Feds can compel any company that handles pre-pasteurized milk to share samples.
On Friday, the US Department of Agriculture (USDA) announced that it would begin a nationwide testing program for the presence of the H5N1 flu virus, also known as the bird flu. Testing will focus on pre-pasteurized milk at dairy processing facilities (pasteurization inactivates the virus), but the order that's launching the program will require anybody involved with milk production before then to provide samples to the USDA on request. That includes "any entity responsible for a dairy farm, bulk milk transporter, bulk milk transfer station, or dairy processing facility."
The ultimate goal is to identify individual herds where the virus is circulating and use the agency's existing powers to do contact tracing and restrict the movement of cattle, with the ultimate goal of eliminating the virus from US herds.