Section 36G. If any animal tested by an approved licensed veterinarian designated by the director under this section reacts positively to an approved blood test for brucellosis and is slaughtered in consequence thereof, or if any animal does not react positively but has been exposed to brucellosis in an infected herd, said animal may be slaughtered because of such exposure to the positive reactors in accordance with the recommended uniform methods and rules published by the veterinary services of the animal and plant health inspection service of the United States Department of Agriculture. The director may appoint persons to make appraisals of reacting cattle in conjunction with the owner or his authorized representative. Such appraisal shall be subject to the rights of arbitration and petition set forth in section thirty-one; provided, that the award or damage shall be within the limits prescribed by this section. The commonwealth, shall within thirty days after the filing in the office of the director of a valid claim for reimbursement in pursuance of such an appraisal or award under said section thirty-one, pay to the owner of any animal slaughtered under authority of any rules and regulations made hereunder, or to any mortgagee or assignee designated in writing by said owner, two thirds of any difference between the amount received by the owner for the carcass of the animal and the value of the animal as determined by appraisal as aforesaid; provided, that payment by the commonwealth hereunder shall not exceed one hundred and fifty dollars for any grade animal or two hundred dollars for any purebred animal; and provided, further, that no payment shall be made for any such animal unless it was kept by the owner applying for the test on the premises where tested for at least sixty days next prior to the date of said test, or unless it was admitted to the herd on a test approved by the director and provided, further, that no payment shall be made for any animal if, since a previous test, the owner or his representative has violated the rules and regulations made hereunder; and provided, further, that the owner or his representative has not unlawfully or improperly obtained or attempted to obtain reimbursement for any animal; and provided, further, that the owner or his representative has not, in the opinion of the director, by wilful act or neglect, contributed to the spread of bovine brucellosis. If the federal government pays part of the value of any animal slaughtered under this section, the payment by the commonwealth shall be limited to the difference between the payment authorized by the federal government and the payment as hereinbefore provided.