Blood in Stool x 7 Cats

Question
I run a private, non-funded animal rescue in my home. People e-mail/call me with cats that are abandoned or in need of homes, and I take them in. They are provided with a warm, loving home until I can find them a loving permanent home. I've found homes for about 18 cats so far! The problem is, 7 of the 12 cats here have blood in their stools. The stools are also lightish yellow in color sometimes, the blood is bright red and there is only tiny amounts of it. It can't be worms, because every new cat is quarantined and de-wormed before being introduced to the rest of the house, and I took some stool samples in to be checked for eggs last week. Negative. My only other though is that it might be their food? Because I do this out of my own pocket they are kept on a relatively cheap brand, while still trying to satisfy their nutritional needs. They currently eat "Special Kitty", a Wal-Mart brand. It's dry food, which they have free access to. We use it because they don't use corn in as high amounts as other brands, and they don't use preservatives like BHA/BTA. Ideally I'd feed them raw meat, but it's too expensive right now. Anyway, that's the only food they get, although I give them wet food when I can(it's random), because I know the moisture content in dry food is not acceptable, especially for male cats. So when boiled down, my question is, since it's not worms, could the food be causing the blood? If not, what could it be? They display no other symptoms than this, they seem happy and healthy, playful, no lethargy, good appetites,etc. Do I really need to be concerned? Thanks in advance!

Answer
Well you won't like my answer but yes, it is the cheap Wal- mart food that you are feeding that is causing this. Corn is not a problem in cats or dogs either, being one of the best bio-available foods and having an extremely low allergen rating.
Having said that, buying cheap food costs you a lot more in the long run because you are not meeting the energy needs of these cats with it and you are most likely buying a lot more than you realize.
When animals eat cheaply made food it can be very irritating to the colon and when the stool is hard with this less-than-ideal food it can cause the vessels surrounding the rectum to rupture and bleed when they have a bowel movement.

I know that more expensive foods seem cost prohibitive considering what you are doing for these cats but raw meat is not only expensive it is completely unbalanced and a good way to push a cat toward early kidney disease by ingesting too much protein and an imbalance of minerals and nutrients such as calcium and phosphorus.

I had 9 cats at one time and when I started them on Science Diet instead of the cheap Farmer's Market brand I had been feeding my cats not only got much more healthy but their food intake went way, way down! After selling this food for over 27 years and becoming a Small Animal Nutritional consultant with Hills and CNM by Purina, I can tell you that the fact that Wal-mart and almost every other food out there does not use what we call 'fixed formulation' in their processing of their foods so what you get with one bag is completely different than what you get with the next bag. This alone causes stomach and GI upsets in all but the hardiest dogs and cats.

I know that I had the same problem as you are having too when I fed the Farmers and that it stopped and never came back since I have never used any food but SD since.
When it is all said and done and your cats are on a 20 lb bag of Science Diet, you will be spending about $0.40 a feeding per cat with it. Compare that to the food you use now and in amount of days that you go through a bag of food.
It takes three weeks for a cat to metabolize enough Science Diet to see this change in their eating habits but once they are past the three weeks their consumption goes down and you spend less than you do now. The first outlay is more but you and the cats will reap the benefits or you can get your money back. 100% guaranteed.

I hope that before you bring new cats into your house they are also being tested for leukemia, FIP and FIV. You could run into some legal problems if you give away a cat for adoption that has one of these diseases and spreads it to another of their own pets and/or dies.
Protect yourself and the cats and get them tested.