I know goats will eat buckthorn but in my limited experience they will eat everything else first. Does anyone know if they will focus more on buckthorn either in the early spring when it's the first to leaf out or late fall when it's the last thing hanging onto it's leaves?

We have around 100 acres to clear of it and it seems impossible. The neighbors also won't do anything about it on their land so it will need to be continously managed

Grazing is considered somewhat effective in knocking honey suckle back but is not really good at eliminating it. Also with 100 acres that is a lot of area to cover and it will take a lot of time or you need a ton of goats and that means a lot of fencing unless you don't care if they our out a lot.
There are types of Round Up (glysophate) where you can spray and kill the growing vegetation and graze or cut 3-4 days later which may work in keeping ahead of the emerging plants. Downside is you will have killed all the other vegetation as well.
Bryce

If goats work I may get 1 or 2.

I had the Forester at my property this week & he said buckthorn can be treated in the winter. Maybe he was talking about using Tordon because I didn't think the Garlon I use via cut stump treatment would be effective in winter. Intriguing though.

personally I would never use goats on any property that wasn't in really sad shape to begin with. Even then what the goats do will not guarantee elimination, just knocks them back for a year.

I killed most of my Buckthorn using the basal bark method using Garlon 4 for the herbicide mixed with diesel.
Gotta be careful with it tho and avoid over application.
My place (approx 20 acre of woods) that had Buckthorn did not have it very bad. Scattered in 3-4 areas and none of the areas it was dominate.

Goats will never clear 100 acres unless you Fence them in small lots, and then everything gets eaten before moving them to the next lot....more goats work faster but it will take some time.

I'm planning on going to a goat demo at the state cranberry research station in August if anyone is interested

Currently I'm skeptical of goats, although one of my three properties has such a massive Buckthorn problem that it probably can't hurt to try goats, and since the worst problem is at my home property it would be a little easier to own a goat. The problem I see is that my guess is goats would eat anything they can get their mouth on. If they eat grass that would be a plus, b/c I don't like to mow.

My uncle has goats for pets, but he hasn't used them for eating invasives. I'm not sure if all goats are good for brush removal

I’d control burn the whole thing if possible

As a goat owner I will tell you that you are wasting your time.

We had 40 something at one time. They eat what you most want them too last 99% of the time. The cost to fence 100ac to reliably keep a goat in will be significant

On top of that if you do not have rocky soil you will be trimming hooves regularly AND they are the most parasite prone critter I have ever owned.

If I had 100 ac of "brush" I would hire someone with equipment to get it cleaned up. Think heavy equipment, push up and burn.
Then get a sprayer, educate yourself on the best herbicide for basal spraying the targeted species and get to spraying any new growth.

100 ac is nothing to attack on foot unless the undesired stuff makes up a small percentage of what is there

There's a business called brush busters that rents goats out to people with overgrown land in the Charlottesville ,VA area. I have seen the goats @ work. I don't know exactly how it compares to using herbicide. But roundup is slowly being phased out by local laws. I do have a landscaper that uses Roundup on the sly. Whenever a car drives by they stop spraying. They have a lookout dude who yells "car". At least one other state has phased out roundup for non row crop usage.

I have 20 acres of woods too. I thought about the goat idea. After a little research, it is as you say. It knocks the buckthorn back for a year, but comes back the next year.

I cut the larger plants down and paint the stumps with undiluted Crossbow. That kills the tree. New emergent plants can be killed with a diluted Crossbow spray.
I also have an abundance of prickly ash that I treat the same way as the buckthorn. The prickly ash is much easier to kill than buckthorn.

He does not need to fence the entire property. He only needs a 3 to 5 sections of premier 1 electro net fence a battery, solar panel and energizer. Then just move the fence when they have eaten it down.. hoof trimming I'd once every 3 months and simple. Parasites are much lead of an issue tlwhen you are moving the goats around vs leaving them in the same area. Mowing my path, Moving my fence pulling and driving the ground rod only takes an hour and half maybe 2.

Instead of fencing, could a person put the goat on some sort of leash/anchor with swivels?

Yes, but I did have one get into yellow jackets and couldn't get away from them like that . I won't do it again and do not recommend.

When you use a rope you have to be careful that the goat doesn't strangle itself. Yes, it has happened unfortunately.

Use chemicals and mechanical means of pulling. I've waged war on buck thorn. It is the Devil of the Woods.

I wanted to use electronic dog collars. I've heard goats can be trained to it and they're cheap compared to goat fence

This sums up exactly what I do and have experienced.
I'm not sure how forests in Wisconsin are going to have a future because most people are doing nothing about buckthorn.
I would imagine there's a risk coyotes and bobcat could harass a goat
On an infested property it'd be easy to keep a goat busy all summer probably, but during the off season I'm not sure what the best thing to do with the goat would be-- perhaps find a farmer willing to hold it

AJE, in the off season - butcher and eat the goat. Problem solved!

Well if he can mow paths through it, I would mow what I could and basal spray the buckthorn. Goats are not going to kill brush too big to mow anyway, they will only clear the vegetation they can eat. Ground to 4' or so.

Bottom line is you have your opinion of goats and as a FORMER owner of goats I have mine. OP needs pros and cons to make a decision and I am just providing some cons