A collection of technical documents for customers wishing to understand more of the science behind our products.
Written by: Dr Tom Shurlock for and on behalf of GWF Nutrition Limited.
Copyright GWF Nutrition Limited October 2018 - Not for reproduction.
A prebiotic is defined as food ingredients that induce the growth or activity of beneficial microorganisms. As such they need to fulfil certain criteria:
non-digestible and resistant to breakdown by stomach acid and enzymes in the human gastrointestinal tract
selectively fermented by intestinal microorganisms
selectively target and stimulate the growth and activity of beneficial bacteria.
The EC Commission have further defined prebiotics by declaring them to separate from dietary fibre. Dietary fibre can, in the definition above, have a prebiotic effect but are not prebiotics. An obvious example of this is beet pulp. Beet pulp, in several species including horses, has been shown to increase hindgut fermentation of fibre, presumably by encouraging hemicellulytic bacteria (Murray et al., 2006,2008).
Prebiotics, then, are regarded as being factions of dietary fibre that exist outside the fibre matrix. This being said it means that there exists unspecific prebiotic effect from different fibre materials. In the case of a herbivorous animal, such as the horse, the type of fibre fed – grass, beet pulp, alfalfa, oat fibre – have the potential to modify the populations of bacteria and have an impact on the “health” of the gut environment.
Defined prebiotics are mainly oligosaccharides – relatively short chain lengths (in the hundreds, rather than thousands) - of sugars joined by the beta linkage. As such they are not broken down by animal enzymes and can only be degraded by some microbes. Commercially they are mainly of one sugar type and predominantly FOS, GOS, MOS and β-glucans.
This stands for fructo-oligosaccharide and is based on fructose units. Included are scFOS (3-6 units), inulin (long chain) and oligofructose. In dogs they have been demonstrated as encouraging the growth of lactobacilli and bifidobacter which help exclude certain pathogens ((Swanson et al, 2002, Propst. et al, 2003, Zentek et al, 2003), as well as generating high proportions of butyric acid that is beneficial for hindgut cells and also indirectly activate macrophages in the Peyers Patch of the small intestine. Both these mechanisms help downregulate inflammatory processes and so can be regarded as beneficial. However, the main use in dogs is to improve stool characteristics, where its function as a soluble dietary fibre helps bulk and optimise moisture content of faecal material.
In horses, although there is similar effects on microbial populations, because of the apparent lack of bifidobacter in the horse’s gut, there are different effects in the hindgut. Work in yearlings showed a general increase in VFA production, a concomitant rise in lactic acid and a reduction in hindgut pH (Berg et al., 2005). This can be attributed to a rise in lactobacilli but data from a separate trial (Respondek et al., 2008) suggests that there is also a rise in lactic acid utilising bacteria so feeding high levels of barley do not increase normal levels. However, as FOS are used to induce laminitis in trial animals, its use as a prebiotic in horses may be inadvisable. It has been shown to have positive effects in improving insulin sensitivity in EMS horses (McGowan et al., 2013) under restrictive conditions so it may have a specialist role in horses.
Galacto oligosaccharides; based on the sugar galactose, derived from milk lactose, appear to be particularly suitable for fermentation by Bifidobacterium bifidum and are often fed in conjunction with this microbe as a prebiotic (Ogue Bon et al., 2010). In dogs, GOS was seen to alter hindgut microbial populations, increasing bifidobacter species and reducing lactobacilli species, compared to other prebiotics, resulting in higher out put of lactic acid and VFA compared to controls. In piglets, against negative controls, there was a rise in both bifidobacter and lactobacilli, with a concomittant reduction in E. coli and clostridia. Importantly there was evidence of increased small intestine absorptive area – villus height and surface area, - and stimulation of the mucosal immune system (Alizadeh et al., 2016). As a result of the altered hindgut microflora, absorption of minerals have been noted (Weavwe et al., 2011, Bongers, 2003).
In respect to the immune function of prebiotics, GOS supplementation lead to decreased markers for pro-inflammatory cytokines, such as interferon-ϒ and Il-6 (Cornelis Vendrig et al., 2014), whilst there was evidence of pro-inflammatory effects in lipopolysaccharide induced inflammation in horses (Cornelis Vendrig et al., 2013). Both TNF-α and IL-10 were increased, although there was reduction when a FOS/GOS combination was used. The regulation of inflammatory cytokines is a complex system, involving both pro-inflammatory and anti-inflammatory factors, some components being both, but stimulating inflammatory processes, when a pro-inflammatory agent is present is beneficial for rapid repair mechanisms.
Mannan oligosaccharides; based on the sugar mannose they are reported to be moderately fermentable, but mainly by lactic acid producing bacteria (Bolduan, 1999). As such it can be argued that they are not suitable for horses as lactic acid is a known trigger for laminitis. Trials (Gurbuz et al., 2010) showed no advantage of using MOS in horses, in terms of nutrient digestibility, hindgut pH and fermentation characteristics. Immune status was also unaffected. MOS are also reported to be immunostimulants, and resist pathogenic colonization by acting as receptor analogues for Type-1 fimbriae present on E. coli and Salmonella species (Swanson and Fahey, 2002 ). In dogs they have ben shown to act as immunomodulators without affecting nutrient digestibility or hindgut fermentation parameters (Pawar et al., 2017).
