Kale CAN cause gas (not as badly as things like broccoli, cauliflower and cabbage, but it can cause some), which is one of a few reasons that it should be somewhat limited (no more than around 1/3 of the total veggies given in a day and not fed more than 3-4 days a week). Pellets could potentially cause gas in some bunnies, I believe... however, if you haven't switched pellets recently, I don't see that being the culprit.
Lettuce is a great veggie as long as it's a dark green lettuce and not iceberg. Cilantro is another veggie that has no need to be limited.
This veggie list has pretty good information regarding oxalic acid content of veggies, but doesn't mention calcium:
http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
I used to link to 3bunnies.org for calcium info, but unfortunately that page seems to no longer exist *cry*
http://www.medirabbit.com/EN/Food/Food_main.htm is also good
With 3bunnies gone, I'll have to dig into my sugar glider links for calcium (which provide more in-depth info anyway). For what it's worth, I've actually heard from many vets that there is NO direct link or causation between calcium intake (from diet) and calcium-related problems like bladder sludge... however, some vets and owners will say otherwise. I've got no conclusive proof to offer either way, so I recommend that rabbit owners decide for themselves how cautious they feel they should be regarding calcium in the diet.
As a note, the glider pages also contain phosphorus information - this is because phosphorus interferes with calcium absorption. A 1.5-2:1 ratio is recommended for them...
http://www.therabbithouse.com/diet/rabbit-food-comparison.asp also cites 1.5-2:1 as the ideal ratio for rabbit pellets, though it doesn't mention if that applies to the overall diet as well. If that goes over your head a bit, feel free to disregard it, lol - Ca
stuff gets awfully complicated and "mathy". In the glider world, people tend to get way too hung up on it instead of simply feeding a very wide variety of fruits and veggies - I don't want to send rabbit owners down the same path!
I recommend that you avoid feeding large amounts of things that have a very high ratio of calcium to phosphorus and leave it at that:
http://www.gliderkids.com/FruitVegLIST2011.pdf
http://www.sweet-sugar-gliders.com/calcium_phosphorous_ratios.pdf
(Please remember, these are resources for sugar glider owners - I don't remember everything on those pages... there's no guarantee that all fruits and vegetables listed are safe and/or recommended for rabbits. For rabbit-safe fruits and veggies, you can check
this page.)
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Back to the gas issue... rabbits typically have a very hard time getting rid of gas. If he's passing some of the gas, that's always good; however, it doesn't mean there isn't more gas still trapped in his digestive system.
I suggest giving simethicone (any brand of OTC baby gas drops) - simethicone is VERY safe for rabbits. Recommended dosing is 1-2 cc every hour for 3h, then 1 cc every 3-8h as needed if it seems to be helping.
While you're most likely in the clear if you treat with simethicone and ease up on the gas-causing veggies, it IS possible for a gassy bunny to develop GI stasis as a result. You need to keep a close eye on your bunny for the next couple days to make sure that he doesn't display any decrease in appetite, that there's not a noticeable decrease in fecal poop output and that you don't see him sitting hunched up (similar to how a person might if they had a tummy-ache). Another sign to look for is if he's frequently laying down only to get right back up - this can indicate that laying down puts pressure on the trapped gas and makes him uncomfortable. If you see any of these signs and simethicone is not helping, it's time for a vet visit.
Please keep in mind that if a bunny goes 8-12 hours without eating and/or pooping, it's considered a medical EMERGENCY! Rabbits have a digestive tract that needs to constantly be moving - GI stasis can easily be fatal for a bunny if left untreated.
