Effects Of Catalase Supplementation In Diet On Oxidative Stress And Its Mechanism In Yellow Broilers

Yellow broiler has the characteristics of delicious meat and its industry has developed rapidly in recent years.About 4-5 billion yellow broilers are put on the market every year.It plays an important role in the development of broiler industry and even the whole animal husbandry in China.Oxidative stress occurs when the animal’s body stimulated by adverse factors,reactives oxygen species and other free radicals are produced in large quantities,which exceeds the scavenging capacity of cells,and the oxidative system and antioxidant system lose balance.Reactive oxygen species and other free radicals damage DNA,protein and lipid molecules,resulting in tissue damage.Oxidative stress is an important factor to induce disease.In the process of breeding,many factors can result in oxidative stress,including rapid growth of broilers,high temperature,high density feeding,high concentration of nutrients,mycotoxins,oxidation and diseases,etc.As a result,the growth performance and immune function of broilers were reduced,and the mortality rate was increased,which caused huge economic loss to the chicken industry.Catalase（CAT）is the main enzyme in the body’s antioxidant defense system.Its function is to catalytic electron transfer,decompose the hydrogen peroxide（H₂O₂）inside the cells into water（H₂O）and oxygen（O₂）.In this way,reactive oxygen species and other free radicals induced by oxidative stress can be removed to reduce the damage to cells and play a protective role in cells.To study the effects of dietary catalase on growth performance,intestinal morphology and antioxidant performance of yellow broilers and the protective effect of catalase on oxidative stress of yellow broilers is of great significance for improving the breeding efficiency of yellow broilers and promoting the development of the industry.In this study,four experiments were conducted to investigate the effects of catalase supplementation on growth performance,intestinal morphology and antioxidant performance of yellow broilers under normal and oxidative stress conditions,as well as the possible mechanism of its protective effect on oxidative stress.The aim of this study was to provide a theoretical basis and a new idea for alleviating oxidative stress in yellow broilers by applying exogenous enzymes as nutritional regulation means.The main contents and results of the study are as follows:1)Effects of different supplemental levels of catalase on growth performance,intestinal morphology and antioxidant performance of yellow-feathered broilersA total of 360 one-day-old male healthy Lingnan yellow broilers from the same source were selected and randomly divided into 4 treatment groups（0,200,300 and 400 mg/kg basal diet）with 6 replicates per group and 15 broilers per replicate according to catalase supplemental level.The experiment lasted for 30 days.The effects of different supplemental levels of catalase on growth performance,intestinal morphology and antioxidant capacity were investigated.The experimental results showed as follows:Adding 300 and 400 mg/kg catalase significantly increased ADG（15.86%and 22.74%）,and significantly decreased（P<0.05）the ratio of feed intake to weight gain（13.00%and 15.50%）of yellow broilers（P<0.05）.The activities of SOD,GSH-Px and CAT in the serum were markedly increased（P<0.05）,the total antioxidant capacity in the serum and liver was markedly increased（P<0.05）,and the content of malondialdehyde（MDA）in the serum was memorably decreased（P<0.05）.Villus height and the ratio of villus height to crypt depth in the jejunum and ileum were significantly increased（P<0.05）,while crypt depth was memorably decreased（P<0.05）.Comprehensive comparison and analysis of the data of the four experimental groups showed that the effect of adding 400 mg/kg catalase group was the best under the conditions of this experiment.2)Effects of catalase on growth performance,intestinal morphology and antioxidant performance of yellow-feathered broilers at different stagesA total of 360 one-day-old male healthy Lingnan yellow broilers with similar body weight were selected and randomly divided into three groups:control group（CON）（fed with basic diet）,300 mg/kg CAT group（fed with basic diet+300 mg/kg catalase）and 400 mg/kg CAT group（fed with basic diet+400 mg/kg catalase）.Each group had 8 replicates and 15chickens in each replicate.The experiment was divided into two stages:early stage（day1-30）and late stage（day 31-60）,to determine the effects of catalase on growth performance,intestinal morphology,antioxidant performance and intestinal microbial composition of yellow broilers at different stages.The results showed as follows:1)In the early stage,adding 400 mg/kg catalase significantly increased ADG（17.31%）（P<0.05）,and significantly decreased the ratio of feed to gain（14.29%）（P<0.05）.The activities of CAT and GSH-Px in the liver and serum and CAT in the jejunum were significantly increased（P<0.05）,and the total antioxidant capacity（T-AOC）of the liver was significantly increased（P<0.05）.Villus height and ratio of villus height to crypt depth in the duodenum,jejunum and ileum were significantly increased（P<0.05）,while crypt depth of them were significantly decreased（P<0.05）.Firmicutes,Bacteroidetes and lactobacillus in the jejunum were significantly increased（P<0.05）,and bacteroidetes and total bacteria in the cecum were significantly increased（P<0.05）,while Escherichia coli was significantly decreased（P<0.05）.The m RNA relative expression levels of JAM2,MUC2,Occludin,in