If it appears that any provisions of this act have been violated, the secretary shall certify the facts to the proper prosecuting attorney and furnish that officer with a copy of the result of the analysis or other examination of such feeding stuffs duly authenticated by the analyst or other officer making the determination, under the oath of such officer. If it shall appear from any such examination that any provisions of this act have been violated, the secretary shall cause notice to be given to the manufacturer or dealer from whom the sample was taken; any party so notified shall be given an opportunity to be heard in defense under such rules and regulations as may be prescribed by the secretary of agriculture before the facts shall be certified to the proper prosecuting attorney. In all prosecutions arising under the provisions of this act, certificates of the analyst making the analysis, when duly sworn to by such analyst shall be prima facie evidence of the fact or facts therein certified.