Hi here is an idea for you to try a feeder only wild boar can opperate.
Parts needed: 45lt steel clamp lid drum, I large steel swivel, some steel bar 10" long, a length of wire rope, a front wheel tractor tyre or similar, bag of cement and gravel.
Drill 4 or 5 holes through the tyre wall and corisponding holes in the base of the steel drum and bolt the 2 together using large washers to stop the bolts pulling out of the tyre.
Now stand the drum upright with the tyre upper most, fill the tyre with a good strong concrete mix, now push the iron bar through one eye of the swivel and sink this into the centre of the concrete filled tyre, so that it cannot be pulled out once set.
Drill holes in the drum, evenly spaced in 3 places around the drum and also top middle and bottom of same.
Fasten the wire rope to the swivel one end and a steel hoop arround an imovable object in your chosen place, 2 metres of rope will do.
Fill the drum with feed and clamp the lid on.
The only animal cappable of pushing these around are pigs and as the feed comes out they eat it, when they stop, the feed stops and nothing else [except mice] gets to it.
You might find an eye welded to the top side of the drum and a handy pulley fastened to a local tree will help stand the drum upright for easy filling.
These feeders are used in europe and they work well.