I've had goats for several years, and am a budding pig farmer. Our terrain here is very steep high elevation; dense conifers, woody brush, lots of gravel where there needs to be soil, lots of ground
water. We're thinning out the trees so they can be healthier and so that something other than maple, dogwood, huckleberry, and alder can grow amongst them. Like... grass. And pasture. Running the animals on this ground will also help to build soil.
So our first 'pasture' was an experiment with the goats. We electrified several acres around a draw with a creek. At the very least they would reduce fire hazard. They're good about pruning the trees (needles, smaller limbs, and lichen) up to 5-6' high and cleared out most of the brush and undergrowth. 2 large goats (around 200lbs) ate everything there was to eat in a season in that area.
So now we're moving them into another draw to do the same. In their wake, in the previous 'pasture', we're putting the pigs. We want to see what they make of it. We have full size pigs and miniature pigs. The full size pigs are tilling machines, and are especially fond of consuming stumps and
roots, which we appreciate. We also want to see what the pigs do to the creek bed. Right now it's spread out in many areas, forming little bogs before narrowing down int o a creek again to the next boggy area. We're going to see if we can encourage them to wallow in specific areas and what they can do as far as "making ponds" in the draw. Anyway. The goats stripped out most of the brush and small trees, now the pigs can go in and
root up the remains, leaving the way much clearer for thinning trees and for seeding new growth.
Obviously we have different terrain. But I hoped to maybe illustrate how these animals are functioning for us on the land. Goat are difficult to contain, yes. So are pigs. A large pig can easily pick up several hundred pounds of weight and go underneath it (we tried strapping logs onto the bottom of our fencing to keep them from going under...). So far electric fencing has been the absolute best. It is THE CHEAPEST factory-made fencing you can get, per foot, and it works to keep animals in and predators out. A high-joule charger will resist a lot of grounding. We're running a 6 joule charger that uses less than .5 amps from the battery/solar setup its on, cranking out 10,000 volts. It makes animals not want to touch it twice, which is very nice. Makes me not want to touch it twice, too xD I always bust up laughing at the blood-curdling involuntary scream that rips out of my throat when I get zapped. It doesn't even "hurt", really, it's just startling to the senses.
Anyway.
Goats will strip out the BEST of the best and move on if they can. Don't expect a herd to focus one blackberry patch down to stubble before moving on. To get them to destroy a patch of something you need to pen them in with it. Although, as mentioned before me, the one exception may be fruit trees. They will spend every waking moment of their day focused on a fruit tree;
wood, bark, leaves, stems, you name it, they want to eat it. They will ring an
apple tree in a heartbeat. However, as others on this site have learned; macerating meat in
hot water (making a rotten meat slurry) and painting that onto the trees will definitely keep a goat from eating the tree, without harming the tree. Plants love that slurry!
How well a pig tills your earth depends on the breed, probably. We got Mangalitsas for their cold hardiness. You could easily run pigs to tackle brush and brambles, especially if they're good foragers. They can reproduce and give you an organic, pastured meat product too. Our pigs are dog-like and love attention and interacting with us; but that's also characteristic of their breed. I fully expect a pig to strip bark of a fruit tree just as a goat would, but they are perhaps easier to deter int the sense that they're not going to CLIMB the tree. Ringing your trees with sturdy wire skirts up to 3' high would be
enough to protect them from the pigs.
And we are able to run our goats and pigs together. Granted we've only got a couple of each and have made certain they interact peacefully. They make a nice combo team for stripping land.
One suggestion/partial solution would be to create a central feeding station for your animals. If they have ample forage plus get tasty treats, they're less likely to get bored and test the fences. It could be handy to have your browsers come running to you when you call or whistlem telling them you've brought grain or whatever.
BTW - goats are grain addicts. Like... it's like cocaine for goats. At least my goats. They get one taste of it and they turn into grain-obsessed screaming fools. They can think of nothing else, and no punishment is severe enough to deter them from trying to get more grain. I have to ween them down off grain every time they get into it. I don't normally grain them. But this is VERY handy, because any respectable goat will readily take a bribe. And being able to shake a grain jar and have your goats do ANYTHING you want them to is so unbelievably handy ;)