My rabbit/guinea pig has stones (uroliths) and/or sludge, how can I help them?

Dr. Sherwood recommends not feeding them greens and veggies including fresh grass.
They will eat more hay, drink a ton more water, and stop producing so much sludge and stop building the stone. Fresh grass from the lawn (and other greens) is super high in protein and minerals (including calcium) and will cause sludge and stones.

The reason why sludge and stones form in guinea pigs and rabbits is because of the Dietary Cation Anion Balance (DCAB)... or rather imbalance!

Cations are positively charged minerals like calcium, potassium, magnesium, sodium and more. Cations also include positively charged non-minerals. In the urinary tract the main one to be concerned about is ammonium (caused by excessive protein and an imbalanced dietary protein - this makes the urine stink like ammonia). Guinea pigs tend to have way too many cations (calcium is blamed because it is the only one that forms a stone but all cations influence whether or not that happens - explained below).

Anions are negatively charged minerals and there are very few options! Phosphate, sulfate, and chloride.

• The balance between cations and anions is very important.
• Too many cations → imbalance → kidneys don’t work properly.
• When that happens, the kidneys use a backup system that:
    - Makes sludge and stones (from calcium building up).
    - Makes the urine too alkaline (not healthy).
• Reducing calcium alone isn’t the answer—it causes other health issues.
  
• The real solution: balance the diet with fewer cations and more anions.
• Best approach: 
    - Feed 1st or 2nd cut dry grass hay (high fiber, low protein/minerals).
    - Pair with Sherwood’s pellets for the right nutrient balance.
• When you do this, you’ll notice:
    - Less urine smell.
    - Healthier urine pH (closer to normal, no sludge or stones).