| Bactericidal/permeability-increasing protein (BPI) is a high affinity for LPS of Gram-negative bacteria. Bind of BPI to susceptible bacteria is followed by increasing outer membrane permeability, inhibition of growth and ultimately, irreversible loss of viability. In addition, BPI also possesses an opsonic function. Because of these important functions, BPI plays an important role in host initial defense. Many studies have confirmed that several polymorphic sites were found in exon 3 and exon 4 of BPI gene in livestock and poultry. It has been shown that the antibiotic and endotoxin-neu-tralizing functions of BPI are fully recovered with the exon 3 regions, and that the restriction fragment length polymorphism sites in exon 4 of porcine BPI gene are related to the susceptibility of Salmonella cholerasuis in several pig breeds.PCR-SSCP analysis was used to analyse the polymorphism within exon 3 and exon 4 of the porcine BPI gene on 81 Rongchang pigs population which were reared in same conditions. Both blood count (WBC,LYM%,MID%,GRAN%,LYM,MID,GRAN,RBC,HGB,HCT,MCV,MCH,MCHC,RDW-SD,RDW-CV,PLT,MPV,PDW,PCT and P-LCR) and IgG were measured in its 60 day-old.5 pigs were selected from each combination genotype (n=5) of exon 3 and exon 4 of BPI gene for challenge. Pigs were grown to 70 days of age to oral challenge with 70 billion live Escherichia coli, and analysed difference in values of immune traits (WBC,RRAN,LYM,MID,LYM% and MID%) before and after challenge. The results as follows:(1) The polymorphism of exon 3 and exon 4 of Rongchang pig were analysed. There were two genotypes (GG and HH, respectively) in exon 3 of Rongchang pig BPI gene, and the frequency of genotype was 0.67 and 0.33, respectively. The frequency of gene (G and H, respectively) and genotype were similar in exon 3. There were four genotypes (AA, BB, BC and CC, respectively) in exon 4, and frequency of genotype was 0.57,0.26,0.16 and 0.01, respectively. The gene frequency of A, B and C was 0.57,0.34 and 0.09, respectively. There were six combination genotypes (GGAA,GGBB,GGBC,HHAA and HHBB), and the frequency of genotypes was 0.30,0.21,0.15,0.27,0.06 and 0.01.(2) Association of BPI gene polymorphism with blood count and immune traits were analysed by SPSS software and the results showed that the value of P-LCR of GG genotype was higher than HH genotype in exon 3 of Rongchang pig BPI gene (P＜0.05). There were no significant differences between the other genotypes (P>0.05). The values of RDW-SD and RDW-CV of BB genotype were higher than the other two genotypes in exon 4 of Rongchang pig BPI gene (P＜0.05). There were no significant differences between the other genotypes (P>0.05). The values of WBC and MID of GGBC,HHAA and HHBB genotypes were higher than the values of GGAA and GGBB (P＜0.05), and the value of MID of GGAA genotype was higher than the value of GGBB (P＜0.05). The values of RDW-SD and RDW-CV of GGBB,HHAA and HHBB genotypes were higher than the value of GGAA and GGBC (P＜0.05). The values of MCV of GGBB,GGBC and HHAA were higher than the values of GGAA and HHBB (P＜0.05). There were no significant differences between the other combination genotypes (P>0.05).(3) Effect of BPI genotype on resistance capacity was analysed and the results showed that the values after challenge of LYM and LYM% of HH genotype were lower than the value before chall-enge of theirs (P＜0.05). The values after challenge of RRAN,LYM and MID% of AA genotype were lower than the value before challenge of theirs (P＜0.05). The values after challenge of LYM% and MID% were lower than the value before challenge of theirs (P＜0.05). The values after challenge of WBC,RRAN,LYM#,MID,LYM% and MID% of HHBB genotype were significantly lower than the value before challenge of theirs (P＜0.01). The values after challenge of WBC and LYM were lower than the value before challenge of theirs (P＜0.05). The diffences in values differences before and after challenge of WBC and LYM of HH were significantly higher than GG genotype in exon 3 of Rongchang pig BPI gene (P＜0.01). There were no significant differences between the other genotypes (P>0.05).
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