| To study the gene expression rules of antibacterial peptides PR-39 andProtegrin-1 in thymus gland, spleen, lymphonodi mesosteniales and bone marrow inpiglets of various days-age, and to investgate the effects of weaning and addingpolysaccharides compound to the diet on their genes expression, the special primersfor PR-39, Protegrin-1, and 18s rRNA were designed respectively according to theknown porcine antibacterial peptides and 18s-rRNA gene sequences to detect themRNA expression of antibacterial peptide genes by an optimized semi-quantitativeRT-PCR. The purpose was to provide theoretical support and guidance for thedevelopment and application of environment protection type feed additives in thefuture, which woud become the substitute of antibiotics.Experiment 1: Total twenty-eight with the same embryo, similar body weight andhealthy male piglets (Duroc×(Landrace×Yorkshine)) to seven groups, each group offour pigs at 0, 3, 14, 23 (2 days after weaning), 28 (not Weaning), 28 (7 days afterweaning) days-age were slaughtered and sampled thymus gland, spleen, lymphonodimesosteniales and bone marrow respectively under the asepsis condition, in which thedifferences between the gene expression of PR-39 and Protegrin-1 and the effect ofweaning were detected by means of RT-PCR. The results showed that, the levels ofPR-39 and Protegrin-1 mRNA expression in the bone marrow were the most(P＜0.05),thymus the second, spleen and lymphonodi mesosteniales the last. And the variationregularities of PR-39 expression with days-age were well coincident in differentimmunity tissues: the levels of PR-39 mRNA expression tended to be increased at the0～3 d and reduced at the 3～14 d, but increased at the 14～28 d again. The levels ofProtegrin-1 mRNA expression in the bone marrow and thymus gland were increasedpersistingly with days-age, but the statistic result was not significant among differentdays-age. The rules of mRNA expression were identical between Protegrin-1 andPR-39 in the spleen and lymphonodi mesosteniales. In addition, compared with the 23d (not weaning), the gene expression of PR-39 and Protegrin-1 in each immune tissuetended to be reduced at the 23 d (2 days after weaning), it was reduced by 16.04% (P＜0.05) and 20.11% (P＜0.05) respectively in the bone marrow, but there wereinsignificant differences in thymus gland, spleen and lymphonodi mesosteniales. Thegene expression of PR-39 and Protegrin-1 in each immune tissue at the 28 d (7 daysafter weaning) tended to be reduced compared with the 28 d (not weaning), but thedifferences were not significant. The results revealed that differences of the geneexpression of PR-39 and Protegrin-1 existed with different immune tissues anddays-age, and weaning caused a significant effect to its gene expression.Experiment 2. 160 weaning pigs (Duroc×(Landrace×Yorkshine)) of 28d withsimilar body weight were randomly allotted to five treatments with four replicateseach and of eight weaning pigs. The pigs were fed five different dietary respectively:the basal dietary (DE 13.50MJ/k g, CP 18.60% ), the diet supplemented with 0.027%antibiotics, 0.05% polysaccharides compound (Achyranthes bidentata, CodonopsisPilosula, Eucommia bark), 0.10% polysaccharides compound and 0.15%polysaccharides compound. The pre-feeding period was 7d, the feeding period was28d. When the feeding experiment was finished, each treatment of four pigs wereslaughtered and sampled bone marrow of left thighbone under asepsis condition, inwhich the mRNA expression of PR-39 and Protegrin-1 were detected. The resultsshowed that the effects of adding polysaccharides compound to the diet on PR-39 andProtegrin-1 mRNA expression were significant. The mRNA expression of PR-39 andProtegrin-1 could be promoted to a different extent with different dose ofpolysaccharides compound in weaning piglets, especially the adding 0.10%polysaccharides compound group. Compared with the control group and theantibiotics group, in 0.10% polysaccharides compound group, the expression level ofPR-39 was markedly increased by 50% and 51.5% (P＜0.05) respectively, and theexpression level of Protegrin-1 was increased by 36.36% (P＜0.05) and 27.90%(P＞0.05) respectively, but statistic result was not significant among thepolysaccharides compound groups.
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