Microbes are everywhere! Your horse is literally covered externally and inundated internally with microorganisms. When these microbes are termed ‘probiotics,’ they sound less intimidating. Regardless of your perception of microbes, probiotics appear to be poised for enhanced widespread use in a variety of species, including horses.
The term probiotic generally refers to ‘good’ microorganisms that offer a beneficial effect on the host. Pathogens are the ‘bad’ microorganisms that elicit a cascade of events leading to a disease condition. Likewise, probiotics can be referred to as direct-fed microbials (DFMs), and these terms are used interchangeably.
Most of us associate ‘probiotics’ with beneficial bacteria like the Lactobacillus acidophilus found in yogurt; however, yeast (fungi) can function as probiotics as well. At least nine genera of bacteria are currently approved for use as DFMs for animals, including Aspergillus, Bacillus, Bifidobacterium, Lactobacillus, and Enterococcus. The primary genus of yeast approved for use as a probiotic is Saccharomyces. Interestingly, not only the species, but more importantly the strain of bacteria, can have a significant impact on the host. For instance, Aspergillus oryzae is a common bacterium that produces enzymes that enhance digestive function, but Aspergillus fumigatus can cause severe, bloody diarrhea in mammals.
INTENDED USES OF PROBIOTICS
Probiotics are classified by the Food and Drug Administration (FDA) and AAFCO as GRAS – Generally Recognized as Safe. This simply means that experts have evaluated the bacteria or yeast, and determined them to be safe for their intended use, primarily to:
- enhance digestive function or efficiency
- competitively exclude pathogens
- stimulate immune function
- modulate changes in digestion and microflora population due to stress, changes in weather or feeding regimen, administration of antibiotics or de-wormers
Enhance Digestive Function
Some equine probiotic supplements feature a combination of yeast, bacteria and supplemental digestive enzymes. Their unique combination has been shown to enhance digestive efficiency, especially when it comes to protein and certain minerals; however, this is probably not the primary justification to feed a probiotic, as the next several reasons are considerably more compelling.
Competitively Exclude Pathogens
Several lines of evidence exist for probiotics to competitively exclude pathogens. Basically, the beneficial bacteria and the pathogenic bacteria compete for the same food and binding sites in the gut. If we increase the number of beneficial bacteria relative to pathogenic bacteria through feeding a probiotic, we lessen the likelihood and potential severity of gastrointestinal upset and disease due to pathogens. This result has been replicated numerous times in meat animal species and companion animals.
Stimulate Immune Function
The intestinal tract is the largest organ in the body directly involved with immunity, and approximately 70% of immune function is generated from the gut. Thus, probiotics and the inherent natural microflora of the gastrointestinal tract play a vital role in maintaining health and preventing disease. More specifically, Saccharomyces cerevisiae spp. boulardii, a specific strain of yeast, has been shown in a variety of species to stabilize the natural microflora during periods of stress and dietary transition.
Modulate Changes in Digestion and Microflora
Stress, changes in weather or feeding programs, administration of antibiotics or certain de-wormers can affect the microflora population of the gut. Certain bacteria thrive on fibrous feedstuffs (forages) at a more neutral gut pH, while some bacteria flourish on starches (grains) at a more acidic gut pH. Changes in feeds or feeding programs ultimately change the population, species and diversity of the microbial population of the gut, especially the hindgut. One mode of action proposed for the beneficial effects of equine probiotics is that of modulating dietary transitions – essentially smoothing out the peaks and valleys so the effects are less drastic.
Does this same evidence hold true for preventing colic? It would be a stretch to conclude that it does, but there really isn’t any published evidence that supports or contravenes effectiveness of probiotics against bouts of colic.
WHEN TO FEED PROBIOTICS
Horses who are stressed from showing, travel, changes in weather, dietary transitions, vaccinations, de-worming or having recently been on a course of antibiotics potentially will benefit from a daily feeding of a high potency, multi-strain probiotic. Ideally, begin supplementation about 10-14 days before the onset of known stressors and continue for 10-14 days after the period of stress. This paradigm is especially beneficial when transitioning a horse from hay to pasture (spring) or pasture to hay (fall).
Several probiotic pastes are available that provide flexible, positive dosing for use when traveling, between feedings and prior to known stressful events. The same rules apply to pastes and powders when evaluating probiotics for horses.
As with any supplement, the proof is in the concentration or strength of the active ingredients. The concentration of probiotic bacteria and yeast is measured in Colony Forming Units (CFUs). A CFU is a measure of viable bacteria or fungi per unit of dry weight (CFU/g) or liquid volume (CFU/ml). When selecting an equine probiotic for a specific intended use, be cognizant of these criteria:
1. Bacteria versus yeast: Generally, probiotic bacteria are more expensive to produce than yeast, so a company can reach higher CFU more inexpensively by using yeast instead of bacteria. Feeding predominantly yeast may not be the most desirable approach. Note: yeast and yeast culture are not the same! Yeast is viable with a measurable CFU; whereas yeast culture has no guarantee of living cells – only the metabolites from fermentation.
2. Species diversity: When reading a label guarantee, look for a variety of bacterial strains, yeast, and supplemental digestive enzymes to ensure that you have a robust equine probiotic.
3. Minimum daily dose of 40 billion CFU: Daily feeding of a probiotic with a minimum of 40-50 billion CFU is required for success using any oral probiotic product for horses.
4. Value = price per billion CFU: What is the cost per 50 billion CFU as a single daily dose?
5. Reputable manufacturer: Purchase equine probiotics from a manufacturer you trust!
Keith A. Bryan, PhD, is Director of Technical Services at Kauffman’s Animal Health, Inc., Lebanon, PA, manufacturers of Kauffman’s Premium Equine and FORTITUDE Equine supplements which feature a variety of DFMs and novel GRAS ingredients for enhancing the health and well-being of horses. He can be reached at firstname.lastname@example.org.