The USDA pays a certain amount of money for each name/address of a person who owns/keeps livestock and/or poultry. They then add it to their database, the first step in tracking and monitoring farms, breeders, private citizens and others who have animals.
Each state's agriculture department has access to these names/addresses since every municipality is required to do an annual census of all livestock and poultry, and certain exotic animals/birds as well. However, it is illegal for them to disclose the information unless/until the state's governor-appointed council of senators votes to accept NAIS.
These censuses -- sometimes called a "barn book" -- are typically taken by the municipality's animal control officer or dog officer, who then sends the list to his/her state's ag office. Here in Massachusetts it's the Mass. Dept. of Agricultural Resources, the director of which is Douglas Gillespie. Not many years ago, Gillespie illegally sent the barn book to the USDA and collected the price-per-head for each livestock/poultry owner's name and address. The money was given to the state, as far as I know, but it was still an illegal action since Massachusetts had not (and still has not) voted to accept NAIS regulation from the USDA.