Probiotics in veterinary medicine

Intestinal microflora

In all animals, the gastrointestinal (GI) tract is home to several different microorganisms known as the microflora. The number of microorganisms in the GI tract is thought to be around 1012, which is more cells than are found in the rest of the body together. The GI tract is sterile at birth, but is almost immediately colonized by bacteria from the birth canal and the environment. Once the microflora is formed, it is unique to the animal and generally remains stable over time. However, several factors can affect the microflora, e.g. stress, diet, medicine and age.

Barrier of defence

The microflora is very important to the health of the host. The GI tract is the largest immune organ in the body and serves as a barrier of defence against invading pathogens. Roughly 70% of the immune system originates in the digestive tract, and so a balanced microbial ecosystem is crucial for optimal health. Dysbiosis is a term used to describe an imbalance in the microflora, and it is now a general perception that alterations in the microflora play an important role in various GI disorders. Dysbiosis can occur because of such things as antibiotic use, dietary changes (intolerance or indiscretion), gastrointestinal disease, stress or life-stage. Symptoms associated with intestinal dysbiosis include diarrhoea, vomiting, weight loss and changes in appetite.

Presentation of probiotics

The history of live microbial feed supplements dates back thousands of years. As early as 2500 B.C. wall paintings depict the practice of inoculating milk to induce fermentation. The meaning of the word ‘probiotic’ as it is used today was not defined until 1989 by Ray Fuller. He described probiotics as being “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance”.

Probiotics can be used to alter the intestinal microflora to a more favourable balance, thus proving very helpful in cases of intestinal dysbiosis. Probiotics exert their effect in several ways, which can be divided into the following modes of action:

• competition for nutrients and adhesion sites;
• alteration of the microbial metabolism;
• stimulation of the immune system;
• direct antimicrobial effect.

Probiotics in veterinary medicine

The use of probiotics in veterinary medicine is growing. Many veterinarians have seen great results not only when treating gastrointestinal disorders, but also for prophylactic purposes. Probiotics have proven helpful in providing preventative and supportive care for both humans and pets. They are useful in cases of antibiotic-associated diarrhoea and in the prophylactic approach to diarrhoea in dogs and cats housed in animal shelters. 

Other studies have shown positive effects on the immune system, e.g. puppies supplemented with E. faecium SF68 had a better response to the CDV vaccine than non-supplemented did. Similar positive effects on vaccine responses have also been shown in kittens.

A new generation of pet food

Based on the growing awareness of probiotics and their health benefits, a new group of pet foods has emerged – so-called functional foods. Functional foods are defined as “foods that contain some health-promoting components beyond traditional nutrients”. Functional foods are consumed as part of a normal everyday diet and are not classified as supplements. One way to modify foods to become functional is by adding probiotics.

Probiotic pet food should not be considered as a diet meant only for pets with some kind of GI disease, but as a standard food with extra benefits. Thus it can be eaten on a daily basis by all pets. Probiotics contribute to the everyday wellbeing of pets because they help to keep the intestinal system balanced.

When providing nutritional supplements for pets, compliance is important. Many manufacturers are producing pet foods containing probiotics; however, since probiotics are not drugs, there are fewer regulations regarding their use as there are for supplements and food additives. Various studies have reported poor quality control with probiotic products. 

A significant percentage of products either do not contain the organisms or the number of organisms stated on the label, or they contain additional species. Based on several tests and studies, there seems to be a great difference in the quality of probiotic pet foods. More control and regulation is needed for the manufacturing of probiotic products for pets, and especially veterinarians but also pet owners are advised to take available published evidence and experience into account when choosing probiotic diets.