510 ILCS 30/6.4: Female cattle of the beef breeds 18 months of age or older.

Female cattle of the beef breeds 18 months of age and over, for feeding and grazing purposes only, may enter the State, provided that such cattle are accompanied by an official certificate of health which states they were negative to an official test for brucellosis within 30 days prior to date of entry, which test shall be conducted by a State or Federal approved laboratory, or are under 24 months of age and were officially calfhood vaccinated.