It is not uncommon for residents of the country of Georgia, in the former Soviet Union, to live well more than 100 years.
Many believe that the soil in that province, and a special mix of herbs and plants commonly eaten there, combine to keep these
centenarians going strong. This concept of "you are what you eat" has been popular for many years and has led to a generalized
increase in interest in nutrition.
Horses with chronic disease maintain a persistent level of stress. This is an older horse with Cushing's Disease. Digestion
in older horses is often less than optimal and an improved bacterial microflora may benefit these animals. The possible immune
system stimulation found with probiotics may also be beneficial as these horses attempt to deal with their illnesses.
One area of nutrition that is gaining attention is probiotics. Commonly defined as a live microbial feed supplement that aids
the host animal by exerting health benefits beyond its inherent nutritional value, probiotics have been around for nearly
a century. Much like the favorable plants and herbs of Georgia, early researchers reported that the practice of consuming
fermented milk products by some nationalities resulted in a disproportionate longevity among those ethnic groups.
It was felt that these fermented milk products or early versions of probiotics, enhanced the normal or beneficial balance
of intestinal microflora and, through some unknown influences, helped people live better and longer.
The very name probiotic was proposed to counterbalance the term antibiotic. The concept of "good" and "bad" bacteria was developed
with antibiotics being used to destroy "bad" bacteria and probiotics being eaten to maintain "good" bacteria.
As society has become more conscious of overall fitness- both of the exterior body and of interior systems, and more accepting
of natural, herbal and dietary therapies, the issue of probiotics has come to the forefront.
Many probiotic products have been marketed recently for both humans and horses. Some equine probiotics are sold as separate
additives and some probiotics are added into processed foodstuffs.
These products come with a wide array of claims for use and efficacy and horse owners are being told that probiotics can help
treat everything from diarrhea and respiratory problems to EPM and poor performance.
While there may well be beneficial uses for these products, it is unlikely that the overzealous marketing directors are completely
correct. Equine practitioners must be able to sort through the fact and the fiction regarding these products in order to make
helpful and medically sound recommendations to clients concerning probiotic use.
Dr. J. Scott Weese, DVM, presented a paper on probiotics at the 2001 American Association of Equine Practitioners convention
in San Diego. Weese provided a review of the current knowledge regarding probiotics and stated, "Probiotics are specific tools,
not 'cure-alls'." While he feels that probiotics have a role in the treatment of various conditions in horses, he also points
out that there is a need for much more research in this area.
Stall rest is difficult for horses. Post-surgical cases and medical cases where horses must remain stall-bound place stresses
on the metabolic and physiologic systems of the horse. Probiotic use in these cases may be helpful and could constitute a
significant part of the nutritional component of rehabilitation.
Mechanism of action
One area of probiotic research is the search for a mechanism of action. Part of the definition of probiotic is that these
products provide benefits beyond simple nutrient value. Exactly how these probiotics work and how they produce their results
is not currently known. This lack of step-by-step knowledge on a physiological level has led to skepticism on the part of
scientists and has opened the door for all types of marketing claims and promotions.
Weese feels that this lack of knowledge about exactly how probiotics work is understandable since he points out that there
is still much that is unknown about the workings of the intestinal tract and the normal composition of intestinal microflora.
It has been postulated that probiotics work by competitive inhibition of enteric or intestinal pathogens. The good bacteria
essentially outgrow the bad bacteria.
Other possible mechanisms of action include the production of antimicrobial substances by beneficial bacteria, the simple
competition for nutrients which hopefully depletes the "bad" bacteria, competition for receptor sites in the intestinal lining,
a generalized immune stimulatory effect and an ability of probiotics to decrease the absorption of pathogenic antigens. There
are studies that seem to support any number of these possible theories of probiotic action but to date, no definitive proof
that explains all probiotic action and effects has been found.
Another problem in evaluating and recommending probiotic use is the issue of deciding exactly which bacteria are really the
Most probiotic products contain types of lactic acid bacteria. But Weese points out that not just any lactobacillus will do.
Only certain strains of specific bacteria have positive health benefits. Additionally, similar related strains may actually
be harmful and lead to disease rather than a benefit healer.
It is important that the companies producing these probiotics pay careful attention to their composition and that veterinarians
and horse owners be aware of the consequences of the use of inferior products.
"Quality control is a concern," writes Weese and he adds "misidentification of probiotic bacteria is common in commercial
preparations." Drs. Hamilton-Miller, Shah and Smith reported in the British Medical Journal that only two of 13 probiotics
offered for sale in England matched their label claims to their actual composition. Much like the current situation for glucosamine
and chondrotin feed supplements, probiotics are considered nutraceuticals and the Food and Drug Administration only requires
minimal levels of control as to content and purity. The potential for mislabeling and poor quality control is very real.
The issue of dose is also important in that too small a number of even the correct microorganisms are likely to have little
positive effect. It is estimated (based on extrapolation from human data) that the daily dose of microorganisms needed to
colonize the average horse's digestive tract is between 10 to 100 billion colony forming units (CFU).
Weese adds, "this dosage may be difficult to achieve with some commercial probiotic preparations."
There is some good research, mostly in humans, that does show that probiotics can have therapeutic effects.
Improvements have been made in the treatment of many forms of diarrhea through the use of various probiotics and it is hoped
that similar effects may be seen in horses. Currently it is difficult to wholeheartedly recommend these products because of
a number of factors.