Treatments in a 2x2 arrangement were A: Og/d-head rumen protected Met, Og/d-head nicotinic acid;

• 采用2×2因子(过瘤胃蛋氨酸×烟酸)安排的4×4拉丁方试验设计,在奶牛基础日粮中分别加入:A 0g/d·head过瘤胃蛋氨酸+0g/d·head烟酸;