A new study published in Acta Veterinaria Scandinavica, the official journal of the Veterinary Associations of the Nordic Countries, has found that many pet food brands contain unspecified animal parts that are not listed on labels.

The study, conducted by researchers at the University of Nottingham, examined 17 popular wet pet foods for dogs and cats in the UK. Researchers said they examined the presence and authenticity of animal sources of proteins in pet food in the wake of the 2013 horse meat scandal in the human food chain.

The pet foods were sampled for the relative presence of DNA from bovine, porcine, chicken and horse sources. In the samples, no horse DNA was detected, but there were substantial levels of unspecified animal species in most products tested. The study found that 14 of those brands contained cow, chicken and pig DNA, but none of those animals were listed on the label. Of the seven brands with prominent descriptions containing the term “with beef,” only two were found to contain more bovine DNA than porcine and chicken DNA combined.

 Researchers concluded that there is a need for the pet food industry to be more transparent with consumers in the disclosure of the types of animal proteins in their products. They said full disclosure will allow consumers to make more informed choices on purchases that are particularly important for pets with food allergies, reduce the risk of product misinterpretation, and avoid potential religious concerns.