Probiotics & Prebiotics

Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School

Introduction
In previous articles I have talked a lot about the importance of gut health in horses. Your horse’s gut plays such an important role in maintaining health and wellbeing. The gastrointestinal tract works hard to digest feedstuffs, make essential nutrients that the horse can’t produce on its own, protecting your horse from disease and even shaping the behaviour of your horse. Thus, it is vital to maintain gut health and to ensure you are managing your horse in a way that promotes gut health through an understanding of the anatomy and physiology of the equine gastrointestinal tract.

Maintaining gut health in horses requires ensuring that enough forage is provided as horses are designed to eat large quantities of fibre on an almost continual basis and therefore feeding forage is important to satisfy your horse’s behavioral needs. If supplementary feeding is required then it is advisable to begin with highly digestive fibre sources, such as alfalfa and sugar beet pulp, and/or by adding oil to the feed. If feeds containing starch are fed, for example mixes containing oats, barley or maize, then these should be fed little and often to avoid overloading the capacity of the small intestine to digest starch.

If changes are made to the diet, they should be done gradually over a period of one to two weeks and this also includes changes to the amount of turnout provided; for example, a stabled horse fed hay moving to 24 hours access to pasture is a sudden change of diet. Other management changes can also impact on gut health, and we know that stress from moving a horse to a different yard can upset the gut microbes as well as travelling and being fed antibiotics. It is also known that having an anaesthetic can impact on the microbial populations in your horse’s gut. A significant element of your horse’s immune system is also located in their gut, which is essential for immune stability and the health of the animal. Therefore, any disruption in the gut can affect your horse’s immunity.

Supporting gut health
In addition to the above measures to help support your horse’s gut health, feeding a gastrointestinal supplement can also be beneficial. Probiotics and prebiotics are extensively used in equine feeding practices to modulate the balance and activities of the gastrointestinal microflora. Prebiotics are described as additives that support microbial growth and one example of this is fructo-oligosaccharides that are not digested by the animal but are fermented by the microbes present in the gut.

Probiotics are defined as “live microorganisms which when administered in adequate amounts confer a health benefit on the host”. After antibiotics were banned in the European Union in 2006, alternative substances producing similar effects, such as probiotics and prebiotics, were developed. Probiotics that are used in animal feeds include bacteria and yeasts; however, whilst probiotics containing bacteria have been used in other species and in research trials in horses, there are none currently registered for use in horses in the European Union (EU). There are three yeast strains approved by the EU under the category of zootechnical additives and as part of a functional group of ‘digestibility enhancers’ for use in horses. Yeasts are single-celled micro-organisms that are part of the fungi kingdom. All of the yeasts that are registered are all strains of Saccharomyces cerevisiae. There is a wealth of scientific evidence that Saccharomyces cerevisiae (S. cerevisiae) has positive effects on health and wellbeing, digestion, gut health, and the performance and behaviour of horses, as well as helping to counter some effects stress and enhance the immune system.

Transvite Excel
Transvite Excel is a supplement that contains a probiotic and prebiotic and is designed to help maintain your horse’s gut health and digestion. Transvite Excel contains the probiotic yeast (S. cerevisiae) and also the prebiotic fructo-oligosaccharides, both of which have been reported to have wide ranging benefits in horses.

In terms of digestion, yeast has been shown to have an important role in the microbial fermentation process in the hindgut of the horse. Yeast is a source of nutrients such as nucleotides, vitamins, organic acids, which are essential for bacterial growth. When incorporated into horse diets, the most common observation in yeast-related research studies is an increase in the fibre-digesting bacteria population and consequently fibre digestibility, mainly in fibre-rich diets. It is also thought that yeast uses oxygen from the gut environment making it more favourable for proliferation and activity of fibre degrading microbes that are known to require an anaerobic environment (no oxygen). Higher levels of fibrolytic bacteria make it more difficult for the less oxygen-sensitive lactic acid-producing bacteria to compete, thus lower levels of lactic acid are produced, and pH is maintained at higher levels, which is beneficial to gut health.

In previously articles, I have also talked about the impact that change can have on maintaining gut health in horses. Studies have shown that yeast can help maintain a healthy hindgut when horses diets are changed by minimising the disruption to the microbial populations in the hindgut. In fact, work at the University of Glasgow has shown that even a change from grass pasture to feeding hay can impact on the microbial populations in the hindgut of horses and when yeast is supplemented the impact of this change is reduced. Yeast can also help maintain a healthy gut when diets containing starch are fed and can also minimise any disruption to the hindgut that can occur as a result of stress; for example, travelling horses, which has been reported to impact on gut microbes. Therefore, feeding yeast when travelling and competing can help minimise disruption to your horse’s gut that can arise from the stress associated with this.

Another aspect of yeast supplementation that has been observed is increased feed intake, which can be of benefit to horses that need to gain weight but have reduced appetite. Research has shown yeast supplementation to promote growth in foals and to improve milk quantity and quality in mares. Yeast is also considered to be a quality protein source for foals. In terms of behaviour, you may recall from my previous articles that there is a growing body of research that has identified a strong link between gut microbiota and an individual’s health and wellbeing, including their behaviour. Consequently, some studies in horses have observed a reduction in stress and aberrant behaviour in horses supplemented with yeast.

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