the duodenum,and Occludin in the jejunum,and JAM2,Occludin in the ileum were significantly up-regulated（P<0.05）.2)In the later stage,ADG was increased by 7.12%and the ratio of feed to gain was decreased by 6.41%,but the differences were not significant（P>0.05）.The activities of SOD and GSH-Px in the liver,and CAT and GSH-Px in the serum and CAT in the jejunum were significantly increased（P<0.05）,and the total antioxidant capacity（T-AOC）in the liver and serum were significantly increased（P<0.05）.Villus height and the ratio of villus height to crypt depth in the duodenum and jejunum,and the ratio of villus height to crypt depth in the ileum were significantly increased（P<0.05）,while the crypt depth of the duodenum and ileum was significantly decreased（P<0.05）.The m RNA relative expression levels of MUC2 in the duodenum,JAM2,MUC2,Occludin,ZO-1 in the jejunum,JAM2,MUC2,Occludin in the ileum were significantly up-regulated（P<0.05）.In summary,dietary catalase supplementation can improve the growth performance,and intestinal morphology and antioxidant capacity of yellow broilers,the improvement effect on growth performance was better in the early stage than in the late stage.3)Effects of catalase on growth performance,intestinal morphology,antioxidant performance and immune capacity of yellow broilers under Diquat-induced oxidative stressA total of 480 seven-day-old male healthy Lingnan yellow broilers with similar body weight were randomly divided into 4 treatment groups with 8 replicates per group and 15broilers per replicate.Two treatment groups fed basal diet,while the other two fed basal diet added with CAT 400mg/kg.The experiment lasted for 21 days.On the 14th day of the experiment,one treatment group of basal diet and one group of basal diet added wtih CAT400 mg/kg were randomly selected for a one-time intraperitoneal injection of 25 mg/m L diquat solution at 10 mg/kg.BW and the other two groups were given a one-time intraperitoneal injection of the same dose of sterilized saline.To investigate the effects of catalase on growth performance,intestinal morphology,antioxidant performance and immune capacity of yellow broilers under oxidative stress.The test results showed that dietary catalase supplementation significantly alleviated（P<0.05）the decrease of ADG and ADFI and the increase of the ratio of feed to gain caused by diquat intraperitoneal injection.The activities of T-AOC and SOD,GSH-Px and CAT in the liver,serum and jejunum induced by intraperitonael injection were significantly increased（P<0.05）,while the content of MDA in the liver,serum and jejunum was significantly decreased（P<0.05）.The contents of Ig A,Ig G and Ig M in the serum and Ig G in the jejunum after diquat intraperitoneal injection were significantly increased（P<0.05）,while the content of sicam-1 in jejunum was significantly decreased（P<0.05）.The bursa of Fabricius index and the ratio of CD4+to CD8+in the serum induced by intraperitonael injection were significantly increased（P<0.05）after diquat intraperitoneal injection,and the proportion of CD8+in serum was significantly decreased（P<0.05）.Villus height and the ratio of villus height to crypt depth in the duodenum,jejunum and ileum after diquat intraperitoneal injection were significantly increased（P<0.05）,and crypt depth of duodenum,jejunum and ileum was significantly decreased（P<0.05）.The contents of IL-1β,IL-6,IL-8 and TNF-αin the liver,serum and jejunum after diquat intraperitoneal injection were significantly decreased（P<0.05）.There were interaction effects in the ratio of feed to gain,the level of T-AOC in the liver,the contents of IL-1βand IL-6 in the serum,the contents of IL-1β,IL-6 and TNF-αin the jejunum between the supplementation of CAT and diquat intraperitoneal injection.4)Mechanism of catalase alleviating oxidative stress induced by Diquat in yellow broilersOne chicken was randomly selected from each replicate of test 3 to slaughter,and some liver and intestinal tissues were taken to measure the expression levels of NF-KB signaling pathway,Nrf2-Keap1 signaling pathway and intestinal tight junction related genes.The aim of this study was to investigate the protective mechanism of catalase against oxidative stress.The results showed as follows:1)Catalase supplementation significantly up-regulated the gene expression of SOD,GSH-Px and CAT in the liver and serum induced by diquat intraperitoneal injection（P<0.05）,and significantly down-regulated the gene expression of Nrf2 in the liver and jejunum（P<0.05）.2)The expressions of NF-кB,COX-2 and My D88 in the liver and jejunum after diquat intraperitoneal injection were significantly down-regulated（P<0.05）.3)The down-regulation of gene expression of Occludin,Claudin and ZO-1 in the duodenum,jejunum and ileum caused by diquat intraperitoneal injection were significantly alleviated（P<0.05）.4)There were interaction effects on the expression of NF-кB in the liver,NF-кB,My D88 and GSH-Px in the jejunum between CAT supplementation and diquat intraperitoneal injection.In conclusion,dietary catalase supplementation can improve the growth performance and antioxidant capacity of yellow broilers under normal conditions and oxidative stress conditions,ameliorate the intestinal structure,enhance the barrier function of the intestinal epithelium,improve the body’s immunity and anti-inflammation capacity,restore the damage of oxidative stress.The protective mechanism of catalase against oxidative stress is related to the regulation of the NF-κB signaling pathway,the Nrf2-Keap1 signaling pathway and the expression of intestinal tight junction related genes.