维生素D3除了维持动物体内钙磷平衡外，还依赖于维生素D受体，调节动物的免疫系统功能。本项目以我国重要经济鱼类-黄颡鱼为研究对象，系统研究低磷条件下，维生素D3调控鱼体抵抗病原入侵的首道防线-干扰素作用轴表达、鱼体经维生素D3营养调控后，抵御外界病原攻击的能力，以及鱼体免疫力与磷利用效率的关系。本项目将阐明干扰素作用轴基因被维生素D3影响的机制，探讨鱼类被维生素D3营养调控后，免疫力变化对提高饲料磷利用率的可行性，确定饲料中能增强鱼体抵御外源病原攻击的维生素D3合理添加水平，从而实现在不影响鱼体生长条件下，既能降低磷排放又能提高免疫力的饲料制作目标。本项目研究结果将能拓展维生素D在鱼类营养免疫领域的应用，利用维生素D的添加来降低养殖水体磷排放同时增强鱼体自身基础免疫能力。

In addition to its traditional function on maintaining calcium and phosphate homeostasis in animals, vitamin D3 can bind to vitamin D receptor and thus also regulates the immune responses. The current proposal intends to systematically study the effects of dietary vitamin D3 on interferon axis expression, which is the first line to resist the pathogens, the changes of the immunity when challenged by Edwardsiella, and the relationship between the immune response and phosphorus utilization in yellow catfish (Pelteobagrus fulvidraco). We try to clear the regulation mechanism of dietary vitamin D3 on fish interferon axis genes expression. We want to explore the possibility to improve dietary phosphorus utilization by enhancing fish immunity through dietary vitamin D3. The appropriate addition level of dietary vitamin D3 will be determined in order to enhance fish immunity to resist pathogens. The final target of this proposal is to make the feed formulation both to reduce phosphorus output and to enhance fish immunity without diminishing fish growth. The results from this project will expand the use of vitamin D in fish nutritional immunology and benefit the stakeholders in reducing phosphorus output as well as improving fish innate immunity.