甘草酸对脂多糖应激黄羽肉仔鸡免疫性能的影响

【目的】 本试验旨在研究甘草酸（GA）对黄羽肉仔鸡免疫性能的影响。【方法】 选取300只体重接近的1日龄健康黄羽肉仔鸡，随机分为6组，每组5个重复，每个重复10只，分别为空白对照组、脂多糖处理组（LPS组）、黄芪多糖组（APS组）、高剂量甘草酸组（GA_H组）、中剂量甘草酸组（GA_M组）和低剂量甘草酸组（GA_L组）。空白对照组于14、16、18、20日龄早上腹腔注射0.9%无菌生理盐水2 mL，其余各组同时间注射等量的LPS溶液（1.5 mg/kg BW）建立体内免疫应激模型。空白对照组和LPS组饲喂基础饲粮，APS组、GA_H、GA_M和GA_L组于应激模型建立阶段及前后3 d （即11~23 d）分别在基础饲粮基础上添加400 mg/kg黄芪多糖（APS）和120、100、80 mg/kg的GA；试验期49 d。在21、28、35、42、49日龄每个重复随机选取2只鸡采集翅静脉血，用酶联免疫法（ELISA）测定血清中CD4、CD8分子含量及免疫活性物质IgA、IgG、IgM含量。【结果】 与空白对照组相比，21~49日龄时，其余5组肉仔鸡血清CD4分子含量均极显著下降（P<0.01），而血清CD8分子、IgA、IgG、IgM （除GA_H组和APS组外）含量均有所升高。与LPS组相比，APS组和3个GA组肉仔鸡血清CD4分子含量均有所升高，而血清CD8分子含量均极显著或显著降低（P<0.01；P<0.05），血清IgA、IgG、IgM含量均极显著降低（P<0.01）。此外，在3个GA组间，肉仔鸡血清CD4分子含量均随GA添加量增加而升高，其中GA_H组的升高幅度与APS组最接近，尤其是在42日龄时，GA_H组与APS组间差异不显著（P>0.05），且均极显著或显著高于LPS组（P<0.01；P<0.05）；而肉仔鸡血清CD8分子、IgA、IgG、IgM含量随GA添加量增加呈降低趋势，其中GA_H组的降低幅度与APS组最接近，在CD8分子含量方面，两组间无显著差异（P>0.05），且在35和49日龄时，GA_H组肉仔鸡CD8分子含量与空白对照组差异不显著（P>0.05）；在IgA含量方面，除35日龄外，其他日龄时GA_H组与APS组间均无显著差异（P>0.05），在21和49日龄时，GA_H组与空白对照组差异均不显著（P>0.05）；在IgG含量方面，除28日龄外，其他日龄时GA_H组与APS组间均无显著差异（P>0.05），在35日龄时，GA_H组与空白对照组差异不显著（P>0.05）；在IgM含量方面，除42日龄外，其他日龄时GA_H组与APS组间均无显著差异（P>0.05），在21日龄时，GA_H组与空白对照组差异不显著（P>0.05）。【结论】 GA能有效缓解黄羽肉仔鸡对LPS刺激引起的免疫应激反应，增强免疫调节能力，且与保护效果之间有剂量效应，由强到弱依次为GA_H>GA_M>GA_L。

Effects of Glycyrrhizic Acid on Immune Performance of Lipopolysaccharide-stressed Yellow Feather Broilers

【Objective】 This experiment was conducted to investigate the effect of glycyrrhizic acid(GA) on the immune function of Yellow-feathered broilers.【Method】 A total of 300 one-day-old healthy Yellow-feathered broiler chickens with similar body weight were selected and randomly divided into 6 groups, with 5 replicates in each group, 10 in each replicate, namely the normal saline group (NS), lipopolysaccharide (LPS) group, astragalus polysaccharide group(APS), high-dose glycyrrhizic acid group(GA_H), middle-dose glycyrrhizic acid group(GA_M) and low-dose glycyrrhizic acid group(GA_L).The NS group was intraperitoneally injected with 2 mL of 0.9% sterile saline in the morning of 14, 16, 18 and 20 days old, and the other groups were injected with an equal volume of LPS solution (1.5 mg/kg BW) at the same time to establish immune stress model in vivo. NS group and LPS group were fed with the basal diet, while APS group, GA_H, GA_M and GA_L experimental groups were supplemented with 400 mg/kg astragalus polysaccharides (APS) and 120, 100, 80 mg/kg of GA on the basis of the basal diet at the stage of establishment of the stress model and 3 days before and after the stage (11-23 days).The experimental period was 49 days.At 21, 28, 35, 42 and 49 days of age, 2 chickens were randomly selected in each replicate to collect wing vein blood, and the contents of CD4, CD8 and immunological active material IgA, IgG and IgM in serum were determined by enzyme-linked immunosorbent assay (ELISA).【Result】 Compared with NS group, at the age of 21-49 days, the serum CD4 molecule content of the other 5 groups of broilers was extremely significantly decreased (P<0.01), while the serum CD8 molecule, IgA, IgG, IgM (except GA_H group and APS group) were increased.Compared with LPS group, the serum CD4 molecular contents of broilers in APS group and three GA groups were increased, while the serum CD8 molecular contents were extremely significantly or significantly decreased (P<0.01;P<0.05).The serum IgA, IgG and IgM contents were extremely significantly decreased (P<0.01).In addition, among the three GA groups, the serum CD4 content of broilers was increased with the increase of GA supplementation, and the increase in the GA_H group was the closest to that in the APS group, especially at 42 days of age, there was no significant difference between GA_H group and APS group (P>0.05), and all were extremely significantly or significantly higher than those in the LPS group (P<0.01;P<0.05)。However, the serum CD8, IgA, IgG, and IgM contents of broilers showed a decreasing trend with the increase of GA supplementation, and the decrease in GA_H group was the closest to that in APS group.There was no significant difference in CD8 molecular content between the two groups (P>0.05), and at 35 and 49 days of age, there was no significant difference in CD8 molecular content between GA_H group and NS group (P>0.05).In terms of IgA content, there was no significant difference between GA_H group and APS group except at 35 days of age (P>0.05), and at 21 and 49 days of age, there was no significant difference between GA_H group and NS group (P>0.05).In terms of IgG content, there was no significant difference between GA_H group and APS group except at the age of 28 days (P>0.05), and at the age of 35 days, there was no significant difference between GA_H group and NS group (P>0.05).In terms of IgM content, except for 42 days, there was no significant difference between GA_H group and APS group at other days (P>0.05).At 21 days, there was no significant difference between GA_H group and NS group (P>0.05).【Conclusion】 GA could effectively relieve the immune stress response of Yellow feather broiler chickens induced by LPS stimulation, and enhance the immune regulation ability.