Yes. EPA and DHA, two long-chain omega-3 fatty acids, can decline in dry dog food during storage. But there is no universal loss rate or deadline that applies to every bag. The useful distinction is between the amount added during manufacturing, the amount measured in finished food, and the amount remaining later. Laboratory studies show why storage deserves attention; they do not establish that all kibble becomes nutritionally inadequate or that your dog needs an extra supplement. 1 3
Think in three stages, not one ingredient claim
Nara's useful mental model is added → measured → retained.
“Contains fish oil” answers an ingredient question. It does not, on its own, answer how much EPA and DHA are in a serving or how those amounts change over time. Equally, a laboratory finding of oxidation is not automatically a finding of disease in dogs.
For an owner comparing foods, this changes the question from “Is fish oil on the label?” to “What does the manufacturer know about the finished food, including its shelf life?” That is a more useful question than trying to infer nutritional quality from the food format alone.
Start with the storage choices you can control
The FDA recommends keeping dry pet food in a cool, dry place below 80°F, approximately 27°C. Keep the original bag: besides its storage role, it preserves the lot number, best-by date and other details needed if there is a problem. When using an outer storage container, the FDA prefers placing the bag inside it. Wash and thoroughly dry storage containers between bags rather than leaving old crumbs and fat behind. 6
Nara's practical interpretation is to follow the specific manufacturer's after-opening instructions and choose a package size that makes those instructions realistic. A bulk bag is not automatically the best purchase when one small dog takes a long time to finish it.
If the label is unclear, ask the company how its after-opening guidance differs from the unopened best-by date. These studies do not justify inventing a universal four-week or six-week limit.
What the new 15-month experiment found
A study published on 16 September 2026 compared ten lipid sources on grain-inclusive and grain-free extruded kibble, with or without one antioxidant blend. During 15 months at 22°C and 50% relative humidity, mean EPA and DHA concentrations across the experimental treatments fell 98.7% and 77.9%, respectively. Lipid source strongly influenced oxidative stability; the tested antioxidant blend did not consistently prevent deterioration. 1
Those striking percentages describe deliberately constructed, lipid-coated experimental foods over long storage. They are not a measured loss rate for every commercial product, nor a prediction for a bag opened last month. The study investigated food chemistry, not illness or lifespan in dogs.
The relevant lesson is formulation-specific preservation, not “all kibble loses all its omega-3.”
Does extrusion destroy omega-3 before storage even begins?
No. Substantial DHA can survive extrusion.
In a commercial-scale study of kibble containing DHA-rich algal biomass, researchers tested 21 finished-food samples and recovered about 85% of the DHA expected from the amount added. This was an analytical-method validation study, not a comparison of every manufacturing process or a feeding trial. It also involved a particular formulation, so it cannot establish that all DHA sources behave alike. 2
Nevertheless, it is a useful counterexample to “extrusion destroys everything.” The measured recovery after manufacturing and the amount retained months later answer different questions.
| Stage | Useful evidence | What it does not establish |
|---|---|---|
| Manufacturing | Measurement in finished kibble | Retention throughout storage |
| Storage | Repeated chemical measurements over time | A universal decline for other products |
| Feeding | Clinical outcomes in dogs | Not assessed by the chemistry experiments discussed here |
What studies of commercial bags add
A 2025 pilot examined six commercial dry dog foods, with three packages of each sampled at opening, three months and six months under 20°C and 40% relative humidity. Fatty-acid composition and antioxidant measurements changed, but not every measure followed a simple downward line. 3
That is closer to an owner-storage question than a specially coated experimental kibble, but six products under one set of conditions cannot establish how every household's food changes. The researchers did not demonstrate that those chemical changes caused disease.
An earlier four-food study also cautions against a universal deterioration curve. After seven months, measures of oxidative stability improved in some products and worsened in others. Daily opening was not simulated, and the authors described the overall storage effect as moderate. 4
The combined message is variability, not reassurance that storage never matters.
Are antioxidants useless, then?
No. A disappointing result for one blend does not invalidate every antioxidant strategy.
In a separate dog-food experiment, some natural antioxidant treatments reduced oxidation and helped preserve EPA and DHA. However, the test ran for 12 days at 55°C: useful for comparing formulations under accelerated conditions, not equivalent to an opened bag in a kitchen. 5
An ingredient list naming an antioxidant is therefore not enough to calculate remaining EPA or DHA. Conversely, these experiments are not instructions to mix antioxidant powders into food. They concern how manufacturers design and test formulations.
What to ask when omega-3 content matters to you
Nara's interpretation is to ask for EPA and DHA amounts, rather than treating a fish ingredient or an unspecified omega-3 claim as the answer. Ask whether the company's information refers to the finished food and what stability testing supports its storage guidance.
A manufacturer may not publish every stability result. That leaves uncertainty; it is not proof that the food has failed.
The research reviewed here does not establish a need for extra fish oil, a replacement diet or a particular supplement dose. Nor does it rank kibble against fresh food for long-term health. For that separate question, see Is gently cooked dog food healthier than kibble?.
Evidence confidence
Moderate for the conclusion that omega-3 content and fat chemistry can change during storage; low for predicting the amount lost from an individual bag. These are direct dog-food experiments, not evidence that a measured chemical change causes a specific clinical outcome. No health or longevity benefit is assigned to changing food format on this basis.
Sources
Commercial context matters: the 2026 paper includes Champion Petfoods and Kemin affiliations. The algal-DHA study was sponsored by Alltech and included Alltech employees. The 2025 commercial-food pilot reported no external funding or conflicts of interest.
- Rankovic A, Shoveller AK, Saunders-Blades J, et al. Lipid source and kibble matrix determine oxidative stability and n-3 fatty acid loss in coated extruded dog food. Journal of Animal Science. 2026. doi:10.1093/jas/skag297.
- Dillon GP, Cardinall C, Keegan JD, et al. The Analysis of Docosahexaenoic Acid (DHA) in Dried Dog Food Enriched with an Aurantiochytrium limacinum Biomass. Journal of AOAC International. 2021;104(1):68–77. Matrix-extension validation and verification of AOAC Method 996.06. doi:10.1093/jaoacint/qsaa097.
- Kępińska-Pacelik J, Biel W, Witkowicz R, et al. Changes in the Fatty Acid Composition and Antioxidant Properties in Mono-Protein Commercial Dry Dog Foods During Storage. Molecules. 2025;30(17):3524. doi:10.3390/molecules30173524.
- Hołda K, Głogowski R. Selected quality properties of lipid fraction and oxidative stability of dry dog foods under typical storage conditions. Journal of Thermal Analysis and Calorimetry. 2016;126:91–96. doi:10.1007/s10973-016-5543-2.
- Glodde F, Günal M, Kinsel ME, AbuGhazaleh A. Effects of Natural Antioxidants on The Stability of Omega-3 Fatty Acids in Dog Food. Journal of Veterinary Research. 2018;62(1):103–108. PMID:29978134.
- U.S. Food and Drug Administration. Proper Storage of Pet Food & Treats. Accessed 25 September 2026.