Probiotic use in companion animals: No or go?

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Humans use probiotics successfully for many conditions. A researcher from the United Kingdom evaluated the evidence of probiotic use in dog and cat gastrointestinal diseases. This thorough review article, “Value of probiotics in canine and feline gastroenterology,”¹ also summarizes the legislation surrounding probiotic product use in small animals in the United States and discusses probiotics’ presumed mechanisms of action.

The US government regulates probiotics based on the product’s intended use. The United States Food and Drug Administration (FDA) regulates probiotics as dietary supplements, food ingredients, biologics, or drugs. The USFDA’s Center for Veterinary Medicine regulates animal food products.

This review reports that researchers have performed studies on pet food to determine if the food contained all of the probiotic organisms listed with the correct level of probiotic claimed. The results were dismal and showed that of the 19 foods tested, none of them contained all the probiotics claimed, 11 contained additional related micro-organisms, and some showed no relevant bacterial growth at all.¹

The exact mechanism of action of probiotics in small animals is unclear. Probiotics are thought to displace intestinal pathogens, produce antimicrobial substance, enhance innate and adaptive immune responses, and/or upregulate various nonspecific cellular defense mechanisms.¹

Some trials identified beneficial effects. Small animals with immunosuppressive-responsive diarrhea or idiopathic diarrhea experienced a reduction in clinical severity and a more tolerogenic microenvironment in the intestinal mucosa when taking probiotics that contained S. boulardii or de Simone formulation.¹ Preliminary evidence suggests that there may be some benefits from probiotic administration in small animals that have parvovirus infection. There may also be favorable outcomes when probiotics are used in cats with constipation.¹

Studies that evaluated the use of probiotics in cats and dogs with acute or chronic GI conditions did not always find a beneficial effect. These studies suffered from quite a few limitations. Some clinical trials didn’t have a control group, included animals with diseases that were poorly defined, and applied nonspecific inclusion criteria. Other limitations include allowing animals with infectious diseases in studies that evaluated idiopathic or stress-related diarrhea and inadequate sample sizes with some trials containing only 6 animals.

These studies’ limitations and the discrepancy in measured outcomes make it difficult to compare them. More well-designed studies are clearly needed to evaluate the benefits of probiotic use in small animals that have acute or chronic gastrointestinal diseases so that conclusions may be applied in clinical practice.

Reference

1. Schmitz SS. Value of probiotics in canine and feline gastroenterology. Vet Clin North Am Small Anim Pract. 2021;51(1):171-217. doi:10.1016/j.cvsm.2020.09.011

Bean is a 2022 PharmD Candidate at the University of Connecticut