Is a Jewish farmer allowed to raise animals for non-kosher slaughter? Does it make a difference whether it is a non-kosher animal (e.g. pig), vs. a kosher animal? Does it make a difference whether the farmer expects to sell most animals for kosher slaughter, but sells a few for non-kosher slaughter, vs. when the farmer expects that most or all of the animals will be sold for non-kosher slaughter? Is the situation different for a farmhand than for the one who owns the farm?
One may not do business with food objects as food if they are biblically forbidden to eat, except Chelev (certain forbidden fats) which are specially excluded (Leviticus 7:24) from this prohibition. If one happened to acquire such foods he may sell them, but should do so immediately. (my summary of Shulchan Aruch YD 117)
Accordingly, one should not raise non-kosher animals to sell as food. One could raise kosher animals for non-kosher slaughter provided they are sold before slaughter.