Higher Tolerance of Min Pigs Under Cold Stress:An Assessment from Reproduction Perspective

Raising Min pigs(MPs)in northern China is challenging,because of harsh environmental conditions in winter.There is a hypothesis that MPs can tolerate cold stress better than Large White pigs(LWPs)and their oocyte competence is particularly protected.Over a period of 3 years,multiple cohorts of MPs and LWPs under different environmental conditions were studied in this paper.Follistatin(FST)serum level was used as a marker for swine oocyte competence.Oocytes were collected from the swine and their maturation rate,cleavage rate and blastocyst rate were measured.Lastly,mRNA expression in ovary and longissimus dorsi for the genes FST,luteinizing hormone receptor(LHR)and cold-inducible RNA-binding protein(CIRP)was measured.Under cold stress,serum follistatin concentrations of both LWPs and MPs were markedly increased,and they were more in LWPs than in MPs.However,oocyte competence was found to be unaffected by cold stress in MPs.It was found that in a separate group of LWPs,oocyte competence was lower in samples collected in winter than that in other seasons.Interestingly,follistatin levels in the follicular fluid of MPs showed no change with cold stress,and serum follistatin levels were increased in sows.Gene expression analysis showed a significant reduction in FST,LHR and CIRP expressions under cold stress in longissimus dorsi,but not in the ovaries.It was found that MPs were better able to maintain oocyte competence under cold stress,which might be due to improved regulation of follistatin in follicular fluid,and MPs appeared likely an adaptation to the harsh conditions that they faced under domestication in northern China.

Cloning and Sequence Analysis of Y-box Binding Protein Gene in Min Pig

In order to study the gene sequence of Min pig Y-box binding protein （YB-1） gene, the complete coding sequence of Min pig YB-1 gene was cloned by RT-PCR, the sequence features were analyzed by some software and online website. The results showed that the complete CDS of Min pig Y-box was found to be 975 bp long, encoding 324 amino acids. It contained a conserved cold shock domain and several phosphorylation sites, but had no transmembrane domains, and was consistent with a protein found in the cytoplasm. Min pig YB-1 nucleotides shared high similarity （61.37%- 97.66%） with other mammals.

Genetic Application of Analysis on Testosterone Secretion after Fourier Conversion

adult Min sows from 9 sire families were used in this experiment and blood samples were taken from the tail at 10 minute intervals at 9∶00～11∶00 AM on the 6th day after mating. The content of testosterone in the blood during this period was measured by radio-immunological assay(RIA) and was coverted into the amplitude through Fourier conversion. The heritalilities of amplitude for 3rd, 4th and 5th partial waves of testosterone secretion were high, being 0.507, 0.706 and 0.725 respectively, and a relatively high genetic correlation coefficient of -0.423 and -0.742 was found between the amplitude for the 1st and 3rd partial waves of testosterone secretion and the litter size. The highest coefficients of were found between for 1st, 4th and 5th partial waves and the litter size alive (-0.87, -0.822 and -0.742) and between these amplitudes and the estrous duration (-0.96, -0.816 and -0.805). Therefore it is concluded that lowing the amplitudes of testosterone secretion through artificial selection could improve the reproductive performance of Min sows, especially for the high frequency signals such as those for the 4th, 5th partial waves in this experiment.