How Long Does Kibble Last?

Post At A Glance

What’s more expensive … your dog’s kibble or the bag it comes in?

Pet food companies invest heavily in packaging. Packaging with compelling pictures and benefits helps make sales. And packaging is also critical to the safety of the kibble. Experts with PhDs develop and test your dog’s kibble packaging so it can sit on the shelf for months or years and still hold much of its nutrition. And if they get it wrong, dogs get sick.

But their job ends when you open up that bag of kibble. As soon as you open it, the food changes quickly. And those changes can be toxic to your dog.

So how long does that bag of kibble really last?

How Long Does Kibble Last?

Kibble lasts only 2-3 weeks once the bag is opened. That’s far shorter than the “Best Before” date on the bag … which is usually at least a year. But that date applies to unopened bags of food. Once opened, food loses its nutritional value and the fats begin to oxidize and go rancid. 

And every time the bag is opened, air gets in and the problem gets worse. Here’s why …

How They Make Dog Food Last A Year

The main reason kibble is heated and dried is to remove the moisture from the food. Moisture is the enemy of any food that needs to sit on a shelf for months or years … because moisture breeds bacteria. So most kibbles contain only about 10% moisture.

Once the kibble is dried, the packaging is critical to the stability of the food. If air got into the food on the shelf, it would become oxidized. Oxidation happens when the chemicals in the food come into direct contact with oxygen. Oxidation lowers the nutritional value of the food … and can also cause toxic mold and bacteria to grow.

The most sinister result of oxidation is how it damages the fats in the food. But modern-day packaging has a grease barrier. The barrier usually contains a synthetic antioxidant to prevent the fats from oxidizing and becoming rancid. So with the proper packaging in place, the pet food manufacturer can send that food out on pallets … and it can sit on the shelf with a “Best Before” date so you feel safe knowing the food you buy your dog isn’t spoiled.


While AAFCO requires pet food companies to put a “Best Before” date on your food, they don’t have to say when the food was manufactured. So you don’t know how long the food has been sitting on the shelf before you buy it.

But because the packaging is such an important part of keeping your dog’s food safe from the harmful effects of oxygen, what happens when you open that bag?

Why Fats In Kibble Go Rancid Fast

The minute you open your dog’s bag of kibble, air gets in and the oxidation process begins. And every time you open the bag, the amount of oxidation increases, along with the health risks. The fats and oils in the food are very susceptible to oxidation … so every time you open the bag, the fat particles break down into smaller compounds such as malondialdehyde, (a marker of cancer risk), and the fat becomes rancid.

The Problem With Rancid Fats

Here’s why you don’t want your dog to eat rancid fats.

  1. Rancid fats can destroy vitamins, which can lead to vitamin deficiency. Most dogs today are vitamin D deficient.
  2. In lab studies, dogs and other mammals suffered vitamin, fat and protein deficiencies when they were fed diets with rancid fats.
  3. Rancid fats have been linked to many other health issues … including malnutrition, hair loss, diarrhea, liver and kidney disease, reproductive problems and even cancer and death.

So it’s very important to prevent your dog’s food from oxidation.

RELATED: Dogs with vitamin D deficiency are at risk for cancer … 

What Fats Are In Kibble?

There are many types of fats and they’re divided into the number of carbon bonds they contain. And the more carbon bonds the fat contains, the more quickly it will oxidize.

  • Saturated Fats, like those found in beef, contain no carbon bond. So they’re not as unstable as other fats.
  • Monounsaturated Fats contain one double bond, meaning they oxidize more easily. Olive oil is an example of a monounsaturated fat. But the amount of oxidation isn’t nearly as much as it is in PUFAs, or polyunsaturated fats.
  • PUFAs, as their name implies, contain several carbon bonds. Chicken fat contains PUFAs, so foods with chicken or poultry fat are much more likely to oxidize than those with beef.

The fats with the most bonds are DHA and EPA … the fats found in fish oils.

Avoid Kibble With Fish Oil

One of the most dangerous trends in the pet food industry today is adding fish oil to kibble. Fish oil is extremely unstable. So even if it’s not oxidized and rancid right after the kibble is made … it will become rancid extremely quickly once the bag is opened and your dog’s health will be at risk.

Never buy kibble with fish oil added. If you want to give your dog fish oil, buy it separately and add it to his diet. But never feed him a kibble with fish oil already in it. It’s highly likely to be rancid.

RELATED: Learn why fish oil can be bad for your dog …  

Antioxidants In Kibble

Pet food manufacturers know about the problems with oxidation. So they use antioxidants to slow down the rate of oxidation. They add antioxidants to your dog’s kibble in two forms:

  1. Antioxidants that your dog’s cells can use to protect against the free radical damage from rancid fat.
  2. Antioxidants your dog can’t use … but that help preserve the food. If an antioxidant is used, AAFCO requires the pet food company to use the common name of the antioxidant, along with the fact that it’s used as a preservative. This will show up on the ingredient list next to the preservative name … like “Sorbic Acid (used as a preservative).”

Antioxidants can be natural or synthetic. And the type of antioxidant in your dog’s food really matters.

Synthetic Preservatives In Kibble

Synthetic antioxidants are a controversial addition to pet foods. Some better brands have stopped using them because of their impact on health. There are four common synthetic antioxidants in kibble.


