It would take quite a while to get the National Guard up to speed on processing meat in plants that would be efficient or up to safety standards.
You simply don’t take them, drop them in and hack away at carcasses.
I worked in a meat processing plant while in college. Training took a few minutes for any station. The work was easy. The management, though, was retarded and corrupt. Recruiting and hiring policies were as retarded and corrupt as management.
Hopefully, Trump’s order does allow the plants to close temporarily for deep cleaning in case of new outbreaks.