All certificates of veterinary inspection required under the provisions of this chapter must be issued, and all tests must be made, by a federal or state veterinarian or a deputy state veterinarian, or by a graduate veterinarian whose inspections and tests are endorsed by the officer in charge of the state board of animal health work in the state where the inspection or test is made, and subject to the rules of the state board of animal health. All such tests must conform to the standard tests of the United States department of agriculture. All serums used must be manufactured or approved by the United States department of agriculture.