Red balls attract pigs in stables. Studies show that stable football drastically reduces the stress and violence of pigs (this effect is not seen in humans). Although animals spend a lot of energy in the game, pig players get fat faster than others.
Bernard Hoggarth, from the animal feed company called Cranswick Mill, says that when pigs get bored, instead of looking for their friends' tails or ears, they look for the ball.
Hoggarth imports plastic balls from Denmark. Attention to the animal ball is immediate and this ball is robust enough so that the animals are not damaged.