Re: Guinea pig with bladder stone, Which veggies should I feed him?
Sorry, but bladder stones are serious ALL the time, especially in males. Their urethras are usually too narrow and too long to pass even a small stone, and if the stone falls into the urethra and blocks the flow of urine, the pig can die a very painful death. Occasionally the stone can be flushed back up into the bladder where it is surgically removed, but even that fails a lot of the time because the stone is too sharp and spiky to be flushed backwards.
Stones should be removed when they're found. If it were my pig, I'd be scheduling him for the first available surgical appointment with a good exotic vet surgeon.
As far as diet goes, you want to aim for .4% calcium or less. The only pellets in the US that come close to that are those from KMS Hayloft, available only online. They have the added advantage of also being the only ones that don't use limestone as the calcium source, and limestore is definitely implicated in urinary stone formation. So I'd either switch him to KMS pellets, or take him off pellets altogether.
Romaine and coriander, although no higher in calcium than other lettuces, can cause excess urinary calcium in some pigs. I'd avoid those altogether -- red and green leaf lettuces are much better choices. No parsley or most other herbs, either -- they're usually high in calcium.
I have a stone pig, and this is what my two get (for the both of them):
No pellets, unlimited timothy hay. For breakfast, a chunk of carrot and some red or green leaf lettuce. For midday, 1/8 head radicchio, 1/2 head of belgian endive, 4-5 young green beans, 2-3 wheels of zucchini or other summer squash. At bedtime, 1/3 tomato, 1/4-1/3 bell pepper, and more lettuce, unless I can get fresh corn. If I can, they get the inner husks and silks of the corn instead of the lettuce.
Here's a chart on what you can feed them, and how often. It's a little out of date, but still usable:
https://www.guineapigcages.com/foru...vy-Nutrition-Charts-amp-Poisonous-Plants-List