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Dog's Food

The Facts About Fat in Your Dog’s Food


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Do you keep food on your shelves for a long time? I suppose I probably do, because I’m one of those people who likes to stock up when thing are on sale. I might start re-thinking that approach, though, when it comes to my dog food. What I didn’t realize (although I suppose with 20/20 hindsight it makes a world of sense) is that just as soon as a food is made, it starts to change chemically – in other words, it’s going to degrade. The vitamins and the proteins are going to break down. That’s not great, but one of the big concerns is the fat in dog food.

Dogs need fats in their food. In fact, a lot of dog food companies now add DHA (docosahexaenoic acid) to their puppy formulations, because it is known to help puppies learn more quickly, and retain more of what they learn. But the question is, can DHA last long enough, and hold up well enough, under storage, to do much good? When it comes to dog food, fats are the most fragile nutrients, and they are what limits the shelf life. In fact, if stored for too long, the fat can turn rancid, and that can lead to numerous health problems.

Why Dogs Need Fat

Fat provides concentrated energy for your dog, keeps his skin supple and his hair healthy, protects his immune function, contributes to cell regeneration, regulates the inflammatory process, and aids in prenatal development for puppies. That, in a nutshell, is why dogs need fat.

Now, the problem is that many dog foods fail to deliver all the categories of fats that dogs need. The types and quantities of dietary fat can vary considerably from brand to brand, and then of course there’s that nasty problem of deterioration and rancidity again. Fortunately, if we put a little extra effort into our dogs’ diet, these problems can be overcome.

The Problems

Before dogs were domesticated, they would have gotten a full range of the fats that they needed, because they would eat every part of the prey animal that they hunted. From muscle meat, dogs would get MUFAs (monounsaturated fats), SFAs (saturated fats) and PUFAs (polyunsaturated fats). They would also get MUFAs from bone marrow and organ fat, SFAs from storage fat, and PUFAs from organ fat, eyes and brains. Eyes and brains also contain DHA.

The NRC (Nutrient Research) Council is periodically re-working what it considers to be essential nutrients for dogs, and they are always adding, never removing, nutrients from the list. As long ago as 2006, the NRC added DHA to its list of essential nutrients for dogs, and yet it is still not present in many dog foods. But then, we’re back to the problem of rancidity – the more DHA a dog food contains, the more likely it is to go rancid. Some fats deteriorate more quickly than others, and DHA, unfortunately is one of them.

When fat turns rancid, it is transformed from a substance that is beneficial to dogs into one that is toxic because it produces ketones and aldehydes. This can result in macular degeneration, diarrhea, arthritis, heart problem, liver failure, cell damage and even death. So you really want to avoid feeding rancid fat to your dog. Remember, all the omega-3 fats are highly fragile, and the long-chain ones like DHA and EPA are even more fragile than most.

The Goal, and Why We’re Not There Yet

The scientific evidence doesn’t lie – dogs who eat a fat-rich diet, especially a diet that contains a proper balance of omega 3 and omega-6 fats, are not only healthier, they also display higher intelligence than dog who do not get the right amount of fats. The trouble is that pet food regulators like AAFCO (Association of American Feed Control Officials) do not require pet food manufacturers to provide the agreed upon balance of fats that pet nutritionists tell us our dogs should be receiving. And as I pointed out in How Good is Your Dog’s Food, it doesn’t take much for a dog food to be labeled “complete and balanced.”

Some manufacturers of dog food have recognized the benefits of fatty acids, even though not all of them are needed for a dog food to be called “complete and balanced,” and are including fish oil (one of the best sources of DHA) in their products. You won’t usually find fish oil in store brands, though, so you may need to go with a premium brand or add a supplement to your dog’s food.

In fact, supplementing is probably the better way to go. That’s because most commercial foods, even the premium ones, might not get the balance right, and again because of the problem of rancidity if stored too long (combined the with natural reluctance of people to throw out part of a really expensive bag of dog food just on the suspicion that it might have gone off. This could be one reason why even makers of “complete and balanced” dog food often don’t include much DHA – it just doesn’t stand up in food that’s meant to be sitting on store shelves and in stockrooms, sometimes for more than a year, and then taken home and left open in someone’s home for a number of weeks. Some manufacturers include no DHA at all, because they know that no DHA is actually better for a dog than rancid DHA.

As to companies that do include DHA, when they do quality testing, purportedly to ensure that DHA and other fatty acids hold up after manufacturing, do the tests either at the time of manufacturing, or very shortly afterward – in other words, not in real-life conditions. So the results of the quality tests are seriously skewed.

