Mo. Rev. Stat. § 267.525
Notwithstanding any provision in any of sections 267.470 to 267.550, the department shall allow and permit the owner of any animal which is found to be a reactor, to retain such animal in quarantine and use the animal for breeding purposes in his own herd, where necessary or desirable in order to preserve valuable breeding cattle; but the permission shall not be granted if the state veterinarian determines that the eradication program would be adversely affected and permission shall not be granted unless the United States Department of Agriculture agrees that county brucellosis status will not be affected. Such reactor animal may not be sold, transferred, or moved except on a special permit issued by the department.
(L. 1955 p. 5 § 267.320, A.L. 1973 S.B. 291)