The Federal government provides regulations for food product and nutrition labeling which you, as the producer or manufacturer, are responsible for adhering to. The FDA of the DHHS is the Federal agency responsible for the majority of food products and their labeling. The USDA is responsible for fresh meat, poultry and eggs.
Neither department provides nutrient analysis or creates the Nutrition Facts label for a product. As the producer or manufacturer, you may select any company or entity to do your analysis and create your Nutrition Facts label, provided they follow the Federal regulations.
You may also first want to check the Small Business Nutrition Labeling Exemption (link is external). The FDA provides food labeling guidance for food producers and manufacturers, including the Food Labeling Guide (link is external). Also available is Guidance for Industry: Nutrition Labeling Manual - A Guide for Developing and Using Data Bases (link is external).