.057 (c.612). Differences between homozygotes were up to 0.65 SD. In the entire W × M population and female animals, SERPINE1 was significantly associated at adjusted P < 0.05 in descending order with muscling, growth and fat accretion and in male animals with meat quality (R‐value). In the studied populations, allele effects were in opposite directions, which implies that the SNPs are markers that are in linkage disequilibrium with a causative mutation.     

Association of polymorphisms in calpain 1, (mu/I) large subunit,calpastatin, and cathepsin D genes with meat quality traits in double‐muscled Piemontese cattle

Five single‐nucleotide polymorphisms (SNPs) located in the calpain 1, (mu/I) large subunit (CAPN1), calpastatin (CAST), and cathepsin D (CTSD) genes were analyzed in a large sample of Piemontese cattle. The aim of this study was to evaluate allele and genotype frequencies of these SNPs and to investigate associations of CAPN1, CAST, and CTSD gene variants with meat quality traits. Minor allele frequencies ranged from 30 to 48%. The presence of the A allele at CAPN530 increased yellowness and drip loss. The CAST282 G allele was associated with an increased drip loss compared to the C allele, and the CAST2959 A allele decreased redness compared to the G allele.     

Polymorphism identification in GDF9 gene and its association analysis with reproduction traits in Jinghai Yellow chicken

Abstract

GDF9 (growth differentiation factor 9) belongs to the transforming growth factor-β (TGF-β) superfamily and plays an irreplaceable role in female fertility. To reveal its genetic effects on productivity performance in chickens, 373 Jinghai Yellow chickens were chosen randomly to detect SNPs in GDF9 by PCR-SSCP and DNA sequencing methods. Eventually, four SNPs (g.2053G?>?A, g.2275T?>?C, g.2338C?>?T, g.2420T?>?C) in total had been detected. Amongst them, g.2420T?>?C was first found significantly associated with reproduction trait in chickens and heterozygous type C₂T₂ had higher average egg weight at 300?days of age (AEWD300) than T₂T₂ (p?<?0.01). Least squares analysis showed that age at first laying (AFE) of H1 and H1H1 chickens were significantly earlier than that of H7 and H7H7 ones, respectively (p?<?0.05). H1H5 hens showed higher AEWD300 than H4H7 ones (p?<?0.05). For total egg number at 300?days of age (END300), mean of H5H5 was significantly higher than that of H4H4 (p?<?0.05). Hence, the study suggested that hybrid vigor at g.2420T?>?C could be utilized in practice. H1H1, H1H5 and H5H5 could be the dominant diplotypes for chicken breeding. The study may contribute to the breeding progress of productive chickens and supply reference for oviparous animal production practice.     

Association of 3 polymorphisms in porcine troponin I genes (TNNI1 andTNNI2) with meat quality traits

The contractile protein troponin I (TnI), a constituent protein of the troponin complex located on the thin filaments of striated muscle, is involved in inhibition of calcium-induced myosin AT Pase activity (and thus contraction). TnI-slow (slow-twitch skeletal muscle isoform, named TNNI1) and TnI-fast (fast-twitch skeletal muscle isoform, named TNNI2) are muscle-fiber-type-specific proteins, and expression of their genes may affect the composition of muscle fiber, thereby influencing the meat quality traits. Thus, the TnI genes are potential candidate genes for traits related to meat quality in animals. Association of 2 SNPs (EU743939:g.5174T>C in intron 4, and EU743939:g.8350C>A in intron 7) of theTNNI1 gene and a SNP (EU696779:g.1167C>T in intron 3) of theTNNI2 gene with 11 meat quality traits were studied on 334 Large White × Meishan F₂ pigs. In theTNNI1 gene, g.5174T>C and g.8350C>A were found to be significantly associated with intramuscular fat content and meat color value of biceps femoris. The g.5174T>C also showed significant effects on meat color value and marbling score of longissimus dorsi, as well as pH of longissimus dorsi and semispinalis capitis. The g.1167C>T polymorphism in theTNNI2 gene affected significantly the pH of longissimus dorsi, meat color value of longissimus dorsi and semispinalis capitis, marbling score of longissimus dorsi, and intramuscular fat.