At 7, 14, 21, 24 and 35 days of age, one piglet every litter was slaughtered, and tissues of stomach bottom, duodenal intestine and jejunal intestine were collected for histological analysis.

• 于仔猪7、14、21、24、35日龄每窝屠宰一头，取胃底、十二指肠、空肠组织进行组织形态学观察。