Rabbit forage - what time of year to stop harvesting as you go?

Question about foraging for rabbits. I fed my colony and tractored rabbits all spring and summer on a small amount of pellets, all the hay they wanted, and once a day I'd bring them an armful of forage. Fat happy fast growing rabbits. In previous years, I did pellets and hay alone, got happy rabbits but this year they seemed happier. Towards the end of summer I had trouble with some of the younger ones dying, both tractor and colony, at the same time, but not the caged rabbits, who I don't bring forage to. I thought I must have fed them something they shouldn't have done, but i hadn't changed anything, the same handful of species I'd been feeding all summer (goldenrod, ragweed, knapweed, thistle, nettle, dandelion, aster, bishopsweed). The only thing that had changed was the weather - also a new bag of food but same food, same supplier, no funny smells or difference in colour or consistency from the old.

It's the first year I've fed primarily forage and the first year I had a tractor. Wondering if the change in season meant a change in the plants I was feeding - I read somewhere that some of them can have more oxylates as fall comes on, maybe the balance got thrown off. So I've got two questions:

1.) Does anyone have a great site for this, i.e. don't feed X plant at Y time because of Z reason?

2.) I had left a meadow with some of the plants I'd been feeding wth the intention of pulling them in Oct / Nov / Dec before snow gets too deep. Considering the potential change in content, should I have harvested them in July or August and dried them, rather than leave them standing to harvest as needed?

I don't have any answers for you, but want to watch this thread -- I'll probably be getting some rabbits again next year, and want to feed as much forage as possible.

It's always wise to positively identify what's growing(and look up whether it's safe for them), before feeding it to rabbits. They will eat most of what you put in front of them, if it's tasty - even if it will kill them. Domesticated rabbits don't survive, released into the wild, partly because they're not so well practiced in exercising their instincts, partly because they're not as physically fit as their wild cousins, and partly because they don't know what's safe to eat, when their primary diet, over the course of their lives has been pellets and hay - they just don't know what it looks like, or what to avoid. That's not on you - it's on their long-term breeding. But, it does dump a whole lot of added responsibility on their owners' shoulders, as far as learning what's safe, what's not, and pulling out what's not.

Yep - hence the post. The plants I feed are positively identified. Like most patrons of this website I nerd out on that sort of thing.

I wonder if there could be something fungal on the fodder plants, something that only grew due to the change in the weather.

Could the young ones have parasites because their immune systems were not strong enough yet?  I’m in southwestern N.C., Appalachian mountains and liver fluke is a problem here, as snails are the hosts.  Have to worm the goats for that, and sometimes I see small snails on the forage I gather for the rabbits, which I immediately remove and throw away that part.  However, it might be left in the slime they leave behind on forage and what if I miss one here and there.  I always make sure forage I gather is dry with no dew or rainwater on it.  That helps somewhat.  Foods high in tannins occasionally, like small amounts of oak leaves or lespedeza, can help rid parasites.   You can use ivermectin, oregano, basil, green pine needles.  Not much.  Too much can be bad for them.  I hope someone with more experience will chime in here.  Things like liver fluke are harder to get rid of.  For goats I use raisins covered with copper sulfate, 1/4 tsp. Per adult goat for two or more days in a row, but don’t know if rabbits could tolerate that at all.  

Are you feeding a wide variety of forages so they don’t get a lot of any one thing on a given day?  

Also, some plants become toxic when hit by frost.  Things like kudzu, stone fruit leaves, sorghums.  
It is very hard to get hay here isn’t moldy.  You can’t always see it, so I smell of any hay I buy for the goats.  Still haven’t been able to find any they will eat, so gave up and make tree hay for them.   The rabbits prefer the same so they get it too.  Goats eat the grass in the pasture, when it is young and vital, but people in this area who make hay generally let it go to seed when the nutrition is poor, and then it rains on it a couple of times so quality really is bad.  

Rabbits are very sensitive to molds and fungus, and their food needs to be as clean and wholesome as possible.   I’ve planted oats and wheat, and winter peas for them so I can cut and harvest over winter.  Oats will winter kill, wheat is more hardy.  We’ve had a light frost already so not much available that would be safe for them now.  

I was thinking along the same lines as Faye, did you necropsy the dead rabbits? i'd be concerned about some sort of ground-based parasite first, frankly.

Fungal might very well be it, I live in SW Ontario on top of a cold spring fed swamp / pond / meadows and some hilly glacial till, frogs abound. We have a spring wet season (aside from the snowmelt) and a fall wet season - though it was , as everywhere, a weird year and we had the super long spring, then weeks of dry (very unusual here) and then a week of hard rain, repeat.

Miiiight be the hay, couldn't say. It smells dry, looks dry, orchard hay, but no pesticides / fungicides were used. I only buy a few bales at a time and it sits in a neighbour's barn all winter. Could be something on that that didn't take until later on.

Yes to necropsy - some liver damage but not much, about what I expect for ground dwelling rabbits, I muck out their colony regularly and they have a big old run but there's only so much you can do - life is trade-offs. Some of it was bloat which I hadn't had before really since my first days years ago, and this is why I thought it was something I fed them.

Thanks for the tips on worming. I haven't been worming them but some of what you mentioned is already growing here and I can see if ivermectin is available anywhere.

If it's fungal.. I could harvest during the dry season in July / early August and put it up to hang in the garage, feed that during the fall wet season rather than pulling from the ground as I go. Too late for that this year but certainly next. Some of it I don't positively know what it is until it flowers in September, like the asters, but might be they just don't get asters even if they *do* love them. Unless it's a dry fall.

Sidenote: phragmites australis, that invasive reed along the roadsides. A patch has popped up next to the pond, though it doesn't seem to want to take it over (I think the water is too cold, there's no swimming in it any time of year). I saw a study of people feeding that on the other side of the planet, and I think I saw one mention of it somewhere on this site - want to bring that option up again and see if anyone's been doing it? I'd be happy to donate some sweat to a conservation authority in exchange for taking it all home (sans seed heads) and drying it for winter forage.

oh and yeah they do get at least four or five varieties of forage every time so they can choose what they're craving, and they don't get it until midday or so so they've eaten their pellets and hay first and aren't starving, and also so the dew's dried. But the snail stuff would have dried too, won't have seen it.