Assessment of commercial companion animal kefir products for label accuracy of microbial composition and quantity

Kefir is a fermented beverage containing yeast and bacteria produced by the fermentation of water or milk with kefir grains. Lack of regulation for probiotic-containing fermented food sold for companion dogs and cats creates the potential for misreporting on viable microbial counts, taxonomy, and label claims. In this study, the microbiota of six companion animal kefir products were measured quantitatively using standard plating techniques. Microbial composition of these products was also characterized by using high-resolution, long-read amplicon sequencing of the 16S rRNA gene. Five products (83%) listed specific microorganisms, and four products (66%) guaranteed colony forming units (CFU)/g on their label. To enumerate viable lactic acid bacteria (LAB), two lots of each homogenized product were plated upon opening and following 14 d on deMan Rogosa and Sharpe (MRS) agar and incubated under anaerobic and aerobic conditions. Results from point of opening revealed that all commercial kefir products with a guaranteed CFU/g overstated the number of microorganisms present by at least 1 log, with only one product exceeding 1 × 109 CFU/g. Sequencing results demonstrated that none of the labels claiming specific bacterial genera and species on their labels were correct, and all products contained at least three additional bacterial species above the minimum detectable threshold (0.001% relative abundance) that were not disclosed by the manufacturer. In addition to the incorrect viable CFU and bacterial taxonomies, several of the product labels and websites contained a wide range of health claims, none of which are supported by the companion animal literature. Our results demonstrate a low level of accuracy in the labeling of commercial kefir products intended for use in dogs and cats. Regulatory agencies, veterinarians, pet food professionals, and pet owners must scrutinize these products and demand a higher level of accuracy and quality in the future.