Abstract: A total of 372 pigs from Duroc, Landrace, Large White, Mashen, Shanxi lean-type SD-Ⅰline, SD-Ⅱ line, SD-Ⅲ line and Shanxi white pig were used to detect the polymorphism within intron 8 of the prolactin receptor gene (PRLR) by PCR-SSCP. Three alleles of A, B, C and four genotypes of AA, AB, AC, and CC were detected in the examined populations. The frequencies of allele A were higher in all examined breeds (lines), ranging from 0.50 to 0.62, than those of allele B, with the range of 0.12 to 0.44. The frequencies of allele C were quite low, ranging from zero to 0.04 in the examined pig populations with the exception of in Duroc (0.26) and in SD-Ⅲ line (0.26). Three transition mutations of G→A,T→C,A→G and insertion mutation of TTT were detected by cloning, sequencing and homologous comparison of the homozygote AA and CC. The records of litter size at first parity of 140 sows and the records of growth and development of 118 replacements of Shanxi white pig were used to investigate the association of PRLR genotype with pig performance by using least square analysis. The results showed that no significant differences both in TNB and NBA at first parity were found among the different PRLR genotype sows. However, the significant associations between PRLR genotype with total teat number, body weight and backfat thickness at the age of six months were detected. The total teat number of individuals with AA genotype was significant higher than those of AC, and the body weight and backfat thickness at six-month age of the replacements with AC genotype was significant higher than those of replacements with AB genotype (P<0.05).

Key words: pig; reproduction traits; growth and development traits; prolactin receptor gene; polymorphism