Effect Of Vitamin A On Intestinal Barrier And Immune Function In Broilers Co-infected With Coccidia And Clostridium Perfringens

The purpose of this experiment was to investigate the effect of adding vitamin A（Vitamin A,VA）to the growth performance,intestinal barrier and immune function of broilers under the mixed infection of coccidia and Clostridium perfringens.This experiment is a random design of 2×2 factors.336 one-day-old white feather broilers（Rose 308）were selected and divided into 4 treatments based on the principle of similar body weight and random distribution,namely the addition of vitamin A（0 and 12000 IU/kg）And coccidiosis and Clostridium perfringens mixed infection treatment（infected and non-infected）,7 replicates per group,12 chickens per replicate（half male and female）.During the test period of42 days,the test was inoculated with coccidiosis vaccine d1（oral gavage,20-fold dose）to non-infected broilers and the same amount of normal saline.Inoculate the broiler with the required oral culture of Clostridium perfringens for 20 h at d18;the non-infected broilers should be inoculated with the same volume of sterile blisters without Clostridium perfringens but after the same treatment Base（1 m L/piece·day）,inoculated for 3 consecutive days.On the morning of the 28th and35th day of the experiment,they were starved for 8 hours before fasting and weighed.Blood was collected from the veins under the wings and slaughtered for sampling.1.The effect of vitamin A on the growth performance and intestinal damage of co-infected broilersThe results showed that:（1）Between d 1 and 14,there was no significant difference in feed intake between the groups（P>0.05）;compared with the blank group,the VA group significantly increased body weight gain（24.15 to 33.81%）and Significantly reduce the feed-to-meat ratio（14.94-23.13%）（P<0.05）.Compared with no VA addition,VA significantly increased broiler body weight gain（31.46%）and feed intake（32.25%）during d 15-21（during infection）（P<0.05）.VA significantly increased broiler feed intake（4.48%）（P<0.05）.（2）Compared with no addition of VA,VA significantly reduced the jejunal damage score of d 28（P<0.05）;compared with non-infection,the infection significantly increased the duodenal injury score of d 35（P<0.05）.VA decreased the intestinal injury scores;infection increased the d35 small intestine injury scores.Therefore,the addition of 12000 IU/kg vitamin A to the basic diet significantly improved broiler d 1-14 growth performance and small intestine injury score;coccidia and C.perfringens mixed infection can cause small intestine injury score.2.The effect of vitamin A on the intestinal barrier function of infected broilersThe results showed:（1）Compared with non-infection,the infection significantly increased the activity of plasma diamine oxidase at d 28（70.59%）（P<0.05）.（2）Compared with not adding VA,VA significantly increased d 28jejunum villi height and crypt depth value（P<0.05）,and significantly increased ileum villi height and villi height/crypt depth value（P<0.05）.VA had a decreasing interaction effect on the increase of d35 jejunum villi high index（P<0.05）.Compared with no addition of VA,VA significantly increased d 35 ileal villi height（P<0.05）.（3）Compared with not adding VA,VA has a significant effect on reducing the relative m RNA expression of d 28 jejunum claudin-1 gene（P<0.05）;but relative expression of m RNA of d 28 jejunum mucin-2 and d35 jejunum occludin genes The amount has a significant effect（P<0.05）.VA had an up-regulated interaction effect on the down-regulation of the relative m RNA expression of d35 jejunum mucin-2 gene by infection（P<0.05）.Therefore,the addition of 12000 IU/kg vitamin A in the basic diet can maintain the intestinal mucosal barrier function of broilers and improve the intestine caused by mixed infection by regulating the relative expression of the m RNA of the jejunum tight junction protein gene and improving the morphological structure of the small intestine.Tract injury.3.The effect of vitamin A on the immune function of infected broilersThe results show that:（1）VA has an increased interaction effect on the decrease of d 28 spleen index caused by infection（P<0.05）.Compared with not adding VA,VA significantly increased the d 35 spleen index（P<0.05）.（2）Compared with the non-infected group,the infected group significantly reduced the number of total T lymphocyte positive cells（CD₃⁺）in jejunal crypts d 28（P<0.05）,and significantly reduced the number of CD₃⁺cells in d 35 jejunal villi（P<0.05）.（3）Compared with non-infection,the infection significantly increased the content of Ig A in serum of d 28（P<0.05）.Compared with not adding VA,VA significantly reduced the Ig G content in serum of d 35（P<0.05）.VA has a significant up-regulation interaction effect on the down-regulation of d 35 serum Ig G content caused by infection（P<0.05）.（4）Compared with non-infection,the infection significantly increased the relative expression levels of IL-1βand IFN-γgene m RNA of d28spleen TGF-β4 and d35 spleen（P<0.05）.Compared with no VA addition,VA significantly reduced the relative m RNA expression of IL-10 gene in spleen of d28（P<0.05）.There was a significant up-regulated interaction effect of VA on the down-regulation of the relative expression level of IL-13 gene in d 35 spleen caused by infection（P<0.05）.（5）Compared with non-infection,infection significantly increased the relative expression level of d 28 jejunum IFN-γgene m RNA（P<0.05）.Compared with no VA addition,VA significantly reduced the relative m RNA expression of jejunum TGF-β4 and IL-8 genes at d 28（P<0.05）.Infection had a down-regulation interaction effect on VA-induced up-regulation of the m RNA expression of the d 35 jejunum IL-8 gene（P<0.05）.Therefore,adding 12000 IU/kg of vitamin A to the basic diet reduces the level of humoral immunity in the serum and regulates the relative expression of spleen and jejunum inflammatory factor m RNA,which is conducive to relieving the strong inflammation caused by infection..In summary,under the conditions of this experiment,mixed infection of coccidia and Clostridium perfringens caused an intestinal inflammatory reaction,which caused broiler growth performance and intestinal damage;the addition of vitamin A can significantly increase the growth of broilers before infection The performance can also improve the intestinal morphology and structure after infection,regulate the relative m RNA expression of jejunum mucin-2 and occludin,and reduce the serum immunoglobulin level,thereby alleviating the immune response and intestinal structure damage caused by infection.