Texas Equine Veterinary Association

www.teva-online.org • Page 6 The equine large intestine is a complex and diverse ecosystem, home to billions of microbes. The diversity of this population allows successful fermentation of a variety of feedstuffs and is vital to animal health. Intestinal microbes protect against disease by competitively inhibiting pathogenic bacteria, positively modifying the ecosystem, and playing a role in local inflammatory and immune response. Any disruption of these microflora and their environment can lead to disease. The stability and diversity of these microbial populations are largely influenced by diet. Increasing the ratio of concentrate to forage can increase the amount of starch reaching the cecum and quickly impact the environment. Starch overload in horses occurs when starch intake exceeds two to four grams of starch per kilogram body weight per meal (Potter et al., 1992). Epidemiological studies suggest a link between nutritional management and risk of colic and laminitis. Risk increases with high grain diets, abrupt changes in diet, high starch diets, increased fructan content of pastures, and low quality forage (high acid detergent fiber [ADF] and lignin content). Often the link between nutritional management and risk of disease can be decreased with improved digestion. Inclusion of digestive aids such as prebiotic and probiotic preparations have been suggested as a dietary supplement to improve digestibility of equine diets. Digestive aids are categorized as prebiotics and probiotics with the use of both products simultaneously referred to as symbiotic preparations. These products can be added to commercial diet, or top dressed on an existing ration. Probiotic PreParations Probiotics are defined as living microorganisms which upon ingestion in certain numbers exert health benefits beyond inherent basic nutrition. These products are often referred to as direct-fed microbials composed of bacteria, fungi, or yeast. Probiotics are classified by the FDA as generally recognized as safe (GRAS). The goal of these products is to introduce beneficial organisms to the gastrointestinal system. Successful probiotic preparations provide adequate numbers of viable organisms to the gastrointestinal tract. This can be particularly challenging considering the gastrointestinal arrangement of the horse. Ideally an equine probiotic should be safe and readily survive commercial processing and remain viable during storage. Successful probiotic development is species specific and requires knowledge of the native inhabitants of normal microflora. Therefore, probiotics developed for use in multiple species of animals may not be as effective. The optimal dose of probiotics has not been determined for the horse, and current use relies heavily on effective doses used in humans. Currently, probiotics available for equine use include several types of lactic acid bacteria including Lactobacillus, Bifidobacterium, and Enterococci. Other sources include fungi such as Aspergillus and yeast such as Saccharomyces. Prebiotic PreParations Prebiotics are defined as non-digestible feed ingredients that beneficially effect the host by selectively stimulating growth or activity of bacterial species already present. These products largely support beneficial intestinal microbes by providing substrate that can be rapidly metabolized into volatile fatty acids. In turn, a more favorable environment is created for existing microorganisms, limiting pathogenic organisms. Ideally prebiotics are unable to be enzymatically digested in the small intestine, selectively enrich the environment for specific bacterial and positively alter microbial populations and their activity. The use of prebiotics does not require viable microorganisms and the quality of these products is not influenced by processing methods or storage. Commonly used prebiotics include fructo-oligosaccharide (FOS) or mannan- oligosaccharide (MOS) products. effectiveness of Prebiotics and Probiotics Research regarding efficacy of probiotics and prebiotics in horses is limited and variable in results. Even fewer studies have evaluated PROBIOTIC AND PREBIOTIC USE IN HORSES JOSIE COVERdaLE, dVM Texas a&M Univeristy Veterinary Medical Teaching Hospital

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