Tag Archives: bacteria

  • Prebiotics in Horses

    Written By Dr. Kris Hiney

    Last month we discussed the use of probiotics in horses, including the definition and types of probiotics, their effectiveness, and when their use might be warranted.  This month we will address a closely related and often misunderstood topic: prebiotics.  The use of both of these feed additives may work synergistically to promote digestion in your horse, keep his immune system in top shape and allow him to face the various stressors which may be present in his life.

    As opposed to probiotics, prebiotics are not live organisms.  Rather, they are chains of specific types of carbohydrates which promote the growth of organisms which are beneficial to the well-being of the host.  Prebiotics are derived from a variety of products, including milk, fruit, vegetables and fermentation byproducts.  These are typically short chains of fructo-oligosaccharides (FOS), which are a mix of fructose and glucose, mannose oligo-saccharides (MOS) or galacto-oligosaccharides (GOS).  Simply stated, oligosaccharides are shorter chains of carbohydrates or saccharides (sugars) as compared to polysaccharides such as starch, glycogen of cellulose.  For a review of carbohydrate terminology, please see: Equine Carbohydrate Disorders Part 1. Because of the type of bonds joining the carbohydrates together, prebiotics are not able to be enzymatically digested in the stomach and small intestine.  Instead they provide substrates for fermentation of a specific group of bacteria and thus allow them to flourish.  It may be helpful to think about prebiotics as providing food for the good types of bacteria, rather than feeding your horse.   In ruminant animals such as cattle, sheep and goats, they have a direct effect on the rumen microflora, while in monogastrics and hind gut fermenters such as the horse, prebiotics pass to the hindgut where they exert part of their beneficial effect.   Horses also have a substantial microbial population in the foregut as well.  While the use of prebiotics in gastric health of the horse has not been explored, it does appear promising as a potential tool in maintaining stomach health.

    So why would you have to feed the bacteria?  Certainly a horse on a high forage diet would have adequate nutrient delivery to those microbes, correct?  Well, different types of organisms utilize different substrates for food.  If there is more food available for one type, they will be more successful and reproduce at a higher rate.  Cellulytic bacteria are responsible for fermentation of the fibrous portion of a horse’s feed and are typically associated with a higher pH in the gut.   However, amylotic bacteria prefer substrates such as sugars and starches. When we over feed concentrate to our horse or forages containing more rapidly fermentable sugars, these amylotic bacteria flourish and can produce negative by products for the horse.  Prebiotics typically provide substrate for more beneficial strains of bacteria including bifidobacteria (found more in humans), lactobacillus and lactate utilizing bacteria.  The use of prebiotics has shown to be effective in preventing the rapid and detrimental shift in bacterial population which occurs when horses are overfed concentrates. Now certainly it would never be advisable to subject our horses to a rapid increase in carbohydrates.  However, we could think of supplementation of prebiotics during periods of dietary adaptation, shifting to a new feed source or when starting to graze in the spring as a potential way to modulate gut microflora. However, supplementation of prebiotics would not be an alternative to slow controlled adaptation to new diets.

    Prebiotics may have more benefits than just helping to increase fermentation or stabilize the population of the hindgut.  While not digested in the small intestine, prebiotics help prevent the colonization of pathogenic bacteria such as Salmonella and E coli.  Doing so improves the overall health status of the animal.  They do so by binding to the carbohydrate receptor sites on the bacteria which are used to bind to intestinal epithelial cells. By “tricking” bacteria into binding to these oligosaccharides, they are prevented from binding to epithelial cells and proliferating. Promoting the growth of the beneficial bacteria may even limit the growth of pathogenic bacteria.  Bifidocacteria and lactobacillus possess their own bactericidal/anti-microbial effects against harmful bacteria. The “good” type of bacteria may also release enzymes which destroy the toxins produced by pathogenic bacteria.  Clearly it is easy to see why the feeding of prebiotics has gained much attention in feeding production species as an alternative to antibiotics.

    In addition to these direct effects on bacteria, immune-stimulatory effects of prebiotics have been observed in a variety of subjects. These appear to be not only in response to viral or bacterial challenge, but even with allergen stimulated immune responses. Human infants supplemented with prebiotics which mimic those found in breast milk developed fewer infections compared to those not receiving prebiotics.  There is also some evidence that intestinal epithelial cells may be able to transport prebiotic oligosaccharides, putting them in direct contact with cells of the immune system.  In an in vitro equine study, peripheral blood mononuclear cells (lymphocytes, macrophages) showed an increased immune response when these cells were cultured in the presence of GOS and FOS. When these same cells were challenged with LPS, the effect was even more pronounced in cells cultured with FOS and GOS.  The use of prebiotics may be a tool in helping to develop the immune system of neonatal foals, as has been proposed in other species.    Finally, prebiotics may serve as natural anti-oxidants themselves. In part this could help explain their immunomodulatory effects as well.  Therefore, consider using prebiotics when the animal might be undergoing periods of stress, as stress typically weakens the immune system.

    Even beyond their ability to affect the population of micro-organisms in the hindgut or stimulate the immune system, prebiotics may also help with insulin sensitivity.  This has been shown in dogs, veal calves, rodents and humans.   The effect is believed to be due to the alteration of fermentation in the hindgut, resulting in a shift in the ratio of volatile fatty acids which are produced. In obese horses supplemented with short chain FOS, a modest improvement in insulin sensitivity was observed after 6 weeks.  Prebiotics may serve as an aid to restoring insulin sensitivity, but certainly should not replace diet modifications or a sound weight loss program.

