Sixteen sows (Tianjing White) were randomly allotted to one of three dietary treatments with six pens per treatment and one sow per pen according to the initial weight and parity.

• 选用分娩日期相近的天津白猪18头,按胎次、体重随机分成3个处理组,每个处理6个重复,每个重复1头母猪。