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Wednesday, November 25, 2009

A Cat's Dietary Needs

Clearing out my inbox, Jodi poses this set of questions about feline nutrition.

why does it seem that so few veterinarians are interested in nutrition?? I believe a cat is a carnivore .Isnt an ideal diet one that consists of high qulity meat, very little carbohydrate, and no grain? My mothers cat has struvite crystals and bladder stones......all he has eaten is good quality canned food and very little dry. the special diet the vet wants him to eat is garbage!
Since when do cats eat corn? and wheat? and by prodcuts and artificial (and toxic) preservatives?

Isn't there a way to feed him and acidifying diet that has good quality nutrition? Even if this diet gets rid of his problem how can it be good for him?? He'll be free of crystals but malnourished!

Thank you for any help or resources you may have,


Well, Jodi, nutrition is actually much more complicated that it may first seem, and many veterinary schools don't emphasize this particular topic enough (in my opinion).  I have done a lot of personal research on this in the last year because I realized the failings in my own knowledge.

You have to realize that pet food is a bit of a compromise.  Until someone is able to create and successfully market a cat food that is made up of ground whole rodents and birds, we won't be 100% accurate in replicating a cat's natural food.  And truthfully, do we want to duplicate the natural conditions of cats?  Pet cats live far longer, healthier lives than wild ones, and that is in part due to good nutrition.

However, I concede that the current diets are not always ideal.  Recent research has suggested and supported the viewpoint that our feline friends should have a "catkins" diet.  This means high protein and low carbohydrates.  A few studies have shown that this helps regulate weight, lean muscle mass, and blood sugar levels better than the typical foods.  However, the only way you're going to get the right balance of protein and carbs is in canned food.  Canned foods are more expensive and more hassle to feed daily than dry foods.  In order to make a food maintain it's shape and consistency as a dry kibble, you have to have more carbohydrates than might otherwise be ideal.  This is most commonly and inexpensively achieved through the ingredients of corn, wheat, and rice.

Now the first thing to realize is that corn and wheat are NOT poor nutrition.  Ground corn is actually very nutritionally dense, and is not filler.  I have consulted with several independent veterinary nutritional specialists to come to this realization.  No, it's not a natural part of the diet of a wild cat, but I doubt you're going to feed such a diet. When you're ready to go to the pet store and buy mice, hamsters, and small lizards to give to your cat as it's food, then we can talk about the realities of a "natural" diet.

Along a similar line, by-products are NOT bad.  Here's the official definition used by the Association of American Feed Control Officials (AAFCO), the organization that determines the nutritional requirements of all pet foods sold in America.
The non-rendered, clean parts, other than meat, derived from slaughtered mammals. It includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth and hoofs.
Think about this for a minute.  In the wild, what do dogs and cats eat?  Do they eat only the muscle meat?  Nope.  They eat the entire animal, including organs and bones.  And that's exactly what by-products are! So you can in no way say that by-products are poor nutrition.  In fact, there are many important nutrients found in organs such as the liver that you can't find in muscle (what we normally term "meat").

Here are a few other probably little-known facts. 

AAFCO mandates minimal nutritional requirements in any pet food sold in the US, regardless of who manufactures it.  Now admittedly, the food company can meet these requirements by nutritional analysis rather than actually feeding it to pets.  Look on the label somewhere around the ingredients list.  If it says "tested" or words to that effect, then a nutritional analysis was made on pets actually fed the food;  "formulated" means a chemical analysis of the food was done without testing.  Testing the food is a better analysis of the quality than merely formulating it, though formulating can be acceptable if the company is good.

ALL cat foods currently on the US market will acidify the urine!  That is a legal requirement mandated by AAFCO.  Decades ago the incident rate of struvate crystals in cats was very high.  It was discovered that by acidifying the urine, we could help prevent formation of these crystals (which can lead to bladder infections and stones), and so it became a requirement of cat foods. However, there is another type of crystal, calcium oxalate, which will form in acidic urine!  And this type of stone is much harder to deal with than struvite.  So really, we traded a tendency for one kind of crystal for another one.

Crystal formation is also more complicated than merely the pH of the urine.  Many other things play a factor, including genetics, urine concentration, mineral intake, and so on.  There are some dogs and cats that will develop bladder stones despite the best diets and medications. 

So what can you do?  First, follow the vet's recommendations.  A pet with a tendency for these stones needs to be on a specific diet.  This may acidify the urine, but ideally should result in a moderate to slightly acidic pH.  If you get too acidic you can increase the risk of calcium oxalate stones.  You also want dilute urine.  This means that the food should be designed to promote drinking water (by slightly increasing salt content and therefore stimulating thirst) or by containing more water, such as in canned foods. 

I can assure you that by feeding these recommended diets the cat will NOT be malnourished.  We have many decades and millions upon millions of dollars worth of research to show that these diets give complete and balanced nutrition.  And it's not all done by food companies to promote their products.  Much of this data is from independent, government-sponsored, or university-sponsored research.  And even the data from the food manufacturers can't be discounted, as it is reviewed and studied by people outside of the food industry.  It's also in the manufacturers' best interest to have high-quality foods that promote healthy pets.

Hopefully this helps answer your questions, Jodi, and shows you some of the realities behind pet nutrition.

7 comments:

  1. Good answer Chris. I often have to explain to people why our "expensive unnatural" food is better suited to their animal's paricular needs than a natural raw (or worse, table scrap) diet. I was lucky enough to have worked in a game reserve in Africa and have seen the condition of some of the animals on their "natural" diet (even to the extent of examining a lion's teeth, which granted, didn't have much tartar buildup!) and what they don't realise is that most animals don't make it past the age of 10 and if they have a dietary problem, well, too bad. I might have to borrow some of your argument for the next consult!

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  2. Borrow away! Nutrition has become a new interest of mine over the last year, so I've been trying to study the topic more.

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  3. This is great Dr. Bern. Can I use it in our clinic newsletter? I will attribute it to you, etc. You can reach me at nutrition at stateroadah dot com. Thanks!
    Sheila Sherwin

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  4. By all means, please do, Sheila. Glad I can help out.

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  5. Thank you for explaining by products. How long is canned food safe to leave out. For instance, can I put out a can of food in the morning and my cat doesn't finish it until 8 hours later (If it hasn't dried out), will it make him sick? Also, one of my cat throws up about once a week after eating-I suspect it's the beef variety, but not always. Is beef a common alergen in cats?
    Thanks.

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  6. I haven't seen any specific data that says exactly how long food can be left out and still be safe. There is data in human medicine regarding deli meat and leftovers, and the time is extremely short (only a day or two if I recall properly). Eight hours shouldn't be a serious health risk. I definitely would get rid of the food before the next day.

    Beef is indeed a common allergen, but may not be the cause of the vomiting. Make sure to check with your vet if the vomiting is persistent.

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  7. Still not going to give my pets food with byproducts in it. Animals in the wild may eat the whole animal, but they DON'T eat factory-farmed animals raised in filthy conditions (you mentioned working on a pig farm).

    That said, I'm also not stupid enough to think I can prepare a balanced diet for another species without extensive veterinary nutrition training (or help from someone with such training), even if I had the time (which I don't).

    I'll stick to my Blue Buffalo kibble.

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