Several brands of pet food contain unspecified animal species, and various proportions of beef, chicken and pork that are not explicitly identified on the product labels, according to research in the open access journal Acta Veterinaria Scandinavica.
Researchers from the University of Nottingham determined the relative presence of DNA from cow, chicken, pig and horse in 17 leading dog and cat wet foods, readily available in UK supermarkets. They then compared their results with the animal species details that were disclosed on the pet food labels.
While no horse DNA was detected, a major finding was the relative abundance of proteins from unspecified animal species in 14 of the 17 products.
Amongst these 14 samples, cow, pig and chicken DNA were found in various proportions and combinations but were not explicitly identified on the product labels.
Seven products with prominent descriptions containing the term "with beef" comprised between 14% and 56% cow DNA. Only two of the seven were found to contain more cow DNA (>50%) than pig and chicken DNA combined. With the remaining five samples, three contained more pig than cow DNA.
Another six headline labels that highlighted "chicken" or "with chicken" contained 1% to 100% chicken DNA of which two products contained more pig or cow than chicken DNA.
Whilst the present practice in pet food labelling is within current regulatory guidelines, the findings highlighted weaknesses in product labelling that could adversely affect pets and their owner expectation.
Lead author Kin-Chow Chang from the University of Nottingham said: "It may be a surprise to shoppers to discover that prominently described contents such as 'beef' on a tin could, within the guidelines, be a minor ingredient, have no bovine skeletal muscle (meat) and contain a majority of unidentified animal proteins.
"There is a need for the pet food industry to show greater transparency to customers in the disclosure of the types of animal proteins in their products. Full disclosure of animal contents will allow more informed choices to be made on purchases which are particularly important for pets with food allergies, reduce the risk of product misinterpretation by shoppers, and avoid potential religious concerns."
The study is limited by the relative amount of DNA detected for each host species calculated as a percentage of total detected DNA. This means that the figures do not represent the species DNA content as a percentage of the entire product. This is because DNA from species other than cow, horse, pig and chicken would not have been recognised.