All laboratory tests of blood samples taken from cattle or other animals in certified brucellosis-free herds, cattle or other animals in cooperative herds in process of certification, additions to certified free and process herds, and all other animals on which an official test is required, including cattle or other animals intended for interstate shipment and exhibition at livestock fairs, expositions and shows, shall be made in the laboratory of the Idaho department of agriculture and such blood samples for official test may only be taken by persons approved by the department and the United States department of agriculture, veterinary services.