For stones of any kind in cats, I think it is vitally important that you NOT feed a dry diet, so that's one strike against continuing to feed the dry diet. The most critical thing for stone formation is to increase water intake. The cat needs to be on a wet diet.
Diet isn't rocket science- we can read ingredient labels just as well as any vet.
Cats who form oxalate stones are supposed to eat a diet lower in oxalates and higher in calcium.
So the vet believes that Hills c/d is ok. If you look at the ingredients, it has 0.74% calcium (dry weight), and its primary ingredients are rice and corn gluten. Both rice and corn gluten are listed as "low" oxalate content.
Meats are usually completely devoid of oxalates.
So any food that has meat as the primary ingredient will be superior to Hills in oxalate content.
Calcium content Primal raw lists 0.53% calcium, and 95% EVO lists about the same, but I think these listings aren't dry weight. If you convert to dry weight, you get about 1.8% calcium, which is obviously higher than Hills c/d. Which, if you're trying to feed higher-calcium diet, means it's better than Hills c/d.
We need to find out the actual recommended amount of calcium for these cats to see if that amount is too high or too low.
I have heard that Primal's raw quail diet for cats is just fine for oxalate formers, so it might be.
I believe at this point the Hill's CD is supposed to take care of both struvite and calcium oxalate crystals. They used to have a different food for calcium oxalate crystals but I think they stopped that. I don't really understand how it works...
I don't see how it can work at all. Every bit of logic suggests not.
The few times I've deeply delved into the science behind Hills prescription diets I have always been left scratching my head in mystification. They often don't seem to be formulated to match the actual science, or at least the most current science, at all.
So I'll go poke around and see what the actual science suggests is a good calcium level for these cats and post. If anyone else knows, speak up.
But on the face of it, Hills c/d does not look like the ideal diet for these cats.
Last edited by wendy; Feb. 14, 2013 at 01:09 PM.
Reason: originally thought EVO calcium was dry weight, so had to correct it
Association between dietary factors and calcium oxalate and magnesium ammonium phosphate urolithiasis in cats.
Lekcharoensuk C, Osborne CA, Lulich JP, Pusoonthornthum R, Kirk CA, Ulrich LK, Koehler LA, Carpenter KA, Swanson LL.
Minnesota Urolith Center, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
To identify dietary factors associated with the increase in occurrence of calcium oxalate (CaOx) uroliths and the decrease in occurrence of magnesium ammonium phosphate (MAP) uroliths in cats.
173 cats with CaOx uroliths, 290 cats with MAP uroliths, and 827 cats without any urinary tract diseases.
Univariate and multivariate logistic regression were performed.
Cats fed diets low in sodium or potassium or formulated to maximize urine acidity had an increased risk of developing CaOx uroliths but a decreased risk of developing MAP uroliths. Additionally, compared with the lowest contents, diets with the highest moisture or protein contents and with moderate magnesium, phosphorus, or calcium contents were associated with decreased risk of CaOx urolith formation. In contrast, diets with moderate fat or carbohydrate contents were associated with increased risk of CaOx urolith formation. Diets with the highest magnesium, phosphorus, calcium, chloride, or fiber contents and moderate protein content were associated with increased risk of MAP urolith formation. On the other hand, diets with the highest fat content were associated with decreased risk of MAP urolith formation.
CONCLUSIONS AND CLINICAL RELEVANCE:
Results suggest that diets formulated to contain higher protein, sodium, potassium, moisture, calcium, phosphorus, and magnesium contents and with decreased urine acidifying potential may minimize formation of CaOx uroliths in cats. Diets formulated to contain higher fat content and lower protein and potassium contents and with increased urine acidifying potential may minimize formation of MAP uroliths.
PMID: 11697365 [PubMed - indexed for MEDLINE]
Ok, so compare 95% EVO to Hills c/d: EVO is much higher in protein, about the same sodium + potassium, much higher in moisture, higher calcium, higher phosphorus, about the same magnesium.
Since hills c/d is somehow mysteriously formulated to take care of both of these stone-forming conditions (impossible, but let's pretend), I assume it doesn't affect the pH of the urine? because oxalate you want higher pH, and struvite you want lower pH.
What effect EVO has on the pH of the urine is also a bit unclear. You might want to invest in some pH paper (check the fish section of your pet store), see what your cat's urine pH is now on c/d, switch to EVO, and check the pH again.
On the face of it, EVO looks to be the superior choice for managing this condition. Or, not to appear brand-biased, probably any of the mostly-meat canned foods or raw diets appear to be far superior to the prescription diet.
My cat had stones and was recommended to go on the vet diet. I just couldn't justify feeding my cat by-products and grains. It didn't make sense to me. She still got UTIs on high quality wet food, so I had to look for another option.
I put her and my other cat on a homemade raw diet and have never regretted it. No problems since and my cats have never looked better. I add lots of water to the food to ensure she is always well hydrated.
This information makes complete sense. I know my cat drinks very little water. He has one of those little cat water fountains which he likes better than a bowl but that alone was not enough to get more water in him. Now that he is on wet food exclusively there is a much higher daily urine output. I am thinking of switching to other brands of wet cat food with a high meat content that I can get readily at local stores.