Reading Pet Food Expiry Dates: Best Before vs Use By
Date labels on pet food packaging are one of the most misunderstood aspects of animal nutrition, yet they carry real implications for both the safety and the nutritional value of what your pet eats. The distinction between "best before" and "use by" is not arbitrary — it reflects a meaningful difference in what happens to food after that date, and confusing the two can lead to feeding a pet food that is either needlessly discarded or genuinely unsafe.
The Difference Between Best Before and Use By
A use by date indicates a safety threshold. The manufacturer has determined, through stability testing, that the food is safe to consume up to that date when stored correctly. After a use by date, pathogenic bacteria may have multiplied to unsafe levels or other changes may have occurred that make the food genuinely hazardous. In human food, use by dates appear on products like raw meat, fish, and soft cheese — items with a direct microbial risk.
A best before date is a quality indicator, not a safety marker. Food past its best before date may have deteriorated in taste, texture, appearance, or nutritional content, but it is not necessarily dangerous. The manufacturer is saying that the product will be at its best up to this date — not that it becomes harmful immediately after.
In the context of pet food, most products carry a best before date. Wet food in tins and pouches, and dry kibble in sealed bags, are shelf-stable products whose primary risks past the date are quality degradation rather than sudden pathogenic contamination. However, this distinction does not mean best before dates are irrelevant, particularly for pet food where nutritional completeness matters for long-term health.
What Happens to Pet Food After the Best Before Date
The changes that occur in pet food after the best before date depend on the type of product and how it has been stored. For dry kibble, the most significant changes involve fat oxidation and vitamin degradation. Fats in the food continue to oxidise over time, producing rancid compounds that reduce palatability and can cause gastrointestinal upset. Fat-soluble vitamins including Vitamin E, which is often used as a natural preservative, deplete progressively, reducing their protective effect and their nutritional contribution.
For sealed wet food in tins, the situation is somewhat different. The canning process creates a sterile, anaerobic environment that is highly effective at preventing microbial growth. A tinned product that is undamaged and properly stored may remain microbiologically safe well past its best before date, though quality factors including colour, texture, and flavour will decline. Dented or damaged tins are a different matter — compromised packaging can allow contamination, and damaged tins should not be used regardless of date.
Pouched wet food, particularly foil-laminate pouches, is more susceptible to quality degradation than tinned equivalents and should be treated with more caution once the best before date has passed.
Where to Find Date Information on Packaging
Date information on pet food packaging is not always immediately obvious. On dry food bags, the best before date is typically printed on the back of the bag near the bottom, alongside the batch or lot code. On tins, it may be embossed or printed on the base of the tin. On pouches, it is usually printed on the back panel or on a side seam.
It is worth checking this date at the point of purchase, particularly when buying from discount retailers, online marketplaces with third-party sellers, or shops that may have slow stock turnover. A bag of food with only a few months remaining before its best before date will deteriorate more quickly after opening than a freshly dated bag, reducing the practical window in which you should feed it.
What the Date Does Not Tell You
Date labels reflect expected product quality and safety under the storage conditions the manufacturer specifies — typically cool, dry conditions in a sealed or resealed container. They do not account for poor storage, which can cause food to deteriorate far faster than the date would suggest. A bag stored in a hot garage or left open and exposed to humidity may be of very poor quality months before the printed date, while the same bag stored correctly may be in good condition at the date itself.
Date labels also do not reflect contamination events that occurred before or during manufacturing. A product well within its best before window can be the subject of a safety recall if contamination with bacteria, moulds, or foreign material occurred during production. This is why checking recall databases and batch codes is a separate and additional safety step, not a substitute for checking dates or vice versa.
Practical Guidelines for Pet Owners
For dry food, the general recommendation from most manufacturers and veterinary nutritionists is to use the food within six weeks of opening, irrespective of the printed best before date. After opening, the food is no longer in its sealed low-oxygen environment, and oxidation proceeds faster regardless of when the bag was manufactured.
- Check the best before date before purchasing and choose products with adequate shelf life remaining
- Store food correctly — sealed, cool, dry, and away from direct light — to reach the intended quality at the date
- Do not assume food is safe simply because it is within the best before date; check for changes in smell, appearance, or texture each time you open the container
- For opened wet food, refrigerate and use within the timeframe specified on the packaging, usually two to three days
- Discard any food that smells off, has changed colour significantly, or shows any mould growth regardless of date
When to Contact a Vet
If your pet has consumed food that you suspect was past its best quality — whether due to date, storage conditions, or obvious deterioration — and subsequently develops vomiting, diarrhoea, lethargy, or loss of appetite, contact your veterinarian. Most exposures to degraded food will cause at most mild digestive upset that resolves quickly, but more significant contamination can cause serious illness. Keeping the packaging with the batch code allows your vet and, if necessary, the relevant food safety authority to investigate further if multiple animals appear to be affected by the same product.