Weights and measures, which conform to the standards of the United States national institute of standards and technology existing as of January 1, 1979, that are traceable to the United States standards supplied by the federal government or approved as being in compliance with its standards by the national bureau of standards shall be the state primary standard of weights and measures. Such weights and measures shall be verified upon initial receipt of same and as often as deemed necessary by the secretary of agriculture. The secretary may provide for the alteration in the state primary standard of weights and measures in order to maintain traceability with the standard of the United States national institute of standards and technology. All such alterations shall be made pursuant to rules promulgated by the secretary in accordance with chapter 17A.