Identifying SNPs associated with birth weight and days to 100 kg traits in Yorkshire pigs based on genotyping-by-sequencing

Birth weight(BW)and days to 100 kg(D100)are important economic traits that are both affected by polygenes.However,the genetic architecture of these quantitative traits is still elusive.Genotyping-by-sequencing(GBS)data containing a large number of single nucleotide polymorphisms(SNPs)have become a powerful tool in genomic analysis.To better understand their complex genetic structure,a total of 600 Yorkshire pigs were sequenced using GBS technology.After quality control,279787 SNPs were generated for subsequent genome-wide association study(GWAS).A total of 30 genome-wide SNPs(P<1.79 E–07)were identified for D100.Furthermore,a total of 22 and 2 suggestive SNPs(P<3.57 E–06)were detected for D100 and BW,respectively.Of these,one locus located on SSC12(position:46226512 bp)were evaluated to affect both BW and D100 in Yorkshire pigs,indicating the pleiotropism in different traits.Considering the function of candidate genes,two genes,NSRP1 and DOCK7,were suggested as the most promising candidate genes involved in growth traits.Thus,use of GBS is able to identify novel variants and potential candidate genes for BW and D100,and provide an opportunity for improving pig growth traits using genomic selection in pigs.

Comparison of Muscle Fiber Growth from F1Generations of Large Yorkshire Pig andErhualian Pig by Reciprocal Cross

[ Objective] To compare the muscle fiber growth between F1 generations of large Yorkshire pig and Erhualian pig by reciprocal cross, and provide a theoretical basis for the integrated breeding of meat quality traits and growth performances by rational utilization of hybrid combination. [ Method] The hybrid pigs of large Yorkshire pig and Erhualian pig were fed and managed in the same conditions. The reciprocal combinations were Erhualian pig ♀ × Yorkshire pigd, and Yorkshire pig ♀ × Erhualian pig♂ , respectively. At the age of 20, 70, 120 and 180 d, the Iongissimus dorsi muscle and thigh muscle were collected and made into frozen sections for hematoxylin and eosin （HE） staining, and then the muscle fiber area was determined. [ Result] The muscle fiber was thickened gradually with increasing age; and the absolute growth curve of muscle fiber area was presented as ＂S＂ shape. The diameter, perimeter and area of Iongissimus dorsi muscle and thigh muscle fibers in the reciprocal combination of Yorkshire pig ♀ × Erhualian pig♂ were higher than those in the reciprocal combination of Erhualian pig ♀ × Yorkshire pig♂ （P 〈 0.01 ）. The thigh muscle grew faster than Iongissimus dorsi muscle at the age of 20 -120 d; but at the age of 120 -180 d, the growth rate of Iongissimus dorsi muscle was higher than that of thigh muscle; and at the age of 180 d, the muscle fiber area had no significant difference between the Iongissimus dorsi muscle and the thigh muscle. The muscle fiber area had extremely significant difference between the reciprocal combinations at the age of 20 d; but no significant difference was found at the age of 180 d. [ Conclusion] The reciprocal combinations can affect the muscle fiber growth of hybrid pigs of Yorkshire pig and Erhualian pig, but the affect degree reduces with the increasing age.

Comparisons of carcass traits,meat quality,and serum metabolome between Shaziling and Yorkshire pigs

This study aims to compare the meat quality of Shaziling and Yorkshire pigs and to find the potential indicator in serum for superior meat quality.Six Shaziling and Yorkshire pigs at 30,60,90,150,210,and 300 d of age were selected to examine carcass traits,meat quality,and serum metabolome.The results showed that the body weight,carcass length,and loin eye area of Shaziling pigs at 150,210,and 300 d of age were significantly lower than those of Yorkshire pigs(P<0.05).Shaziling pigs at 150 and 300 d of age had significantly lower backfat thickness than Yorkshire pigs(P<0.05).Compared with Yorkshire pigs,Shaziling pigs at all 6 ages had a lower lean percentage and a higher fat percentage(P<0.05).At 60,90,and 150 d of age,the post-mortem pH-decline,b*value(yellowness),and drip loss of Shaziling pigs were significantly lower than those of Yorkshire pigs(P<0.05).Moreover,at 150 d of age,Shaziling pigs had significantly higher a^(*)value(redness)and intramuscular fat(IMF)content than Yorkshire pigs(P<0.05).Correlation analysis between the top 40 metabolites and phenotypes indicated that L-carnitine had positive correlations with fat percentage,pH24h,and IMF content,but had negative correlations with lean percentage,L^(*)value(lightness),and b^(*)value(P<0.05).Serum L-carnitine content,fat percentage,pH24h,and IMF content all decreased first and then increased as the pigs grew,which verified the positive correlations between L-carnitine and these phenotypes.In conclusion,Shaziling pigs have a slower growth rate but a better meat quality than Yorkshire pigs.The meat quality of Shaziling pigs is the best from 150 to 210 d of age.This study suggests that a higher serum L-carnitine content is a promising indicator for better meat quality.

Study on PRRSV Receptor Genes Differential Expression in Lung Tissues in Different Breeds of Pigs after Infecting with HP-PRRSV

[ Objective] In order to study the susceptibility molecular mechanism of highly pathogenic porcine reproductive and respiratory syndrome virus （ HP- PRRSV） JXA1 isolate on Tibetan pig, Zangmei pig and Yorkshire pig. [ Method ] In the study, real-time quantitative RT-PCR method was established to compare and analyze the differential expression of five porcine reproductive and respiratory syndrome virus （PRRSV） receptor genes （HSPG2, SIGLEC1, CD163, VIM and NMMHC-H A） in lung tissues in Tibetan pig, Zangmei pig and Yorkshire pig before the challenge and at the 4th ,7th and 14th days after the challenge with JXAI isolate. [ Results ] HSPG2 expression in Tibetan pig lung tissues increased significantly at the 4th and 14th days after the challenge with JXAI （ P 〈 0.05 ）, while decreased significantly at the 7th day after the challenge （P 〈 0.05 ）, HSPG2 expression in Zangmei pig lung tissues increased significantly at the 14th day after the challenge （P〈0.05）. SIGLECl expression in Tibetan pig lung tissues increased significantly at the 4th and 14th days after the infection（P 〈 0.05 ）, while SIGLEC 1 expression in Yorkshire pig decreased significantly at the 4th, 7th and 14th days after the challenge （P 〈0. 05 ）. CD163 expression in lung tissues of Tibetan pig and Zangmei pig both increased significantly at the 14th day after the challenge （P 〈 0.05 ）, while CD163 expression in lung tissues of Yorkshire pig decreased significantly at the 7th and 14th days after the challenge （ P 〈 0. 05 ）. VIM expression in lung tissues of Tibetan pig increased significantly at the 7th day after the challenge （ P 〈 0. 05 ）, while which of Yorkshire pig at the 7th day after the challenge decreased significantly （ P 〈 0. 05 ）. NMMHC-II A expression in lung tissues of Zangmei pig increased significantly at the 4th day after the challenge （ P 〈 0. 05 ）, and which of Yorkshire pig increased significantly at the 4th and 14th days after the challenge （P 〈 0. 05 ）. [ Conclusion] SIGLEC1 and VIM genes might be the potential key genes affecting the susceptibility of JXA1 isolate on Tibetan pig, Zangrnei pig and Yorkshire pig. Key words JXA1 isolate; Tibetan pig; Zangmei pig; Yorkshire pig; Porcine reproductive and respiratory syndrome virus receptor genes; Differential expression