It's not about saving the animals, fools. The ALF isn't trying to "liberate" the minks, thinking that they'll somehow be able to survive in the environment. If the ALF had their way, they would choose to euthanize the minks. These acts are about putting it to the farms.
For one, it screws up their breeding programs. The minks are typically put into cages, and the cages are labelled. When the mink are released then recaptured, the farmers don't know which is which. And now, when they get thrown back into the cages, this cannibalism is occuring, further fucking the farmers.