By Kelly S. Swanson, PhD, The Kraft Heinz Company Endowed Professor in Human Nutrition, University of Illinois at Urbana-Champaign, USA
Because dogs are considered to be members of the family by most pet owners today, their health and well-being is a top priority. As with humans, nutritional products supporting gastrointestinal health are some of the most popular. Many pets are healthy, but loose stools, constipation, and various gastrointestinal disorders and diseases such as inflammatory bowel disease and irritable bowel syndrome are common. In fact, within the pet food conversation, digestive health improvements have been the most discussed health benefits among social media discussion posts over the past 2 years (see here). Given the high interest in digestive health, it is not surprising that the canine microbiome has been of great interest over the past decade, with many recent reviews reporting on the overall composition of the gastrointestinal microbiota and how it is impacted by diet (Barko et al., 2018; Alessandri et al., 2020; Wernimont et al., 2020). Gastrointestinal microbiome changes contributing to or resulting from digestive diseases have also been documented in dogs (Redfern et al., 2017; Ziese and Suchodolski, 2021). Animals under high levels of stress or undergoing antibiotic therapy are also known to have poor stool quality and an altered gut microbiota (i.e., dysbiosis) (Pilla et al., 2020).
Dietary fibers and prebiotics are commonly used in complete and balanced diets to improve or maintain stool quality, provide laxation, and positively manipulate the microbiota of healthy animals. The use of probiotics is also popular in dogs, but the route of administration, efficacy, and reason for use is usually different than that of fiber and prebiotics. Probiotics are usually provided in the form of supplements (e.g., powders, capsules, pastes) and are most commonly used to treat animals with gastrointestinal disease rather than support the healthy condition. Live microbes are added to many dry extruded foods as ‘probiotics’, but in many cases, maintaining viability and evidence for a health benefit for dogs is lacking for these products. Such microbes would not meet the minimum criteria to be called a ‘probiotic.’ Viability is a challenge because most HACCP plans for producing complete and balanced pet foods include a kill step that inactivates all microorganisms. Therefore, inclusion must be applied post-extrusion on the outside of the kibble. Even if applied in this way, low numbers of viable organisms are common (Weese and Arroyo, 2003). Post-production inclusion is not possible for other diet formats (e.g., cans, pouches, trays). Although spore-forming bacteria that may survive the extrusion process have been of interest lately, evidence of efficacy is lacking thus far.
Even though health benefits coming from the inclusion of live microorganisms in dog foods is not supported by the peer-reviewed literature, such evidence exists for many probiotic supplements. The clinical effects of probiotics in the prevention or treatment of gastrointestinal diseases in dogs have been reviewed recently (Schmitz and Suchodolski, 2016; Suchodolski and Jergens, 2016; Jensen and Bjornvad, 2018; Schmitz, 2021). Although some similarities exist, recent research has shown that distinct dysbiosis networks exist in dogs compared to humans (Vazquez-Baeza et al., 2016), justifying unique prevention and/or treatment strategies for dogs.
One population of dogs shown to benefit from probiotics has been those with acute idiopathic diarrhea and gastroenteritis, with a shorter time to resolution and reduced percentage of dogs requiring antibiotic administration being reported (Kelley et al., 2009; Herstad et al., 2010; Nixon et al., 2019). Probiotic administration has also been shown to benefit dogs undergoing antibiotic therapy and those engaged in endurance exercise – two conditions that alter the gastrointestinal microbiota and often lead to loose stools. In those studies, consumption of a probiotic helped to minimize gastrointestinal microbiome shifts and reduced the incidence and/or shortened the length of diarrhea (Gagne et al., 2013; Fenimore et al., 2017). Dogs diagnosed with inflammatory bowel disease have also been shown to benefit from probiotic consumption (Rossi et al., 2014; White et al., 2017). In these chronic conditions, drug therapy is almost always required, but probiotics have been shown to help normalize intestinal dysbiosis, increase tight junction protein expression, and reduce clinical and histological scores.
So what is the bottom line? Well, for dogs with a sensitive stomach and/or digestive health issues, probiotics may certainly help. Rather than relying on live microbes present in the dog’s food or adding a couple spoonfuls of yogurt to the food bowl each day, it is recommended that owners work with their veterinarian to identify a probiotic that has the best chance for success. The probiotic selected should provide an effective dose, be designed for dogs, target the specific condition in mind, and be backed by science. As summarized here, it is important to remember that all probiotics are different so the specific microorganism(s), supplement form, storage conditions, and dosage are all important details to consider.
Kelly Swanson joined the ISAPP board of directors in June, 2020, providing valuable expertise in animal gut health and overall health. Swanson also chaired the 2019 ISAPP-led international consensus panel on the definition of synbiotics.
ISAPP board member Prof. Dan Tancredi kindly provided pictures of Simka, pet Samoyed, for the post.