Probiotics to Boost Immune System
G.L. Czarnecki-Maulden and J. Benyacoub Nestle Purina PetCare Research, St Joseph, MO
The role of the intestinal tract in nutrient absorption is well recognized. However, the microflora that naturally inhabit the intestinal tract and their vital role in maintaining normal functioning of the gut and immune system are often overlooked. The intestinal tract is often the ‘first line of defense’ for the body and must be in good order for the animal to maintain a healthy immune response. Gut microflora can be divided into three broad categories: (1) potentially harmful, (2) beneficial and (3) those with apparently neutral or unknown effects. Beneficial microflora include the lactic acid bacteria (e.g., lactobacilli, bifidobacteria and enterococcus). These microflora produce short chain fatty acids that modulate the gut pH and provide a source of fuel for the cells lining the gut. This, in turn, strengthens the intestinal cells and helps enhance nutrient absorption. Microflora also produce digestive enzymes and synthesize vitamins. One of the most important roles of lactic acid bacteria is to stimulate the immune response in the gut. These microflora can directly block attachment of potential pathogens to the intestinal wall. They are also known to modulate the intestinal environment to inhibit the growth of potential pathogens and produce immune stimulating factors. Animals born into a sterile environment where they do not establish a healthy microflora balance have a weak immune system and fail to thrive.
Stress, travel, aging, changes in environment and long-term antibiotic therapy can upset the normal balance of microflora in the intestinal tract. Probiotics, live beneficial microflora ingested by the animal, can help restore and maintain microflora during these times of stress. Probiotic supplementation is often recommended in puppies being raised on milk replacer to help establish a healthy microflora balance. These probiotics are typically lactic acid bacteria such as enterococcus faecium, lactobacillus, and bifidobacteria. . Most of the research to date has been conducted with mice, humans and livestock. In these studies, probiotics have been proven to prime the mucosal immune system to be able to respond quickly and efficiently to challenges. Secretory IgA, a protective immune factor, increases in response to ingestion of some probiotics. Additionally, phagocytosis, direct destruction of invading pathogens, increases in response to ingestion of several different probiotic strains. Some probiotics also have anti-inflammatory properties and are effective in the treatment of inflammatory bowel disease and colitis in humans. For example: Probiotics have been proven to decrease illness in children attending daycare and to decrease incidence of diarrhea and viral shedding. Likewise, traveler’s diarrhea and antibiotic-associated diarrhea are effectively prevented and treated with probiotics. When probiotics are consumed pre-natally, children have a lower incidence of atopic dermatitis and anti-allergenic benefits of probiotics have been demonstrated in numerous studies. As a result, the use of probiotics in human medicine, particularly in the area of pediatric medicine, is increasing.
While numerous studies have been published on immune benefits of probiotics in other species, little research has been published with pets. There are a number of potential explanations for the lack of information. Screening probiotics for potential use in pet foods is a laborious process and includes proof of safety, investigation of potential benefits in vitro, proof of survival of the strain in the intestinal tract and proof of efficacy. Probiotics are not stable under normal environmental conditions and need to be specially protected to ensure survival throughout the shelf life of the product. To determine the effect of probiotic supplementation on immune function in healthy dogs, Beagle, Labrador Retriever, Fox Terrier and Manchester Terrier puppies were fed either a control diet or the same diet supplemented with the probiotic Enterococcus faeceum (SF68). Diets were fed from weaning to one year of age. Specific canine distemper virus antibodies were measured before and at timed intervals after vaccination. While antibody titers started to decrease in puppies fed the control diet, they remained at post-vaccination levels through one year of age in puppies fed the probiotic-supplemented diet. In addition, secretory IgA levels were significantly higher in puppies fed SF68. This prolonged vaccination response and increase in secretory IgA indicates that ingestion of the probiotic SF68 primes the puppy’s immune system to better handle external challenges.
Gail L. Czarnecki-Maulden received her BS in Animal Science from Cornell University and her MS and PhD in Animal Nutrition from the University of Illinois. In 1984, she became an Assistant Professor of companion animal nutrition in the Department of Animal Sciences at the University of Illinois and was promoted to Associate Professor 1989. In 1990, Gail joined Nestle Purina Petcare Research where she is currently a senior research nutritionist. She is a member of the University of Illinois Division of Nutritional Sciences External Advisory Panel. Gail was a member of the AAFCO Canine and Feline Nutrition Experts Subcommittees, which set nutrient standards for dog and cat foods in the US. Gail has published over 60 articles and abstracts in the area of pet nutrition.
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