Effects Of Dietary Vitamin A Supplementation Level And Stress On Mucosal Immune Of Respiratory Tract In Broilers

The purpose of this research is to study the effects of different vitamin A supplementation on respiratory tract mucosal immunity under the immunological stress of LPS and NH3 in broilers, provided a theoretical basis for confirming the mechanism of vitamin A in the maintenance of mucosal integrity. Experiments studied dietary vitamin A can indeed affect mucosal immune function firstly, and then investigated LPS play a role in immunological stress. Finally we researched and detected the effects of vitamin A on mucosal immunity fuction the presence of LPS and NH3.Trial 1, according to the diet vitamin A gradient, 1 day old AA broilers were divided into 4 treatments: 0IU/kg, 1500IU/kg, 6000IU/kg, and 12000IU/kg. Feed and water were provided ad libitum for 7 days. Results: the effect of different vitamin A addition on serum Ig A as well as BALF IgA and mucin concentration has a significant difference. When vitamin A supplement is 0 or lower, it will inhibit production of goblet cells, Ig A and mucin. And the gene expression of cytokines such as TNF-α, TGF-α, EGFR, IL-13, TGF-β also has a significant difference. Therefore, reserch proved: vitamin A indeed involves in the regulation of respiratory tract mucosal immune, and may be regulated production of Ig A and mucin by influencing gene expression of cytokines.Trial 2, we selected 7 day old AA broilers, LPS atomized at 1mg/kg dose of chicken weigh in experimental group. Saline atomized with the same volume of control group. The chickens exposed for 2 hours. Sample after 4h and 8h. Results: LPS inhibited mucus production in BALF, caused the concentration of Ig A in serum and BALF showing a rising trend, and increased the protein expression of IgA in lung tissue. Therefore, results proved: LPS can stimulated mucosal immune stress reaction of respiratory tract.Trial 3, according to the results of trial 1 and trial 2, combined with NH3 being one of the most important factors that induce respiratory diseases of poultry in the process of production. Simulated immune stress by LPS and NH3, at the same time, supplemented vitamin A to research the effects of vitamin A, LPS and NH3 on respiratory tract mucosal immunity in broilers. According to the vitamin A levels of diet, 1 day old AA broilers were divided into 1500IU/kg and 6000IU/kg. At the age of 14 days, broilers were treated with exposuring to LPS(1mg/kg) and NH3(100ppm) for 2h. Sample after 4h. The results showed that: SEM showed NH3 and LPS treatment stimulate airway epithelial cilia sparse. Double stimulation of NH3 and LPS caused severe cilia sparse and epithelial cell damaged in a large area. Dietary vitamin A supplement can alleviate the cilia shedding in small area. In addition, the effect of diet and NH3 on the level of serum Ig A, BALF mucin concentration and pulmonary TNF-α, TGF-α, TGF-β mRNA expression level had interaction. There is also interaction in effect of diet and LPS on BALF mucin concentrations, lung IgA protein expression and EGFR mRNA.expression.The research showed that: vitamin A can regulate the production of Ig A and mucin, thereby affecting the immune function of respiratory tract mucosa. There is some interaction between vitamin A and LPS/ NH3 in the regulation of mucosal immunity. And vitamin A may be alleviate the stress effect of LPS/ NH3 on the respiratory tract by affecting the gene expression of cytokines, but the specific mechanism still needs further research; Vitamin A has the potential to alleviate respiratory diseases of the broilers, which has a certain guiding function for AA broilers production in our country.