Ethoxyquin keeps pet food fresh … but it’s also a pesticide! It’s not approved as a direct food additive in foods made for human consumption …. but it’s still in pet foods. The FDA allowable amount in human foods is .5 to 5 ppm but in pet foods it’s 150 ppm.

Ethoxyquin is a controversial additive. Pet owners have been reporting liver and health issues to the FDA for years. The FDA asked Monsanto, one of the major manufacturers of ethoxyquin to study the food and they reported that higher levels could change liver enzymes.

But an independent report from the EPA claims that dogs are more susceptible to ethoxyquin toxicity than the rats Monsanto used in their study. They found elevated liver enzymes at just 4 mg/kg/day over a 90 day feeding period. That’s equivalent to 160ppm … just barely above the upper limits allowed in pet foods. More importantly, the cumulative effects of eating ethoxyquin for more than 90 days wasn’t considered in any of the studies.

And it’s not always noted on the ingredient list …

Ethoxyquin In Fish Meal
If your dog’s food contains fish meal, it contains ethoxyquin. Ethoxyquin is required by law when transporting fish meals. But because the ethoxyquin isn’t added directly to the pet food, AAFCO doesn’t require the manufacturer to put it on the ingredient list. Ethoxyquin can also be added to poultry meals.

Pet food manufacturers can apply for a special permit that allows them to use natural preservatives instead, so it’s best to ask the manufacturer directly for proof. If they don’t provide proof of natural antioxidants, don’t buy the food).


Both BHA and BHT are artificial preservatives that have been linked to cancer in lab animals. BHT is also suspected to cause developmental defects and thyroid changes.


TBHQ, or tertiary butylhydrquinone, is an antioxidant derived from butane. It’s also used to make varnishes and paints. TBHQ has been found to cause stomach tumors and it’s also been linked to many other forms of cancer.

RELATED: Read more about synthetic additives in pet foods …

Natural Preservatives In Kibble

Natural preservatives, such as vitamin E (which is usually called mixed tocopherols) and vitamin C (normally called ascorbic acid) are used in better quality foods. But while natural preservatives are less toxic than their synthetic counterparts, they don’t offer the same shelf life. And while they’re less toxic, not all “natural” preservatives are, well, natural!

Some of the more common natural antioxidants include:

Mixed Tocopherols

These are technically synthetic as they’re isomers of vitamin E extracted from vegetable oils and restaurant grease. The most effective tocopherol is gamma-tocopherol, which is derived from cereal grains

Rosemary Extract

Rosemary extract is the oily residue derived from the leaves of the rosemary plant. It prevents the oxidation of fats and protects flavors.

Most industrial plants use solvents such as acetone, hexane or methanol to extract the oil. Rosemary extract is added to fat as a blend or premix, which can also contain mixed tocopherols, citric acid, emulsifiers and a vegetable oil carrier.

Citric Acid

This is produced by the fermentation of crude sugars. Citric acid is generally recognized as safe (GRAS) and is used In both the human and pet food industry.

Instead of using synthetic vitamin E and C or rosemary extract, some pet foods will choose to use fruits containing citric acid, such as cranberries, blueberries or apples to defend against oxidation.

5 Tips To Keep Kibble As Safe As Possible 

Use these 5 tips to make sure your dog is getting the best nutrition possible from his kibble.

Know How Your Dog’s Kibble Is Preserved

If you’re looking for food-based preservatives instead of synthetic chemicals and vitamins … good for you! But be aware that your food won’t last as long.

Know What Fat’s In The Kibble

How long your pet food lasts once it’s opened depends on where the fats are from. If your dog’s kibble is beef, then you need to use the bag up within 3 weeks. But if it’s chicken or other poultry, the PUFAs will degrade faster and you should use the food within 2 weeks of opening.

Don’t Buy Big Bags Of Food

It’s true that larger bags of food will cost you less, but your dog needs to get through that bag in 2 to 3 weeks before it goes rancid.

Don’t Buy Kibble With Fish Oil Or Omega-3 Fats Added

Fats from fish and fish oil oxidize very quickly. If you must feed a food with fish, use it up within a week for best results.
RELATED: The ultimate guide to balancing fats for your dog …

Never Take Your Kibble Out Of The Package

Remember, most pet food makers spend more on the package than the contents, and that bag is designed to keep oxygen out. If you must keep your food in a plastic bin, put the whole bag in the bin … then squeeze as much air out of it as you can and seal it with a clip.


Gaweł S et al. [Malondialdehyde (MDA) as a lipid peroxidation marker]. Wiad Lek. 2004;57(9-10):453-5. Polish.

Pavcek PL, Shull GM. Inactivation of biotin by rancid fatsJournal of Biological Chemistry. 1942;146(2):351-5.

Hewitt, E. A. McCay’s Nutrition of the Dog. Iowa State University Veterinarian. Vol. 7: Iss.2, Article 5.

Quackenbush FW. Toxicity of rancid fats. Journal of American Oil Chemists’ Society. 1945;22(12):336-8.

Greenberg SM, Frazer AC, Roberts B. Some factors affecting the growth and development of rats fed rancid fats. The Journal of Nutrition. 1953;50(4):421-40.

What is TBHQ … and is it safe for your dog. Dog Food Advisor. 

Najjar S. Health effects of rancid fatNutrition Nuts and Bolts. 2012. 

Gharavi, Negar, et al. tert-Butylhydroquinone is a novel aryl hydrocarbon receptor ligand. Drug Metab Dispos. 2005 Mar;33(3):365-72. 


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