Development of a polymerase chain reaction-based method to identify species-specific components in dog food

To determine whether there is a relationship between species-specific mitochondrial DNA (mtDNA), especially canine and feline mtDNA, and detectable amounts of pentobarbital in previously analyzed dog food samples.

31 dog food samples previously analyzed for pentobarbital (limit of detection, 1 microg/kg).

Polymerase chain reaction (PCR) analysis was performed on dog food samples by use of PCR primers specific for either canine, feline, equine, bovine, porcine, ovine, or poultry mtDNA.

PCR amplicons specific for feline or canine mtDNA at a 0.007% (70 microg/g [wt/wt basis]) or 0.0007% (7 microg/g) level, respectively, were not found in the 31 dog food samples. Most of the 31 dog food samples had a PCR amplicon on PCR analysis when a PCR primer set capable of simultaneously detecting mtDNA of cows, pigs, sheep, goats, deer, elk, and horses was used. Results of PCR analysis by use of primers specific for bovine, swine, sheep and goat, or horse mtDNA revealed amplicons specific for bovine or swine mtDNA only in 27 of the 31 samples. Analysis of the remaining 4 samples failed to yield amplicons for any mammalian mtDNA. Pentobarbital was detected in 2 of these 4 samples. Results of PCR analysis correlated with the stated ingredient list for most, but not all samples.

Because canine and feline mtDNA were not found in a set of retail dog food samples, these results indicate that the source of pentobarbital in dog food is something other than proteins from rendered pet remains.