Abstract: A total of 174 pigs from Shanxi White pig were used to investigate associations between the polymorphic (CA)_n sequence repeat located at the first intron of the insulin-like growth factor (IGF-Ⅰ) gene and the traits of body weights at different growth stages and body sizes at six-month age by unvariate animal model. There were six alleles,which were 198,202,204,206,208 and 210 bp,were detected in Shanxi White population. The frequencies of alleles of 198 and 202 bp,with less CA repeat number,were 0.2759 and 0.2385,respectively,which were greater than those of alleles with more CA repeat number,such as the allele of 208 bp,whose frequency was 0.0747. Twelve genotypes were found in Shanxi White population,the frequencies of homozygotes were greater than 0.010 apart from 208/208 bp,and the frequencies of heterozygotes were 0.017. The associations of IGF-Ⅰ genotype with the traits of birth weight,weaning weight,body weight,body height,body length,chest girth,back fat thickness alive at six-month age were significant (P＜0.05). Individuals with genotype of 204/204 bp has greater body weight and thinner back fat thickness than those of others,which was in accordance with the pig breeding direction in China,should be selected as boars or sows in the selection and breeding programme.

Key words: Shanxi White pig; IGF-Ⅰ gene; microsatellite; body weight; body size