Pigs were recorded in Domesday as having woodland to support them. Note that woodlands supporting pigs was primarily comprised of oak, since the pigs fed on the acorns they dropped.

Source 1: https://www.nationalarchives.gov.uk/domesday/discover-domesd...

In the modern world, you can manage about 5 pigs per acre. You should be able to do that many pigs or more per acre in the medieval world since the animals were physically smaller for the most part. So in an 80 acre pannage woodland, expect about 400 swine.

Some tree types are far more damaged by pig foraging than others since, if they don't get the yummy acorns, they tend to dig up roots, eat the saplings and do other damage. So the oak and the pig are good neighbors. The elder or the olive tree, or even the wild apple tree, all tend to suffer far more damage when used as pannage.

Source 2: https://acrcd.org/wp-content/uploads/2019/04/Pigs-and-Trees....