Objective To prepare directional and sustained-released IgY microcapsules and evaluate its effect. Methods IgY microcapsules against diarrhea in piglets were prepared by sparay drying technique using gelatin and sodium alginate as the wall materials. An L_9(3_4)orthogonal experiment was performed to optimize the technological condition for preparation of the microcapsules based on the effect of formula of materials on the performance of microcapsules, the influencing factors of stability of encysted emulsio...