At one time, the lucky pigs were much smaller. Five months later, they are a lot bigger.
Traditionally, pigs have played an important role as the utilizers of food waste. As Harris explains in his wonderful book "Harris on the Pig":
Pigs will eat food which, but for them, would be wasted.Cows, chickens, goats, ducks and geese don't gorge themselves like pigs - which is unfortunate.
As diet (after genetics) is the second most important factor determining fat and meat quality, one must optimize the diet to control quality and cost. Feeding pigs free fishmeal and potato chips shortly before slaughter produces awful fat. But feeding pigs that stuff when they are young might be optimal, because if one can finish the pigs properly, they'll produce excellent fat and meat at an affordable price.
Hence, although old bread is not proper finishing feed, these Mangalitsas are at least a year away from slaughter, so they get to eat it. They really have a lot of fun playing with their food.