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Pet Food Contamination: Aflatoxin, Molds, and Melamine

As a companion to the guest post I wrote on the basics of cat and dog nutrition over on PawDiet, (I promise I’m not abandoning our ABCs, and K will be my next post!), today we’re going to cover the touchy topic of pet food contamination.

If you haven’t had a chance to check out PawDiet, take a peek at the Food Finder and the widgets page.  The ability to find food based on multiple criteria is essential for picking the right diet for your pet!

What is so scary about packaged pet foods?

Pet Food Contamination
Villainous Pet Food!

This is a question bouncing around in people’s heads a lot lately, especially considering the food recall in 2007 and all of the buzz around switching to grain-free or raw-based diets.

There are a lot of factors that influence the quality of packaged pet food extending past the manufacturer. Ingredients shipped from distributors can become contaminated, storage of foods at the store (and at home) can affect food quality, and there are some toxins that the FDA doesn’t completely regulate. The contaminants we are going to cover today include:

  • Molds such as aflatoxin and tremorgenic mycotoxins
  • Melamine

Bacterial infection is an expansive topic and needs an article of its own! However, bacterial contamination is a very common type of animal food contamination.

In many cases, pet food contamination may not be directly related to the manufacturer itself, but instead a breakdown in one of many pieces in a chain of events that ends up affecting your animal.

Melamine – what happened in 2007

Melamine pet food contaminaion
A magic eraser made from melamine!
(No, magic erasers won’t kill your pet in the same way)

Melamine is a chemical used in the production of several non-edible products such as plastics and resin.  When added to wheat gluten, melamine can falsely increase the protein content when subjected to laboratory tests.  While not approved for use in any food, some companies will illegally add melamine to wheat gluten in order to falsely bump up the reported protein content of a product.

In 2007, a Chinese plant-product processor, a Chinese food product exporter, and an American food product supply company entered a contract together. From this contract, the US imported 800 tons of melamine-contaminated wheat products. When a pet food manufacturer reported several linked illnesses and deaths in the pet community, the supply companies were all brought up on federal charges.

How it’s different now:

FDA’s response was to develop an initiative called PETNet, which is a web-based network that allows for quick reporting and communication regarding illness outbreaks and pet food contamination between federal and state levels, previously a process that did not have good standards of communication.

Melamine has a wide margin of safety (meaning smaller ingestions cause fewer signs). However, the buildup of melamine in small amounts over a long period of time (called chronic exposure) causes the formation of crystals in the kidneys in both animals and humans.

The crystals lead to urinary problems, kidney stones, and eventually kidney failure.  Before everyone who has had an animal in kidney failure runs to report their pet food, this type of pet food contamination is not very common.  Due to increased regulation of food products on part of the FDA and increased awareness of melamine in the food industry, the risk of this happening is very low.  It is still a good idea to keep up-to-date on current pet product recalls through the FDA.

Aflatoxin and other molds

Pet food contamination: aflatoxin

Certain species of Aspergillus fungi (aka, a mold) produce aflatoxin as a toxic byproduct.  While many molds tend to be tremorgenic  (meaning they cause tremors and seizures), aflatoxin directly affects the liver.

These species of molds thrive in warm weather and moist grain conditions.  They are common enough in grain storage that the FDA has reported “acceptable” levels of aflatoxin in food-based products.  As you can see, the “acceptable” levels are HIGHER for food for animal consumption than for food for human consumption.

It is not a well-kept secret that pet food companies often invest in cheaper ingredients for their pet foods. Food that has NOT passed the qualification for human consumption sometimes finds its way into pet food for animal consumption.  While the current claim is that these levels of aflatoxin in pet food are not high enough to risk the health of the animal, there is not a lot of documentation on the long-term effects of chronic exposure in pets.

Acute exposure tends to occur when improper storage leads to acute contamination that slips through the cracks of the food control process (again not a common occurrence)

Signs related to aflatoxicosis start with tummy upset and progress:

  • Vomiting
  • Diarrhea
  • Unwillingness to eat
  • Dark, tarry stools from digested blood (melena)
  • Stomach pain
  • Bloody diarrhea
  • The buildup of fluid in the stomach (abdominal effusion)
  • Increases in thirst and urination
  • Dehydration and other electrolyte imbalances
  • Increases in liver enzymes, liver damage, and liver failure
  • Coagulopathy (excess bleeding)
  • Brain damage or malfunction
  • Death

As these signs are common among all toxins that cause damage to the liver, it can be very difficult to tie an affected animal to a contaminated food source.  If at any point you suspect that your pet ingested contaminated food and died as a result, insist upon a necropsy. Have samples kept of both your pet’s liver and the contents of your pet’s stomach. Bag up several samples of the food from home for laboratory testing (use gloves!).  Then, report everything to the FDA. 

Alternative to testing through the FDA (which they may or may not offer), you can have your vet send the samples off to a diagnostic testing lab for analysis.


There is no antidote for aflatoxin.  We treat animals supportively to help protect the liver and alleviate signs:

  • IV fluids to support hydration
  • Vitamin K supplements to prevent coagulopathy
  • Drugs to replace the loss of antioxidants and prevent vomiting
  • Liver protectants

As is often the case,  with sudden-onset liver failure, these cases can be difficult to treat and may end up being fatal.

Tremorgenic mycotoxins cause vastly different signs


In comparison to aflatoxin’s tendency to contaminate food during production, other molds grow after purchase. Improperly stored food may grow mold, leading to toxicosis (shout-out to Doctor Schell who authored this tox brief – she is one heck of a fun person and has led an interesting life). This is something that also affects animals who ingest trash, compost, or human food that is past expiration.

