Foxes do indeed eat rats anagallis_arvensis. Which makes them the only natural predators which will kill rats in towns. However feeding rats is of course quite unnecessary, as humans through their unhygienic habits and life styles will always ensure that there is a plentiful supply of food for them. Let’s just hope we always have a good supply of foxes to deal with them.
They dont need feeding with anything, leave them be.
The RSPCA release urban foxes from their animal hospitals back into the countryside(illegal I think)and the bloody things either try to take Lambs or starve to death as they dont know how to do anything other than tip bins over or eat dog food left out for them!