【作者】 李武林；

【导师】 姚军虎； 杨小军；

【作者基本信息】 西北农林科技大学 ， 动物营养与饲料科学， 2010， 硕士

【摘要】 本文系统研究了不同免疫应激状态下肉鸡生产性能、养分消化、血液生化、肌肉品质、免疫功能及肠道微生物区系的变化规律,为从健康与营养角度探讨免疫应激与养分重分配的机理,优化肉鸡免疫程序提供理论依据。按照单因子试验设计,选用540只1日龄Cobb500肉鸡随机分为5个处理,每处理9重复,每重复12只。试验分为无免、简化免疫、常规免疫、免疫亢进和免疫抑制5个处理组。试验一免疫应激对肉鸡生长性能、养分消化和肌肉品质的影响结果显示,不同免疫应激对肉鸡料重比无显著影响(P>0.05),LPS亢进和CPM免疫抑制均显著降低肉仔鸡的体增重和采食量(P<0.05);免疫应激对能量表观消化率无显著影响(P>0.05),应激显著降低了DM和EE的表观消化率(P<0.05)。CPM抑制降低了日粮CP回肠表观消化率(P<0.05),简免、常免和CPM抑制组日粮CP表观消化率均有升高的趋势(P<0.01);CPM抑制显著增大了肌肉滴水损失(P<0.01)。结果表明:合理控制饲养环境条件下,无免疫不影响肉鸡生产性能,而免疫应激会降低肉鸡对日粮DM、CP、EE的消化率,影响采食量和体增重,不利于肉鸡生长和生产。试验二免疫应激对肉鸡免疫功能及相关免疫参数的影响结果显示,不同免疫应激对42 d肉鸡外周血白细胞、淋巴细胞、粒细胞数量及G/L比值无显著影响(P>0.05);与对照组相比,LPS亢进显著增大了肉鸡脾脏指数(P<0.01),CPM抑制显著降低了肉鸡法氏囊指数(P<0.01);LPS亢进组和CPM抑制组均降低了肉鸡肠道分泌型IgA的水平(P<0.01)。LPS亢进组42 d龄血清IgG比无免、简免和常免组显著升高(P<0.01)。不同免疫应激对后期肉鸡外周血B淋巴细胞转化率无显著影(P>0.05)。前期表现为亢进组显著增高(P<0.05),抑制组有降低趋势;26 d时,常免和亢进组ND抗体HI效价显著高于无免组(P<0.05)。LPS亢进组和CPM抑制组血清溶菌酶较无免组有降低的趋势(P>0.05)。结果表明:无免疫和简化免疫增强了肉鸡粘膜免疫机能。本试验LPS注射激活了体液免疫应答。CPM注射抑制了法氏囊的发育,主要抑制细胞免疫应答反应。试验三不同免疫应激状态下肉鸡盲肠消化与微生物区系的关系结果显示,本试验反应体系和扩增条件下ERIC检测结果稳定性和重复性均较好。ERIC-PCR扩增产物大部分均为500~3000bp大小的基因片段;盲肠菌群图谱聚类结果显示,21 d龄LPS亢进组与无免组相比盲肠菌群DNA指纹图谱特异性较高,CPM抑制组在76%遗传相似度的基础上具特异性指纹图谱。42 d龄CPM抑制组、简免组和常免组与无免组相比盲肠菌群DNA指纹图谱特异性均较高,而LPS亢进组图谱特异性不明显。常免组、LPS亢进组和CPM抑制组盲肠CP消化率呈降低的趋势,且后期差异极显著(P<0.01)。结果表明:不同免疫应激状态下肠道菌群结构变化明显,检测肠道菌群结构变化可用于评判肉鸡免疫应激水平。肉鸡在免疫应激状态下,排泄物中CP含量受盲肠微生物影响较大,故通过检测粪中CP表观消化率来反映饲料CP利用率准确度下降。综上所述,合理控制饲养环境,对肉鸡不免疫或简化免疫可达到与常规免疫相同的生产性能。免疫应激改变了肠道菌群结构,降低肠道粘膜免疫机能,影响体液和细胞免疫应答,降低肉鸡对日粮消化率从而影响肉鸡生长。更多还原

【Abstract】 Three trials were conducted to determine the effect of different immune stress on growth performance, nutrient metabolism, serum biochemical parameters, meat quality, immunity and cecal microflora in broiler chickens. Five hundred and forty Cobb500 broilers aged 1 day were randomly assigned to 5 groups with 9 replicates per group and 12 birds each replicate (Group 1: control group without experimental stress, Group 2: stress from simplified vaccination, Group 3: stress from general vaccination, Group 4: stress from LPS injection and general vaccination, Group 5: stress from CPM injection and general vaccination).Trial 1 was to evaluate on the effects of different immune stress on growth performance, nutrient metabolism, serum biochemical parameters, and meat quality in broilers. The results showed that feed conversion ratio and apparent digestibility of energy had no significant difference among 5 groups (P>0.05). Average body weight, apparent digestibility of dry matter and crude fat decreased significantly after treatment with LPS and CPM (P<0.05). Apparent ileal digestibility of crude protein of group 5 was lower than the control group (P<0.05), however, the drip loss of group 5 was higher than the control group (P<0.01). The apparent digestibility of crude protein increased in group 2, 3 and 5 (P<0.05). These data suggest that there were no adverse effects on growth performance of broilers without vaccination in the conditions of controlling rational feeding environment. However, excessive immune stress goes against the apparent digestibility of DM, EE, CP and the growth performance of broilers.Trial 2 aimed to study the effects of different immune stress on immunity and immunological parameters in boilers. The results showed that compared with group 1, the levels of secreted IgA decreased significantly after treated with LPS and CPM on 42 days (P<0.01). The spleen index, proliferation of B Lymphocyte, levels of 42 days’serum IgG and titers of 26 days’ND antibody of group 4 were higher than the control group (P<0.05), furthermore, the index of bursa of fabricius of group 5 was lower than the control group (P<0.01). There were no significant difference on the amount of leukocyte and lymphocyte cell, the granulocyte to lymphocyte ratio in blood and the serum lysozyme activity among 5 groups (P>0.05). In conclusion, Immune stress had adverse effects on mucosal immune function of broilers. Experimental model of immune stress was established, however, experimental model of immunosuppression failed to decrease humoral immune response.Trial 3 was conducted to investigate the effects of different immune stress on cecal microflora in broilers. The results showed: the DNA fingerprinting of ERIC-PCR had high stability and good repetition. The molecular weights of gene fragment were almost 500 to 3000bp after ERIC-PCR amplification. The genetic similarity within bacterial populations in group 4 was higher than group 5 on 21 days. However, group 4 had lower genetic similarity with bacterial populations than group 5 on 42 days. Group 3, 4 and 5 had lower cecal digestibility of crude protein than the control group (P<0.01). In conclusion: Different immune stress influenced the structure of cecal bacterial. The DNA fingerprinting of ERIC-PCR reflects intestinal health and status of immune activation. The apparent digestibility of crude protein shows great variabilities in condition of immune stress.All the analysis shows that broilers with simplified vaccination or without vaccination can reach the same growth performance as broilers with general vaccination in the conditions of controlling rational feeding environment, while immune stress can break the homeostasis of cecal microflora structure, impair intestinal mucosal immune function, decrease humoral, cellular immune responses, result lower feed intake and body weight, finally inhibit growth of broiler chickens.更多还原