Hello! I'm sorry I did not see this sooner, I've been at work all afternoon.
How has your bun been doing now? If he's not eating and pooping, GI stasis like everythingducks said is likely the cause. A little odd he's hopping around acting normal, though. Normally they begin to act lethargic and lay around a lot.
I know epsom salts work with horses but I honestly have no clue if it works with rabbits. I'd look it up and do some research before I give any.
Stasis can be caused by a few things, the two main ones being one: a response to pain--if they're in pain, they can go into stasis because they stop eating. Or, it could be a gas or block in their stomach/intestines. It's very similar to colic in horses, especially since neither horses or rabbits can actually throw up. So if their stomach is not feeling well, they have to live with it, and blocks or gas can cause a build up which prevents them from pooping since their intestines are blocked. This essentially causes their whole system to shut down, and why it is so deadly to rabbits.
Maybe you knew that, sorry if you did! GI stasis is treatable at home, although just like the vet, there is not a 100% guaranteed outcome. There is a surefire method that can help, but sadly if the stasis is bad enough or if they take a turn for the worst nothing can be done. I've had one bad case of stasis treated with success with my method I'm about to tell you, and I also had one rabbit recently pass away despite my attempts; I think whatever she had was just too bad. I never took her to the vet but I firmly believe the vet may not have been able to do much more than I did.
You can treat your bun with baby's gas drops--I can't quite remember the dosage off the top of my head (I'm always forgetting...), but if you google it, it should come right up. If you need any help just ask me and I can look too.
You have to syringe-feed the gas drops into your rabbit; I also often use something called Critical Care by Oxbow to get nutrients and water into them. It's a powder you mix with water to form a paste that has a lot of good nutrients and is hay-based to get something in their stomach. However, I have no idea if stores near you sell it, so if you don't have it on hand it won't help you I know. But I thought I'd mention it anyways--I swear by this stuff--it is SUCH a life-saver and is helpful to get pills/medicine into your rabbits.
If you can't get critical care, and even if you can, you can also get baby's food pumpkin or sweet potato (with no extra sugar added) and syringe feed a little bit of this into them, too. It can help with stasis and is something easy to get into their stomach.
If the bun isn't drinking, I have also straight up syringed water into my rabbits before to keep them hydrated as well.
If you've never syringed a rabbit before, you have to do it very slowly and very carefully. Shove the syringe up into the corner of their mouth, and inject slooowly; if you go too fast you can asphyxiate them. I usually inject a little, make sure they swallow it (or if it's critical care / water / pumpkin, they might spit it out. That's okay--it's a messy process) before I syringe more.
Again, I'm sorry if you know any of this! I'm just giving a run down of everything. The last thing I'd suggest is gently feel your rabbit's stomach--if it is hard or bloated, it is definitely stasis. I'd also check nails, teeth, eyes, ears, and do a general check-over of the rabbit to see if anything is causing pain.
Once, my rabbit was not eating and acting out of sorts; I thought it was a mild case of stasis but was stumped, because my treatments weren't doing much. We ended up taking him to the vet, and it turned out it was a ripped nail. We got him pain meds and he was fine afterwards. That's just one example of, you never know. Rabbits hide pain well.
I wish you all the best and I hope your bun is still doing okay, and that I didn't come too late!
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