Used with permission from Today's Breeder, Nestlé Purina PetCare Company.
The role of the intestinal tract in nutrient absorption is well recognized. However, it is the microflora that naturally inhabit the intestinal tract and their vital role in maintaining normal functioning of the gut and immune system that are often overlooked.
Animals that do not establish a healthy microflora balance tend to have a weak immune system and fail to thrive, says Gail Czarnecki-Maulden, Ph.D., Purina Senior Research Nutritionist. "All animals are born with a sterile gut. It is the mother that passes on healthy microflora that are essential for life when she licks her puppies to clean them. The microflora balance an animal establishes early in life pretty much stays with it."
The intestinal tract is often the "first line of defense" for the body and must be in good order for an animal to maintain a healthy immune response. Gut microflora are divided into three broad categories: potentially harmful, beneficial and those with apparently neutral or unknown effects.
"Beneficial microflora include the lactic acid bacteria lactobacilli, hifidobacteria and enterococcus," Czamecki-Maulden says. "These microflora produce short-chain fatty acids that help to modulate the gut pH and provide a source of fuel for the cells lining the gut. Most nutrients are absorbed better at a lower pH. This in turn strengthens the intestinal cells and helps enhance nutrient absorption. Microflora also produce digestive enzymes and help to synthesize vitamins."
One of the most important roles of lactic acid bacteria is to stimulate the immune response in the gut, Czarnecki-Maulden says. These microflora can directly block attachment of potential pathogens to the intestinal wall. They also are known to modulate the intestinal environment to inhibit the growth of potential pathogens and produce immune-stimulating factors.
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 an 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, Czarnecki-Maulden says. "These probiotics are typically lactic acid bacteria such as enterococcus faeciurn, lactobacillus and bifidohacteria. 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."
Other benefits of probiotics include an increase in secretory IgA, a protective immune factor, and an increase in phagocytosis, or destruction of invading pathogens. In addition, some probiotics have antiinflammatory properties in humans, Czarnecki-Maulden says.
To determine the effect of probiotic supplementation on immune function in healthy dogs, Czarnecki-Maulden led a study in which Beagle, Labrador Retriever, Fox Terrier and Manchester Terrier puppies were fed either a control diet or the same diet supplemented with the probiotic Enrerococcusfaeceurn (SF68). Diets were fed from weaning to 1 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 1 year of age in puppies fed the probiotic-supplemented diet," she says. "In addition, secretory IgA levels were significantly higher in the puppies fed SF68. This prolonged vaccination response and increase in secretory IgA indicate that ingestion of the probiotic SF68 primes the puppy's immune system to better handle external challenges."