Bladder stones are a common condition in guinea pigs and are found to be quite painful in most cases. Bladder stones are small masses of minerals that the body wasn’t unable to absorb which led them to crystallising in the urinary tract. They can be found in any part of the urinary tract, starting at the kidneys and all the way down to the urethra. 

For a guinea pig that needs to gain weight, it may be best to temporarily change their hay type. Grass hays are recommended due to their low calcium, low fibre and low protein contents. However, switching to a hay that's higher in these nutrients, like alfalfa or oat hay, may provide immediate results.

Guinea pigs will produce 100 poops a day on average, with the number reducing gradually as they age. However, it’s hard to count exactly how much poop guinea pigs will eat in a day since they only eat a certain type of poop.

The type of poop your guinea pig will eat is called caecotrophs. This type of poop is the first poop they take after a meal and they will eat it almost immediately before our eyes.