Signs of ingestion include:

  • Vomiting
  • Stumbling
  • Changes in heart rhythm and rate
  • Twitching
  • Tremors
  • Seizures
  • Death

Depending on how alert you are to the fact that your dog has ingested a moldy substance, treatments can vary:

Pets who ingest mycotoxins often do well if they receive treatment in time.  These animals require veterinary care, so keep the number to animal poison control handy. Alternatively, notify your local or emergency vet if you suspect exposure.

Prevent pet food contamination

As always, prevention is key to keeping your pet healthy. There are several changes you can make at home to reduce the likelihood of your pet eating spoiled or moldy foods:

  • Always check the expiration date on foods you feed to your pets.
  • Never feed anything that smells “off” or “funny”.
  • Store dry food in an air-tight plastic container with a lid.
    • Write the food’s expiration date on a piece of masking tape and tape it to the top of the lid.  Disposed of any expired food.
  • Cap and date opened cans of unused wet food.  Store them in the fridge, and toss them after 2-3 days.
  • Toss all cans of expired, unopened pet food.
  • Don’t keep food in the garage, or outside.
  • Invest in a  trash can with a lock, or get a lid-lock.
  • Throw away spoiled or moldy food in the outside trash can, and do not keep bags with moldy food inside.

Happy eating!

50 thoughts on “Pet Food Contamination: Aflatoxin, Molds, and Melamine

  • Great, usable information – I really appreciate this article! You’ve delivered educational content that all pet parents should read!

  • Great post! This is so important! We go through our pet food regularly and make sure it’s not outdated. I also carefully check it before feeding, too!

    • It’s a good thing, too! I’m surprised at the number of people that buy bags of food and just leave them sitting around forever!

  • Really useful information! I was familiar with the dangers of aflatoxins but learned some new stuff about melamine for sure. Thanks for sharing.

    • Hopefully I will be able to expand on the topic of food a little more once I’m done with the ABCs! I’m glad you stopped by!

  • We have to buy such small bags the food doesn’t usually have a chance to go bad. Big bags would be more cost efficient but it would spoil before we could use it all.

  • Interesting post – thanks! The quality and contamination risk with commercial foods is one reason why we feed our cats a raw diet – prepared at home and adhering to strict hygiene standards.

    • Raw diets are great. Though they have their drawbacks too which I will be posting on later, but strict hygiene standards eliminate a lot of the risks.

  • Yuck, pretty scary stuff. Ted’s little, so I buy smaller bags and store food in a plastic container.

    • Buying smaller bags seems to be a trend too! A good idea to keep from having more food than you can use!

  • It’s really scary how pet food can be contaminated. I try to feed my kitties high-quality food, but even that can be contaminated. We all have to be aware of the recalls and be mindful of what we’re feeding our babies.

    • Yes! Watching those recalls is important! Even the best of companies can have errors or accidents.

  • Pet food contamination happens way more often than people think. Great post with excellent information!

  • What great information you have provided here! I will be bookmarking this so I can refer to it again later. Thank you!

  • Great information. I worked on water purification for a while a few years ago and so scary what can contaminate food and water. Those toxins can be so bad for dogs.

    • Yes, aflatoxin is one of the nasty ones! It certainly is enough to make me wary.

  • Thanks for sharing this information. There’s so much to know and it’s so important to be vigilant!

  • I’m still angry over the melamine issue and don’t think the companies faced fair repercussions. However, there are so many smaller companies making pet food now – using human grade ingredients and in Canada at human-grade (and inspected) manufacturing plants, which makes me a little more confident. The food industry here is heavily regulated and meeting human food plant level inspections (voluntarily) is good PR.

    • I agree, I wish the punishments had been harsher. I would like to see the switch to all companies being required to use human-grade foods. Something to strive for, maybe! 🙂

  • I’m still angry over the melamine issue and don’t think the companies faced fair repercussions. However, there are so many smaller companies making pet food now – using human grade ingredients and in Canada at human-grade (and inspected) manufacturing plants, which makes me a little more confident. The food industry here is heavily regulated and meeting human food plant level inspections (voluntarily) is good PR.

  • The pet food recalls have gotten more and more frequent the last couple of years, it’s so scary. Thanks for this info and the tips on food storage to keep pet food safer.
    Love & Biscuits,
    Dogs Luv Us and We Luv Them

    • In part, it’s a good thing because the FDA is keeping a closer eye on things, hence the increase in recalls. It’s bad because what the increased inspections are revealing.

  • I learned about this when studying nutrition – and I think it’s great you’re creating awareness for these molds (and defining aflatoxin and tremorgenic mycotoxins). Great post!

  • Ahh this stuff is so scary! But this is very useful information. Thanks for sharing.

  • Such important information. I’ll be sharing for sure. Thank you! And thanks for joining our Blog Hop today, too!

  • Wow! Very interesting – and in need of sharing. Thank you for this information.

    • With a little bit of preparation and recognition of the signs, if you seek treatment immediately, we an often help your pet recover. The nasty one (aflatoxin) is luckily very rare anymore.

  • Wow this is very informative and useful! Thanks for sharing 🙂

  • Pet food companies can be so dishonest sometimes! It is very troublesome that they get away with putting these types of things in pet foods until enough animals die that the public is outraged. I hope that in the future we will see improvements in the regulation of pet food. There doesn’t necessarily need to be more rules, there just has to be effective rules that are well enforced.

    • The number of vegetable protein derivatives that can artificially bump the protein content in a food is saddening. We see high protein numbers and thing there’s more meat, when in reality it’s coming from a protein undigestable by animals.

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