How Can Your Dog Get the Fats He Needs?

If you want to go with a premium dog food that contains DHA and other fish oils, check your best before dates very carefully, and always err on the side of caution. I think, though, that the better course of action would be to buy foods that do not contain those ingredients, and find other ways of adding them to your dog’s diet.


One of the very best ways to add DHA and EPA is simply to give your dog a tin of sardines once a week. You could also use a fish oil supplement, but sardines deliver other benefits as well – they contain little mercury, lots of protein, a full range of trace minerals and vitamins as well as anti-oxidants. And they’re sustainable! Also, the DHA in sardines are of the phospholipid and triglyceride forms, and are more stable and absorbable than the ethyl ester type that most fish oils contain. Accordingly, they are believed to be better for cancer prevention and improving brain function.

Feed sardines that are packed in water without salt. If your dog refuses to eat sardines, or if you can’t stand the smell, you could substitute human grade krill or fish oil in gel caps, but don’t overdo it – no more than a gram a day for dogs up to 45 pounds, and not much more for larger dogs.

If you like, you could also substitute canned wild salmon (but not raw salmon or trout because it could contain bacteria that are lethal to dogs) or oysters as a substitute for the sardines. You’ll probably find the smell considerably less offensive, and most dogs find these treats quite pleasing.

There are other things you can do, too, if you’re going to continue feeding dry food to your dog. Some of the following suggestions will help you to choose better foods, while others will help you to ensure that the food stays in good condition until your dog has consumed all of it.

Check Out the “Produced On” Date

Some pet food manufacturers will print both a “best before” and a “produced on” date on their labeling, most just go with the “best before” date. If you really want to know how fresh your dog’s food is, you should know when it’s made. So, give the manufacturer a call or hoot them an email, and ask what the product’s shelf life. If they tell you it’s 12 months, for example, then add 365 days to the “best before” date, and you’ll know when the food was made.

Buy Fresher Food

Fresh dog foods are becoming more and more popular, and you can buy them in mot pet food stores in the refrigerated section. Choose chicken-based products and make sure that the stock is rotated regularly. Don’t be fooled by exotic meats – they might not get rotated that often.

Check to See if Your Dog’s Food Has Synthetic or Natural Preservatives

Often, we think that “natural” invariably means “better,” but there is a tradeoff. Natural preservatives may be somewhat safer, but synthetic preservatives will prevent rancidity for longer. So if you’re going to be keeping the food close to its “best before” date, I’d go with a food that has a synthetic preservative. I’m pretty sure that dogs will be far less harmed that way than they could be if the fats in the food go rancid.

Choose the Food that Has the Longest Shelf Life

This means, generally, no fish oils. It also means that food in foil bags is better than food in plastic or paper. Plastic and paper will keep out things like bugs and moisture, but they’re not going to work all that well for oxygen. So, if you’re going to buy foods that contain fish oils, buy them in foil bags. Yes, I know that’s not all that “green,” but when it comes to my dogs, I don’t care – my carbon footprint is going to be the least of my concerns. Of course unless you really need to store food for a long time, you should be able to avoid the need for foil bags.

Freeze Your Dog’s Food

Freezing won’t do any harm, and it will forestall rancidity a fair bit. If freezing is not practical, make sure that the food is stored somewhere that’s cool and dry. If you are using a food container, leave the food in the bag it came in, and then put the bag in the food container

Do the Smell Test

If your dog’s food smells funny, or if he seems to think it smells funny, toss it. You have your sense of smell for several reasons, and one of those reasons is to tip you off to something that shouldn’t be eaten.

Avoid Jugs of Fish Oil

If you’ve ever gone to a dog show, you’ve probably seen people offering fish oil for sale in clear, gallon jugs. Don’t buy it. If you have a lot of dogs, or if you have big dogs like I have, you might feel tempted by the low price per serving. The problem is that plastic jugs don’t offer much protection against air, and none at all against light, both of which cause oxidation – rancidity. Also, you’ll probably have no idea when the products were made, or how they’ve been stored. As I’ve pointed out a couple of times already, no DHA is better for your dog than rancid DHA

The Final Word

I certainly learned a lot researching this post, and I hope it’s been helpful to you as well. I’m not going to make radical changes to my feeding regime – I’m still going to continue to free feed, despite the objections I’ve heard, and I’m still going to use a decent quality dog food, but I’m not going to break the bank buying the expensive stuff. I will be adding a fish oil supplement to their diets, though, most likely in the form of sardines if they’ll eat them – I loathe the smell, but hey, Janice and Leroy a

About the Author Ash

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