【作者】 李宁；

【导师】 魏凯；

【作者基本信息】 山东农业大学 ， 兽医（专业学位）， 2023， 硕士

【摘要】 热应激(Heat stress,HS)对家禽所带来的负面影响以及对养殖业造成的损失十分严重。热应激对畜禽造成的危害仍是当今养殖业所面临的重要问题,因此,开发更安全高效的抗热应激添加剂迫在眉睫。胆汁酸(Bile acids,BAs)作为胆汁的重要成分,在提高畜禽生产性能,缓解应激损伤,保障畜禽健康方面具有重要作用。目前猪胆汁酸应用较广,且对于热应激治疗效果明显,但对于与猪胆汁酸来源不同且在成分含量有所差异的羊胆汁酸是否具有相同效果尚不清楚。本研究从猪胆汁和羊胆汁中分别提取猪胆汁酸和羊胆汁酸,通过建立鸡热应激模型,运用分子生物学实验、血清学实验等,比较探究日粮中添加猪胆汁酸与羊胆汁酸对鸡的抗热应激效果。本研究旨在研制一种新的饲用营养保健添加剂并为改善家禽生产性能和预防家禽热应激提供实验基础和理论依据。主要研究内容和结果如下:本试验选取120只21日龄的海兰褐雏鸡随机分为4组:空白对照组(Mock)、热应激组(HS)、热应激-猪胆汁酸组(HS-porcine BAs)和热应激-羊胆汁酸组(HS-sheep BAs)。Mock组和HS组饲喂基础日粮,HS-porcine BAs组饲喂基础日粮+400 mg/kg猪胆汁酸,HS-sheep BAs组饲喂基础日粮+400 mg/kg羊胆汁酸,每日一次,连续饲喂7d。各组在第21 d、23 d、25 d、27 d四个时间点随机选取5只鸡进行体重称重,并于每天固定时间点测定采食量。于28日龄,将对照组继续饲养在常温条件下,其余各组置于生化培养箱,温度38±0.5℃,相对湿度60%,应激2 h。通过生化实验检测相关体内血清酶活性以及血清和组织内抗氧化能力,主要包括血清生化指标BUN、LDH、AST、ALT活性和氧化指标MDA、SOD、GSH的含量/活力。通过q PCR法检测肝脏以及空肠组织内HSP60、HSP70和HSP90,炎症因子IL-1β、TNF-α和IL-10,紧密连接蛋白(Occludin、ZO-1)m RNA表达量。运用ELISA方法检测空肠免疫指标SIg A变化情况。利用16S r RNA高通量测序技术分析鸡肠道菌群的变化。结果表明,热应激条件下,鸡血清中LDH、ALT含量升高,降低了血清、肝脏以及空肠组织内抗氧化水平,提高了组织内热休克蛋白和炎症因子的m RNA表达量,改变了空肠结构以及肠道SIg A含量,肠道中Firmicutes(厚壁菌门)相对丰度比例降低,Bacteroidota(拟杆菌门)相对丰度比例有所升高。日粮中添加两种BAs都可以提高鸡平均日增重以及饲料转化率,热应激条件下均可提高鸡抗氧化能力,降低肝脏以及空肠组织中热休克蛋白以及炎症因子的m RNA表达量,同时对改善空肠结构、粘膜屏障以及丰富肠道微生物区系有一定促进作用。相比而言,羊胆汁酸效果更显著。综上所述,日粮中添加羊胆汁酸对缓解鸡热应激损伤效果优于猪胆汁酸,提示羊胆汁酸作为一种新的饲用营养保健添加剂用于改善家禽生产性能和预防家禽热应激具有巨大潜力。更多还原

【Abstract】 The negative effects of heat stress(Heat stress,HS)on livestock and poultry and the losses caused by heat stress on the breeding industry are very serious.The harm caused by heat stress to livestock and poultry is still an important problem facing the breeding industry today.Therefore,it is urgent to develop more safe and efficient anti-heat stress additives.As an important component of bile,bile acid(Bile acids,BAs)plays an important role in improving the production performance of livestock and poultry,alleviating stress injury and ensuring the health of livestock and poultry.At present,porcine bile acid is widely used and has obvious therapeutic effect on heat stress,but it is not clear whether it has the same effect on sheep bile acid which is different from porcine bile acid and has different composition content.In this study,porcine bile acid and sheep bile acid were extracted from pig bile and sheep bile respectively.By establishing heat stress models in chickens,molecular biology experiments and serological experiments were used to compare the anti-heat stress effects of porcine bile acid and sheep bile acid in diet.The purpose of this study is to provide experimental and theoretical basis for the development of a new feed nutrition and health additive for improving poultry production performance and preventing heat stress in livestock and poultry.The main contents and results are as follows:In this experiment,21-day-old Highland brown chicks were randomly divided into 4groups: Mock group,HS group,HS-porcine BAs group and HS-sheep BAs group.Mock group and HS group were fed with basal diet,HS-porcine BAs group was fed with basal diet + 400mg/kg pig bile acid,and HS-sheep BAs group was fed with basic diet + 400 mg/kg sheep bile acid once a day for 7 days.Five chickens in each group were randomly selected and weighed at the four time points of 21 d,23 d,25 d and 27 d,and the feed intake was measured at a fixed time every day.At the age of 28 days,the control group was kept at normal temperature,and the other groups were placed in a biochemical incubator with a temperature of 38 ± 0.5 ℃,relative humidity of 60%,and stress for 2 hours.Biochemical experiments were used to detect the activity of serum enzymes and antioxidant capacity in serum and tissue,including the activity of serum biochemical indexes BUN,LDH,AST,ALT and the content / activity of oxidation indexes MDA,SOD and GSH.The m RNA expression of HSP60,HSP70 and HSP90,inflammatory factors IL-1β,TNF-α and IL-10,tight junction protein(Occludin,ZO-1)in liver and jejunum were detected by q PCR method.The ELISA method was used to detect the changes of jejunal immune index SIg A.The changes of intestinal microflora in chickens were analyzed by 16 S r RNA high-throughput sequencing.The results showed that under heat stress,the contents of LDH and ALT in serum increased,the levels of antioxidation in serum,liver and jejunum decreased,the m RNA expression of Heat shock proteins and inflammatory factors in jejunum increased,the structure of jejunum and the content of SIg A in intestine were changed,the relative abundance of Firmicutes decreased and the relative abundance of Bacteroidota increased in intestine.The addition of two kinds of BAs to the diet could increase the average daily gain and the feed conversion rate.Under heat stress,it could improve the antioxidant ability of chickens,reduce the expression of Heat shock proteins and inflammatory factor m RNA in liver and jejunum,and improve the structure of jejunum,mucosal barrier and enrich intestinal microflora.In comparison,the effect of sheep bile acid is more significant.To sum up,the effect of sheep bile acid in relieving heat stress injury in chickens is better than that in pigs,suggesting that sheep bile acid as a new feed nutrition and health additive has great potential to improve poultry production performance and prevent heat stress in poultry.更多还原