so here's what I know about poisonous plants...
in general, if an animal is raised around noxious plants, they tend to 1) not eat them and 2) not be as quick to become ill if they do. the local extension agent and my good vet in CA both said the same thing, they learn what not to eat, and they build a little tolerance to it.
that said, some things are poisonous only under certain conditions - for instance, johnsongrass is great forage unless it's been frosted, or it's under drought conditions, in which case it can be lethal. same for plants like maple which are dangerous only when starting do dry, wilt, frost-kill, or other environmental stress. the problem is some of these that are poisonous can become so overnight after a frost... so the animal grazes/browses them one day, no problem, there's a frost, and the next day the same plant can kill them if enough is consumed.
many things are sometimes poisonous... we've got poison hemlock... what the pros tell me is cattle, goats, sheep can graze it in small quantities, and around here often do, with no ill effects. but if forage is sparce, they may eat too much and die. it's not a 'first choice' plant for most animals if there's other things to eat. I think a lot of things that are considered poisonous may only be poisonous during certain times, or under certain conditions, but it's more prudent to just say Poisonous, rather than Poisonous If...
my horses eat milk weed, no problem. none of my animals will eat jimson weed... that one is something they're apparently wise to. all of them will eat the bark off of trees, including CA pepper which is said to cause stomach upset... except that my sheep and horses seem to have no problem and think it's very tasty. I've seen my sheep eat castor plants, another thing that is considered poisonous, when they escaped the fence, no harm done. my goats love the fallen maple leaves - doesn't bother them at all... but it's hard to know what quantity they actually eat. as with many things, a little may not do any real harm, but a large quantity might be fatal. other things are bad from the first bite.
so kill off or control what you can, fence off what you have to, provide enough other feed that they like that they don't need to eat the stuff they don't like, watch what they actually consume.
aaaaaand... this is part of why one would want to do a fecal first before treating, because as I mentioned somewhere earlier, worms are the likeliest cause of anemia, but not the only one... so you really need to know a bit more to be sure you're treating properly, not just "anemia".
another overlooked issue is copper... feeds/blocks/suplements/minerals for horses, cattle, goats shouldn't be used for sheep because the copper content can be too high and be fatal.
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for weight gain:
the T-A hay, as much as she'll eat, switching back to all grass once she's closer to normal weight.
small amount of oats (a cup or so) with molases if she likes that. we use oat/corn/barley mix with molasses, or dry.
some treats if she'll eat them (a carrot or apple) but not a lot of these.
probios.
you can add some dry powdered milk (a half cup to a cup) to her oats if she'll eat it... we use this for weight gain in horses too.
free access to sheep mineral / protien block like SweetLicks (make SURE you don't get the one for goats, but the one for goat/sheep)
free access to a white salt block
free access to grazing
expect her to gain a little slow at first - the worms will have done some damage to her gut and that needs to heal before she can really use everything she's taking in.
