In previous studies, some dog foods were found to contain measurable levels of pentobarbital. Since this agent is used to euthanize animals, speculation arose that dog food contained rendered pet remains. This study was done to determine whether the dog foods previously analyzed to contain pentobarbital contained species-specific mitochondrial DNA (mDNA). The authors used polymerase chain reaction to identify mDNA from canine, feline, equine, bovine, porcine, ovine, and avian sources. The minimum detection level was 0.0007% (wt/wt basis), which translates to 7 kg of rendered protein in 1000 metric tons of dog food. Protein from horses, dogs, and cats was not found in any of the 31 foods tested. The only common feature of all samples containing pentobarbital was the presence of animal fat.

The polymerase chain reaction testing method could also be used to assure the validity of label claims. One food tested that listed poultry meal and lamb meal on its label had no detectable ovine mDNA. Another sample with 2 different poultry ingredients listed was negative for avian mDNA. The discrepancy could be a result of experimental error or product mislabeling. Another 7 samples that did not list poultry ingredients did test positive for avian mDNA. These products did list animal digest or animal fat as an ingredient, so this may have been the source of the avian proteins.

COMMENTARY: A risk assessment conducted by the Food and Drug Administration determined that the low levels of exposure to sodium pentobarbital (pentobarbital) that dogs might receive through food is unlikely to cause adverse health effects. Results of this assessment and of the original testing of foods for pentobarbital can be found at

Development of a polymerase chain reaction-based method to identify species-specific components in dog food. Myers MJ, Farrell DE, Heller DN, Yancy HF. AM J VET RES 65:99-103, 2004.