    Certainly the addition of prebiotics to the human food supply is increasing, and a number of products designed for use in pet foods and production animals point to the value of this natural foodstuff in promoting the health for all. There do not appear to be any risks associated with feeding prebiotics, and the number of proven health benefits is quite expansive.  The evidence for their effectiveness in improving the health and well-being is so many species of animals is substantial.  So if your horse needs help with digestion, stress, his immune system or even insulin resistance, consider a prebiotic.

  • Digestive Aids in Horses

    Written By Dr. Kris Hiney

    This month we will explore the use of digestive aids in horses, in particular probiotic usage. Probiotics are increasingly used in human medicine, production animal species, and of course in horses.  More owners are looking for safe and effective alternatives to pharmacological methods for promoting the well-being of their horses.   In this article we will discuss what type of organisms fall under the probiotic umbrella, the form in which they may be fed, their effectiveness and when their use might be warranted.

    In general, probiotics are live organisms which are fed with the intention of their survival within the gastrointestinal tract.  The original concept behind the use of probiotics was to provide a beneficial type of microorganism which can alter the fermentation process in the hindgut, or to shift the microbial population away from more negative types of organisms.  Typically these organisms promote digestion and alter the types of volatile fatty acids that are produced.  This was typically referred to as a competitive exclusion effect.  However, it is becoming more widely understand that probiotics may have farther reaching effects than just simply outnumbering undesirable bacteria.  This differs from when organisms are fed for their nutritive value, such as often done with yeasts.

    Horse owners have many options when selecting probiotics, including powders, pills, pastes, feeds, live culture yogurt or even innoculations of fecal microflora from healthy horses.  The key feature for a probiotic to be effective is that it is able to survive exposure to acid, bile and enzymes in the foregut of the horse and reach the hindgut alive.   In addition it must remain viable during processing and storage of the product. Further, microorganisms must be present in sufficient quantities to have an effect.   From extrapolations in human studies, it is suggested that foals be provided with a minimum of 10 to 20 billion colony forming units or CFUs with some studies suggesting an increase of 10 fold in adults.  Therefore concentrated forms of probiotics are often the most effective, rather than just a feed with added probiotics which may contain insufficient organisms.  It is highly recommended that horse owners read product labels carefully in choosing a digestive aid for their horse to ensure the product contains living organisms at sufficient numbers.  Unfortunately many commercial products may not actually even contain the amount of microorganisms listed on the label.  In a study from 2002, products contained as little as 2% of the CFUs claimed on the label.    In addition, some claims may be misleading and actually only contain fermentation products, which are not live cultures and therefore not probiotics.

    Beyond viability and amount of probiotics, the type of organism contained in the probiotic is key.  The most common classes of probiotics are the lactate utilizing bacteria including lactobacilli, bifidobacteria and enterococci. These bacteria are those that convert lactate to propionate in the gut which may help stabilize colonic pH.   Live yeast cultures have also been used, in particular Saccharomyces cervisiae.  This differs from the use of yeast products which may be fed in order to supply vitamins or protein from the process of digestion of the yeast itself.  When looking for a yeast supplement intended to be a probiotic, be sure that it actually contains live yeast   Most species of organisms in probiotics are not typically found inhabiting the gut of the horse. Thus they fail to form permanent stable colonies in the gut, and will no longer be present after administration has been ceased.  Therefore continual supplementation may be necessary depending on the desired outcome.

    Live yeast and bacteria supplementation may have beneficial effects beyond that of just supplying a different microorganism with fermentative capabilities.  Some yeasts may release enzymes which digest the toxic by-products of pathogenic bacteria.  It is also believed that yeasts and lactate using bacteria may have immunostimulatory effects, stimulating the gut associated lymphoid tissue.  This enhances the immune system of the horse and may make them more capable of handling exposure to pathogens. Other pathogenic bacteria such as Salmonella and E coli may bind to the yeasts rather than the epithelial tissue of the gut, thus preventing their colonization. Supplementation of live yeast has also been shown to improve digestibility of fiber and increase the amount of lactobacillus in the hind gut which again may be protective against acidotic conditions in the hindgut.

    Probiotics are frequently administered when there is believed to be a disruption in normal gut microflora, such as during bouts of diarrhea, following anti-biotic administration or other gastric upsets.  This can include any stressful period for the horse such as travel, new environments, or alteration in diets. Horses supplemented with yeast and subjected to transport had greater biological diversity of bacterial species in the hindgut, and an increase concentration of lactate using bacteria and cellulytic bacteria.  Thus these horses maintained a healthier hindgut population compared to non-supplemented controls.  Supplementation of live boulardii yeast, a sub species of Saccharomyces cervisiae resulted in a shortened period of diarrhea and a quicker return to normal feces in horses suffering from enterocolitis compared to a placebo group.  Horses in this study had a broad range of causative factors for the diarrhea.  Thus probiotic administration may be an additional therapeutic tool in managing colitis or diarrhea in horses.    Probiotics may also reduce the detrimental effects of a high starch diet on the microbial population.  Typically high starch diets promote the growth of amylotic bacteria and decrease the population of cellulytic bacteria, thus suppressing fiber fermentation.  In addition, the by-products of amylotic bacteria are responsible for lowering the pH of the hind gut.  If probiotics are used in conjunction with higher concentrate diets, the overall health of the gut may be improved.

    So when is a probiotic right for you?  Certainly during periods of digestive upsets, probiotics can help return the microbiology of the gut of the horse to a healthier state.  They may also assist a horse during times of stress, not only preserving the health of the GI tract, but also the health of the horse itself.  Probiotics promote a stable pH in the gut and can assist in fermentation in the gut.  There a very few negative indicators for probiotic usage, rather just be sure that you choose an effective product.

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