id,birthdate,dam,sire,year,sex,weaning_weight
1,1/1/1990,,,1990,male,354
2,1/1/1990,,,1990,female,251
3,1/1/1991,,1,1991,male,327
4,1/1/1991,,1,1991,female,328
5,1/1/1991,2,1,1991,male,301
6,1/1/1991,2,,1991,female,270
7,1/1/1992,,,1992,male,330