Does Mildew Grow on Dog Food?

Many pet food recalls have been a result of mycotoxin contamination.
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Is your dog a picky eater? Maybe, but it is also possible that he can sniff out mold and mildew in his kibbles that you are completely unaware of. Knowing what could be lurking in your dog’s food and how to store dog food properly could save you and your pet a lot of anguish.

Mold and Mildew Growth

According to the EPA, mildew is a generic term that refers to the flat growth habit of some molds. It is often distinguished from other molds by its powdery white or gray appearance. All molds are species of microscopic fungi that thrive on organic matter in moist, warm environments. Because dog food is organic matter, it is prone to mold and mildew, even though pet food manufacturers use measures to reduce how quickly this process will begin. Most dry dog food can be safely stored for many months in un-opened bags. Once a bag of food is opened, however, it is exposed to airborne fungal spores, moisture and light which will speed up the processes of decomposition, including mold growth.


If you see or smell mold on your dog’s food, obviously you should not feed it to him. Despite their dumpster-diving tendencies, dogs do not have cast-iron stomachs and often get sick from their poor choices in food. A bigger concern are mycotoxins found in dog food that has wheat, corn or soy that are contaminated with certain strains of molds. According to Ultra Bio-Logics, the mycotoxins aflatoxin, vomitoxin (also known as deoxynivalenol), fumonisin, zearalenone and ochratoxin have the most potential to cause problems with pet food. Symptoms of vomitoxin poisoning include severe vomiting and can cause death in dogs. Aflatoxins cause liver damage and are also linked to cancer. Fumonisin affects the liver, brain and cardiopulmonary system of animals. Zearalenone can cause reproductive issues in some animals, but its effects on dogs have not been widely studied. Ochratoxin affects animals’ kidneys. These substances are not usually detected by visual inspection or smell.

Pet Food Recalls

Mycotoxin contamination has resulted in several large-scale pet food recalls, including Nature’s Recipe in 1995, Doane Pet Care in 1998, Diamond in 2005, Menu Foods in 2007 and Diamond again in 2012. People were also affected during the 2012 Diamond contamination through handling pet food tainted with salmonella. The Food and Drug Administration does issue guidelines on the acceptable levels of mycotoxins that can be found in grains, but they do not monitor the manufacturing of pet foods as closely as food production for human consumption. Manufacturers now more closely monitor their products for contamination through periodic analysis of food samples.


Reduce your dog’s health risks by paying attention to manufacture and expiration dates on dog food bags, leaving the dog food in the bag once it is opened and storing the entire bag in an air-tight container. Cleanse scoops and food dishes daily with soap and water. Store dog food in a clean, moisture-free place, such as a pantry. Pay attention to signs of mold growth on your dog’s food or in the storage container and replace any food that is questionable. If your dog is suddenly reluctant to eat his food, stop feeding it to him. Often the most contaminated food is in the bottom of the bag and your dog is better able to detect the scent of bad food than you are. If your dog shows signs of lethargy, diarrhea, vomiting, seizures or panting after eating, consult a veterinarian as soon as possible and bring information or samples of the dog food that he last ate with you when you take him to the vet.