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