Well, I don't know about horses, but I have been having a deer problem for the first time and I googled "deer resistant plants." Maybe you could do the same for horses and goats.

Horses and goats shouldn't knowingly eat anything that is poisonous to them. The only time toxic plants are really a problem is when they are cut and mixed into hay or feed so the animal is unaware and unable to sort it out.
Additionally, the plants that are on the "very toxic" list are not vining plants. So, I wouldn't lose too much sleep over it.

Take into consideration that the horse owner will possibly be going along the fence line with a weed whacker in order to keep the fence free from all things green. A fence free of greenery is much easier to check on for gaps etc ..

No, the horse owner won't be going along the fence line with a weed wacker. She's 80. Her son, in his 50s rototills as close to the fence as he can with his lawn tracktor tiller.
They finally put up a proper fence after 2 that their horses destroyed! They put the fence holders on backwards so when the horses hung their necks over the fence it would just slide down!
After the first time telling them about their mistake, I didn't offer to pay for 1/2 the fence when they did it again!
Thank goodness they did it right this time!
Now I just have to plant something to block out the horse dust! NT

Well if their horses can't respect a fence and are hanging over it all the time, I'd suggest something very prickly! My mother's pasture horses (despite being well fed) are always reaching through and eating as far into her border garden as possible. Even Cleome doesn't have a chance to mature enough to develop it's prickers. Vegetables are completely out of the question as they will not survive long enough. I'd say climbing roses are probably your best hope. Bamboo sounds too edible to me.

The climbing roses were in my thoughts also!
They might get a few leaves to munch, but not much more.
I'll run that past the neighbor. Thanks
Nancy

Hi Nancy! I love my plants AND my horses, so I can see both sides of this issue. :-)

I just wanted to say that although the previous poster is MOSTLY correct, some horses will eat a poisonous plant, especially if they don't have anything else to munch on all day. As grazing animals, horses are designed to nibble nearly all day. If this need isn't met with a constant supply of grass or hay, many of them will chew on whatever is handy -- poisonous or not. Incidentally, this may include "pricklies" like roses.

I'd never try to grow anything on my horse fences because even if they don't actually eat the plant, they'll play with it until it dies. Blocking dust with some nice, thick foliage planted a few feet on your side of the fence is a good idea, though. You can always call your local equine vet to ask whether a paticular plant will hurt the animals should they reach across and steal a leaf.

Good luck -- that's frustrating! (I know. My neighbor's horses got loose into my garden several times last year. Grrr.)

Yes horses are designed to nibble all day. If you are worried about horse dust I am betting they are not on grass but have eaten it all down or are on a sand lot. My horses are stabled indoors with only supervised turnout and I can vouch for the fact that they will nibble. Anything. Even to the point of starting in the middle of a plank wall. I still think they wouldn't eat enough to hurt themselves unless they were at risk of starvation. Here are two good links
http://www.ansci.cornell.edu/plants/horselist.html
http://ohioline.osu.edu/b762/b762_24.html
http://www.ansci.cornell.edu/plants/horselist.html

I live in horse country, and virtually all of my neighbors use a wild rose of some sort along their fences. I should know what it's called but I'm a novice, so I don't know! Then there are the briars - some sort of Himalayan blackberry. Those are really nasty!

As for the deer mentioned, I've found a few tricks. I'm west, not east, so our deer don't have the same taste as yours do. But I've had great luck with putting Snow Crystal Allysum (annual) absolutely everywhere that I don't want the horses to nibble. The strong smell seems to be quite a deterrent. It's not foolproof, but it seems to be effective for the most part. Also, of course, I don't plant any deer candy!

Farmer, thanks for the links! I really don't want to poison my neighbor's animals!
Nancy

I put allysum where the deers were feeding and they seem to be doing the trick.