Genetic Status of ESR Locus and Other Unidentified Genes As sociated with Litter Size in Chinese Indigenous Tongcheng Pig Breed after a Long Time Selection

  • Zhu, M.J. ;
  • Yu, M. ;
  • Liu, B. ;
  • Zhu, Z.Z. ;
  • Xiong, T.A. ;
  • Fan, B. ;
  • Xu, S.P. ;
  • Du, Y.Q. ;
  • Peng, Z.Z. ;
  • Li, K.
  • Received : 2003.07.31
  • Accepted : 2004.02.02
  • Published : 2004.05.01


The Tongcheng pig breed is a famous Chinese indigenous breed. The Ministry of Agriculture of China has filed it as 1 of 19 national key conservation breeds selected from more than 100 Chinese indigenous pig breeds in 2000. In order to improve the reproductive performance, it has been intensively selected to increase the litter size for about 10 years. The population randomly sampled from conservation nucleus of eight families in the Tongcheng pigs was genotyped for identification of their estrogen receptor locus polymorphisms with the PCR-RFLPs method. Only AB heterozygotes and BB homozygotes were detected, and $X^2$ test demonstrated that the locus was in disequilibrium at a significant level (p<0.05). In the present paper, the litter sizes in different parities were regarded as different traits. Holistic status of other unspecific and unidentified genes was estimated by using the statistical methods. Coefficients of kurtosis and skewness showed that the litter size still presented segregating characteristic in the 2nd, 5th, 7th, 8th and 9th parities. Analysis of homogeneity of variance between families confirmed the results for the 5th, 7th and 8th parities. The heritability of litter size for the 1st to 10th parities was estimated with paternal half-sib model and individual estimated breeding values (EBVs) were evaluated by a single trait animal model as well. We found that the averages of EBVs for litter size in each parity did not differ significantly between genotypes, despite the significant difference for original phenotype records in the 3rd, 4th and 5th parities (p<0.05 or p<0.01). The results may be explained by the deduction that the polymorphisms of ESR locus are no longer the important genetic base of litter size variation when the frequency of allele B accumulated in the experience of selection procedure, and further conferring that there exist special genes associated with litter size in the recent Tongcheng pigs population can be made.


Chinese Tongcheng Pigs;ESR Locus;Litter Size;Heritability;Breeding Value


  1. Drogemuller, C., H. Hamann and O. Distl. 2001. Candidate gene markers for litter size in different German pig lines. J. Anim. Sci. 79(10):2565-2570.
  2. Gibson, J. P., Z. H. Jiang, J. A. Robinson, A. L. Archibald and C. S. Haley. 2002. No detectable association of the ESR Pvu II mutation with sow productivity in a Meishan${\times}$Large White $F_2$ population. Anim Genet 33(6):448-450.
  3. Isler, B. J., K. M. Irvin, S. M. Neal, S. J. Moeller and M. E. Davis. 2002. Examination of the relationship between the estrogen receptor gene and reproductive traits in swine. J. Anim. Sci. 80(9):2334-2339.
  4. Mo, D. L., B. Liu, Z. G. Wang, S. H. Zhao, M. Yu, B. Fan, M. H. Li, S. L. Yang, G. X. Zhang, T. A. Xiong and K. Li. 2003. Genetic variation and genetic relationship of seventeen Chinese indigenous pig breeds using ten serum protein loci. Asian-Aust. J. Anim. Sci. 16(7):939-945.
  5. Pamilo, P. and S. Varvio-Aho. 1984. Testing genotype frequencies and heterozygosities. Marine Biology 79:99-100.
  6. Pan, P. W., S. H. Zhao, M. Yu, B. Liu, T. A. Xiong and K. Li. 2003. Identification of differentially expressed genes in the longissimus dorsi muscle tissue between duroc and erhualian pigs by mRNA differential displayed. Asian-Aust. J. Anim. Sci. 16(7):1066-1070.
  7. Rothschild, M. F., C. Jacobson and D. Vaske. 1996. The estrogen receptor locus is associated with a major gene influencing litter size in pigs. Proc. Natl. Acad. USA, 93(1):201-205.
  8. Van Rens, B. T., P. N. de Groot and T. van der Lende. The effect of estrogen receptor genotype on litter size and placental traits at term in F2 crossbred gilts. Theriogenology 57(6):1635-1649.
  9. Xu, S. P., Z. Z. Peng, H. M. Wang, P. B. Wu, Y. Q. Du, K. Li and B. Liu. 2001. Present situation of Tongcheng pigs preservation and breeding. Proceedings of 11th national symposium on animal genetics and breeding. Beijing: Chinese Agricultural Scientific Press, In: Research advance of animal genetics and breeding in China. pp. 520-523.
  10. Linville, R. C., D. Pomp, R. K. Johnson and M. F. Rothschild. 2001. Candidate gene analysis for locus affecting litter size and ovulation rate in swine. J. Anim. Sci. 79(1):60-67.
  11. Ledwina, T. and S. Gnot. 1980. Testing for Hardy-Weinberg equilibrium. Biometrics 36:161-165.
  12. Kim, Y., S. C. Woo, G. C. Song, H. Y. Park, B. S. Im and G. W. Kim. 2002. Three-step PCR and RFLP genotyping of the swine ryanodine receptor gene using aged single hair follicles delivered by general mail. Asian-Aust. J. Anim. Sci. 15(9):1237-1243.
  13. Okere, C. and L. Nelson. 2002. Novel reproductive techniques in swine production-a review. Asian-Aust. J. Anim. Sci. 15(3):445-452.
  14. Liu, B., G. Jin, S. Zaho, M. Yu, T. Xiong, Z. Peng and K. Li. 2002. Preparation and analysis of spermatocyte meiotic pachytene bivalents of pigs for gene mapping. Cell Research 12(5-6):401-405.
  15. Van Rens, B. T. and T. van der Lende. 2002. Piglet and placental traits at term in relation to the estrogen receptor genotype in gilts. Theriogenology 57(6):1651-1667.
  16. Kaminski, S., A. Rusc and K. Wojtasik. 2002. Simultaneous identification of ryanodine receptor 1 (RYR1) and estrogen receptor (ESR) genotypes with the multiplex PCR-RFLP method in Polish Large White and Polish Landrace pigs. J. ppl. Genet. 43(3):331-5.
  17. Levene, H. 1960. Robust tests for equality of variances. p. 278-292. In (Ed. Olkin et al.). Contributions to probability and statistics: Essays in honour of Harold Hotelling. Stanford University Press, Stanford.
  18. Short, T. H., M. F. Rothschild, O. I. Southwood, D. G. McLaren, A. de Vries, H. van der Steen, G. R. Eckardt, C. K. Tuggle, J. Helm, D. A. Vaske, A. J. Mileham and G. S. Plastow. 1997. Effect of the estrogen receptor locus on reproduction and production traits in four commercial pig lines. J. Anim. Sci. 75(12):3138-3142.