These can be described as gluco oligosaccharides and consist of short chains of β-linked glucose chains. Glucans have been extensively reviewed previously (Beta glucans – what do they do? Knowledge base August 2016); in summary they have similar impact on microbial populations as the other oligosaccharides – increases in lactobacilli and bifidobacter – and also a well researched impact on the immune system and inflammatory processes.
Prebiotics, therefore, have two distinct modes of action. By altering the microbial populations they can affect the physiology of the hindgut, and its contents. Prebiotics have been used to improve stool quality in dog feeds and reduce putrefactive compounds such as phenols and indoles (Middelbos et al., 2007); changes in VFA profiles (the ratio between acetate, butyrate and propionate, the VFA,) can help maintain “tight junctions” and gut cell vitality, and so moderate the absorption of negative factors, such as endotoxins and fermentative end products like amines and nitrites. As the result of their action is similar to supplying probiotics, provision of both may be complementary.
In addition, they have the ability to interact with the lymph receptors in the intestine (GALT, MALT) and so activate macrophages and initiate some inflammation processes. As inflammation is the first step in “ring fencing” metabolic or physiological disorders – anything from microbial invasion to allergy to insect bites to obesity – they have an important role in supporting the body’s natural defence mechanisms, especially as they also display anti-inflammatory characteristics, when this is needed.
Choice of the source of prebiotics is another question. For species like dogs, the parameters would be the effect on faecal quality and helping to maintain the immune system; for horses, by contrast, potential effect on immune function is more relevant. Increasing lactic acid bacteria in the hindgut is contradictive to the function of the large intestine, it being the site of fibre fermentation, and a less acidic environment is needed.
Because of this GWF Nutrition use a range of prebiotics, as well as a yeast probiotic from Saccharomyces cerevisiae, both singly (ImmuneAid, XLam), as multiple prebiotics (ConditionAid) or as a prebiotic/probiotic package (Equilibra, Camelibra, Hembra & Cria). By adopting this approach the various benefits of each product can be built into a for-purpose product.
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Berg EL, Fu CJ, Porter JH, Kerley MS. Fructooligosaccharide supplementation in the yearling horse: Effects on fecal pH, microbial content, and volatile fatty acid concentrations
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Bolduan, G. 1999. Feeding weaner pigs without infeed antibiotics. In: Biotechnology in the Feed
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Bongers A, van den Heuvel EGHM. Prebiotics and the bioavailability of minerals and trace elements. Food Rev Int. 2003;19:397–422.
Cornelis Vendrig J, Coffeng LE, Fink-Gremmels J. In vitro evaluation of defined oligosaccharide
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Cornelis Vendrig J, Coffeng LE, Fink-Gremmels J. Effects of orally administered alactooligosaccharides
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McGowan CM, Dugdale AH, Pinchbeck GKL, Argo CM. Dietary restriction in combination with a nutraceutical supplement for the management of equine metabolic syndrome in horses. The Veterinary Journal 196 (2013) 153–159
Middelbos IS, Fastinger ND, Fahey, Jr JC. Evaluation of fermentable oligosaccharides in diets fed to dogs in comparison to fiber standards. J ANIM SCI 2007, 85:3033-3044
Murray et.al. “In vitro fermentation of different ratios of high-temperature dried lucerne and sugar beet pulp incubated with an equine faecal inoculum.” 2006. Animal Feed Science and Technology 129: 89-98.
Murray JMD, Longland A, Hastie PM, Moore-Colyer M, Dunnett C. The nutritive value of sugar beet pulp-substituted lucerne for equids. Animal Feed Science and Technology. 140 (2008) 110–124
Ogue-Bon E, Khoo C, McCartney A, Gibson GR, Rastall RA. Invitro effects of synbiotic fermentation on the canine faecal microbiota. FEMS Microbiol Ecol 73 (2010) 587–600
Pawar ME, Pattanaik AK, Sinha DK, Goswami TK, Sharma K. Effect of dietary mannanoligosaccharide supplementation on nutrient digestibility, hindgut fermentation, immune response and antioxidant indices in dogs. Journal of Animal Science and Technology, Vol 59, Iss 1, Pp 1-7 (2017)
Propst EL, Fickinger EA, Bauer LL, Merchen NR, Fahey GC. A diose response experiment evaluating the effects of oligofructose and inulin on nutrient digestibility, stool quality and faecal protein catabolites in healthy adult dogs. 2003. J. An. Sci 81. 3057-3066.
Respondek F, Goachet AG, Julliand V. Effects of dietary short-chain fructooligosaccharides on the intestinal microflora of horses subjected to a sudden change in diet. J. Anim. Sci. 2008. 86:316–323
Swanson, K. S.; Fahey, G. C . Prebiotics in companion animal nutrition. 2002. , Nutritional biotechnology in the feed and food industries. Proceedings of Alltech's 18th Annual Symposium: from niche markets to mainstream, Lexington, Kentucky, USA, pp 461-473
Weaver CM, Martin BR, Nakatsu CH, Armstrong AP, Clavijo A, McCabe LD, McCabe GP, Duignan S, Schoterman MH, van den Heuvel EG. Galactooligosaccharides improve mineral absorption and bone properties in growing rats through gut fermentation. J Agric Food Chem. 2011;59:6501–10.
Zentek J, Marquart B, Pietrzak T, Ballevre O, Rochat F. Dietary effects on Bifidobacter and Clostridium perfringens in the canine digestive tract. 2003. J. An. Physiol. An. Nutr. 87. 397-407.
Probiotics and Prebiotics: Part 2