This information is provided by Provet for educational purposes only.
You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.
We often talk about foods going "off" and becoming rancid - but what does rancidity mean ?
Food goes rancid when fats and oils in the food undergo oxidation through exposure to the air. This process creates chemical substances including aldehydes, peroxides, hydroperoxides and free radicals . These make the food smell and taste unpleasant , and they can also be harmful to the body. So, pet foods that are "off" should never be allowed to be eaten by animals.
Food sealed in a vacuum eg canned pet foods will not go rancid for a long time - unless the seal is broken. Dry foods are sprayed with oils and this will go rancid quicker - so the shelf life of dry foods is shorter than for canned foods. The approximate shelf-life for canned food is 24 months; for dry foods 12-18 months....but each product has it's own manufacturers recommendations. Pet foods should be stored in a cool environment and foods kept in hot conditions will go rancid much quicker.
Updated October 2013