If you google/search-engine-of-your-choice for the key words "livestock, plants toxic", you should get several lists. If you narrow it down further for PNW or for Oregon or Central Oregon, you should be able to eliminate East Coast only plants. There are some plants that are only in the West, as well. I would look at several of the lists and make your own composite, as some lists are more complete than others. I think UCDavis puts one out, and probably the Ag./Animal Husbandry Dep't at the state University in Oregon does too. If all else fails, see if your county's extension agent's office has a list.

I forgot to add that for the ones I know of, there are: red maple, and any cultivars thereof, as well as possibly silver maple; wild cherry; many of the oaks, especially acorns; any of the Rhododendron/azalea family, including Kalmia/mountain laurel; yews; (not that they are hardy for you probably, but...) oleanders; any of the solanum family - the plants and leaves, some of the fruits are OK if not green, such as potatoes; and the perennials and ornamentals such as aconite; amaryllis; anemone; caladium; clematis; larkspur; lily of the valley; foxglove; Datura; delphinium; hydrangeas; iris; lantanas; sweet peas; lobelia; lupine; ranunculus; and tansy.

There are any number of others, some local to your area, so I would do a search to see what you should cut down or not plant. Some, such as nightshade or jimson weed/datura, may well be growing as weeds for you (as if you WANTED them!), and may well reseed for a number of years, so you will have to be vigilant if they are already there or are growing in the vicinity of the pasture.

Not all of these are equally bad for all livestock, and not many are necessarily attractive to livestock, but why take the chance, especially if you plan to pasture goats, sheep or horses together or in rotation.

Talk to your extension agent and conservation district as they can help you.

You can probably plant trees/bushes such as chinese elms, russian olives (now listed as noxious in some areas but still a great drouth tolerant windbreak), junipers, pines, etc. Don't plant chokecherries as they cause cyanide poisoning when the leaves are green in spring and summer and the animals eat them--plant them where the livestock can't get to them. Hopefully you have irrigation or you will be limited to the most drouth tolerant species, which means to look at the native trees and bushes in your area, and you will probably have to keep the livestock out of them.

I would be a little leery of both the Chinese elms and the Russian olives, since both of them are listed as invasive under conditions similar to yours. Even if they aren't a problem in your pastures, they may become one in the remaining wild areas. One of the reasons they are so invasive is that they are really GOOD at making do with your conditions, dry, wide temperature differentials and windy (which would disperse seeds far and wide!).

See if there are any natives that will grow in your area, as well as any introduced species that aren't so prone to taking over. Natives would also give protection and food to the wildlife around, which it sounds like they might need, what with development clearing land.

Try your County extension agent for suggestions, since he/she should have several lists that should help, both with suggested plants and with poisonous plants. I would double check all suggestions, however, as sometimes the listngs are neither accurate nor up-to-date.

Why has no one thought of using windbreak plants as livestock feed?

Thankfully, although God did invent multi-tasking, he didn't require it. A shade tree can be a fine screen, as can an evergreen, and both produce a seed of some type, which can be used as feed, just not all trees can feed all animals.

Did you know horses like to nibble bark? Yet another reason horses deserve a fine home...just not one near me.

Robinia has been researched as a forage, with promising results in the trials I have run across, although it has to be harvested and processed much like alfalfa (haylage), something which I don't think you are looking forward to doing.

Gleditsia has extraordinary nutrient content in its seeds, with reports of nearly sixty percent sugar and protein, depending on variety, and a storage period of a couple of years. What I am not clear on is the protocol for feeding...are the seeds to be removed from the pods or not; ground into a meal or not. Not at all sure about removal from pods; I suspect meal processing is part of it.

Your most sensitive animal is going to be the horse; basically, avoid red maple and black cherry to keep your pets from getting a tummy ache. That being said, if red maple and black cherry were toxic in all parts at all times of the year, there'd be very few horses in this country, as these trees are practically everywhere.

There is an archaic term called mast that has nothing to do with sailing. It refers to the number of head of livestock of whatever kind that can be shaded by a tree, as well as to the feed that tree produces. Historically, a property owner could be recompensed for the mast value of a tree should the actions of another damage it.

If development is encroaching, you will also need to keep an eye open for traveling plants. Neighbors may plant something toxic in their yard as a specimen plant, and the birds/wind will spread it to your acreage. If you can give your neighbors a list of invasive, non-desirable plants and explain about your livestock, they may cooperate.