What Are Mycotoxins in Dog Food? What Researchers Found When They Tested 60 Commercial Samples
A 2019 peer-reviewed study published in Toxicology Communications tested dry and wet dog foods from five major US manufacturers. JustFoodForDogs foods had no detectable mycotoxins — with or without grains.
TOXICOLOGY COMMUNICATIONS
SAMPLES ANALYZED FROM FIVE BRANDS
WESTERN UNIVERSITY OF HEALTH SCIENCES
MYCOTOXINS SCREENED
THE RESEARCH
The study at a glance
A 2019 study published in Toxicology Communications investigated commercially available dog foods off retail shelves, sent them to a reference laboratory, and tested them systematically for mycotoxins (toxic compounds produced by certain molds that commonly grow on grains).
The researchers tested 60 commercial dog food samples — both dry and wet varieties, grain-inclusive and grain-free — across multiple brands. All testing was conducted by a certified reference laboratory in Seattle using industry-standard methodology for pet food.
The design was straightforward: a real-world snapshot of products available on store shelves, not a controlled feeding experiment.
PEER-REVIEWED · OPEN ACCESS
Toxicology Communications · 3(1) · pp: 61-66 · August 2019
Comparison of mycotoxin concentrations in grain versus grain-free dry and wet commercial dog foods
Authors:
John H. Tegzes, MA, VMD, Diplomate ABVT; Brian B. Oakley, PhD; Greg Brennan, DVM, PhD
Western University of Health Sciences & University of California, Davis
A total of 60 dog food samples were analyzed for 11 different mycotoxins using stable isotope dilution LC-MS/MS methodology at IEH Laboratories.
KEY FINDINGS
What the study found
These are the researchers’ published conclusions.
9/12
DRY GRAIN FOODS WITH DETECTABLE MYCOTOXINS
Tegzes et al., Toxicol Commun, 2019
Zero
DETECTABLE MYCOTOXINS IN JFFD SAMPLES
Tegzes et al., Toxicol Commun, 2019
Fusarium
ONLY FUNGAL CLASS DETECTED
Tegzes et al., Toxicol Commun, 2019
STUDY DESIGN
What the researchers tested
The study used a standard mycotoxin panel run by an independent reference laboratory. Here’s what that means in plain language.
SAMPLE SET
60 Commercial dog foods
Samples included dry and wet dog foods from five major US manufacturers. Both grain-containing and grain-free formulations were included across each category, allowing direct comparison between food types and formats.
METHOD
INDUSTRY-STANDARD MYCOTOXIN PANEL
Samples were analyzed by an independent reference laboratory in Seattle using industry-standard methodology for pet food mycotoxin testing. The panel screened for eleven specific mycotoxins across multiple fungal classes.
CONTEXT
WHY MYCOTOXIN ARE STUDIED IN PET FOOD
Mycotoxins are secondary metabolites produced by molds that grow on grain crops. They can be present in pet food through contaminated grain-based ingredients. Their presence in commercial pet foods has been documented in research conducted in multiple countries.
MYCOTOXINS SCREENED
The study screened for eleven mycotoxins across two fungal classes. Only Fusarium-derived mycotoxins were detected in any samples — and only in dry grain-containing foods.
Aflatoxin B1
Aflatoxin B2
Aflatoxin G1
Aflatoxin G2
Deoxynivalenol
Fumonisin B1
Fumonisin B2
HT-2 Toxin
Ochratoxin A
T-2 Toxin
Zearalenone
"Results of the study demonstrated measurable mycotoxin concentrations in dry dog foods containing grains but not in grain-free dry dog foods, or in wet foods either containing grains or grain-free. This study suggests that the risk of mycotoxin exposure is higher in dry dog foods containing grains."
COMMON QUESTIONS
Questions pet parents ask about this study and what it means.
What are mycotoxins and why do they matter in dog food?
Mycotoxins are secondary metabolites produced by molds that grow on grain crops. They can carry through into pet food when contaminated grain-based ingredients are used. Because they are heat-stable, standard food processing including high-temperature extrusion does not fully eliminate them. Their presence in commercial pet foods has been documented in research from multiple countries. This study examined how their presence varied by food format (dry vs. wet) and grain status.
Which mycotoxins were found, and in which kinds of food?
Only Fusarium-derived mycotoxins were found in any sample: deoxynivalenol (DON), fumonisin B1, fumonisin B2, and zearalenone. These were detected exclusively in dry dog foods that contained grains — 9 of the 12 dry grain-containing foods tested. No aflatoxins, ochratoxin A, HT-2 toxin, or T-2 toxin were detected above limits in any sample. No wet foods — grain or grain-free — had detectable mycotoxins.
Why do mycotoxins appear more in grain-based dry foods?
Grain crops — corn, wheat, barley, and others — are common substrates for the molds that produce mycotoxins. Dry kibble is typically made from commodity grain ingredients processed at scale. The combination of grain-based ingredients, high-temperature extrusion, and extended shelf life creates conditions where mycotoxin carryover from contaminated grain inputs can persist in the finished product.
What are Fusarium mycotoxins?
Fusarium is a genus of mold commonly found on grain crops globally. The mycotoxins it produces, including deoxynivalenol (DON), fumonisin B1 and B2, and zearalenone, were the only compounds detected in the study. These are among the most commonly studied mycotoxins in the pet food safety literature.
Does grain-free kibble always have lower mycotoxin risk than grain-containing kibble?
In this study, no grain-free dry foods had detectable mycotoxins. The researchers concluded that the risk of mycotoxin exposure is higher in dry dog foods containing grains. However, this is a finding from a single study of 60 samples and should not be interpreted as a universal guarantee. Individual products vary, and the study’s authors note that further research would be valuable.
Why did wet foods (even ones containing grains) have no detectable mycotoxins?
The study does not draw a direct conclusion, but the researchers note that mycotoxins are primarily associated with the grain inputs used in dry pet food manufacturing. Wet and fresh foods typically use different ingredient sources and production methods than dry kibble.
LEARN MORE
Understand the science
Other studies and plain-language guides to the concepts behind this research.
CITATION
Tegzes, J. H., Oakley, B. B., & Brennan, G. (2019). Comparison of mycotoxin concentrations in grain versus grain-free dry and wet commercial dog foods. Toxicology Communications, 3(1), 61–66. https://doi.org/10.1080/24734306.2019.1648636
This page summarizes published scientific research for educational and informational purposes only. It is not intended to diagnose, treat, cure, or prevent any disease or health condition in your dog. Ingredient safety and food quality research is ongoing. Always consult your veterinarian with questions specific to your dog’s health.