Hi there, welcome
There are some buns that just can’t handle veggies, or can’t handle much variety. It is a good sign that she has normal poops mixed in the with the weird ones.
Oval poops can sometimes be from molting if there is too much fur being ingested, do you notice any connection with her molt cycle?
I had experience with a foster that had weird poops (large oval ones, soft misshapen, large piles of unformed due to cecal dysbiosis), and we suspect he was a megacolon bun, or some version of cow pile syndrome. But, his poops were NEVER normal, and he alternated between gross weird poops, and gas and stasis.
In caring for him, I did a lot of research on the topic. How old is your bun? And what do her markings look like? Since your bun has normal poops mixed in, I don’t think she would have megacolon or anything like that… unless she is very young and it is just starting to onset. One last thing about megacolon/cow pile buns, is that they tend to start loosing muscle mass because they don’t correctly absorb nutrients in their cecum. So, if you are concerned you should start tracking her weight. If she starts losing weight with no other explanation then you should consult with your vet.
It’s wonderful she is a good hay eater, as hay is 100% the most important part of the diet. You can offer a larger variety of grass hays (oat is usually a popular one) to help give some variety if she’s not getting veggies.
Many sensitive tummy buns also benefit from a switch to more “natural” forage, vs. veggies grown for humans. Dandelion, sow thistles, narrow and broad leaf plantain, fennel, and mint are all good ones. Carrot tops are also a good one. Plantain (which is a weed that grows all over the world) can be very good for sensitive bunny tummies, and is easy to collect and grow yourself (just be sure to collect from an area that isn’t near a road or sprayed with chemicals, and wash well). Dried veggies are also sometimes easier on bunny tummies than fresh ones.
With any new food, start with just a small amount and see how they do with that for a couple days.
You might also try a pro-biotic, Bene-bac is a good one that most bunnies like.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.