Mannan oligosaccharide-based nutritional supplements

Mannan-oligosaccharide based nutritional supplements, MOS are widely used in nutrition as a natural additive. MOS has been shown to improve gastrointestinal health as well as overall health, thus improving wellbeing, energy levels and performance. Most MOS products, particularly those that have been scientifically reviewed, derive from the cell wall of the yeast, Saccharomyces cerevisiae.

History of MOS as a nutritional supplement
The initial interest in using MOS to protect gastrointestinal health originated from work done in the late 1980s. At this time researchers looked at the ability of mannose, the pure version of the complex sugar in MOS, to inhibit salmonella infections. Different studies showed that salmonella can bind via type-1-fimbriae (finger-like projections) to mannose. The binding to mannose reduces the risk of pathogen colonization in the intestinal tract. Different forms of mannose-type sugars interact differently with type-1-fimbriae. The form present in the cell wall of Saccharomyces cerevisiae (α-1,3 and α-1,6 branched mannans; for more details see Structure defines function) is particularly effective at binding pathogens. Based on those facts, Newman et al. investigated the effect of MOS in calves and reported improved performance.

The gut is home to billions of microorganisms. Nutrition must not only provide the necessary nutrients, it must also support a balanced microflora. In recent years consumers and the media have placed an ever greater emphasis on wellness, energy levels and overall well being. MOS as a natural nutritional supplement offers a novel approach to support the microflora and thus improve overall health and well-being.

Experiments with rats have indicated that D-mannoheptulose injections created an aversion to carbohydrates. Glucomannan supplementation reputedly promotes weight loss in overweight persons as a result of fiber-filling and reduced fat uptake. But although a high fat diet supplemented with mannan oligosaccharide in mice reduced food intake, there was no significant effect on body weight, total fat, or visceral fat.

In farmed animals, gut health has an additional dimension, as a healthy gut enables more efficient use of feed, called the feed conversion ratio. Over many decades antibiotic drugs have been added to the diet of farmed animals at non-therapeutic levels in the absence of disease, in order to enhance the feed conversion ratio, accelerate growth and protect the animal's health, therefore increasing profitability for producers. Today, however, there is a global push to reduce the use of medically important antibiotics as feed additives for farm animals, due to concerns about this practice promoting the emergence of antibiotic resistant micro-organisms. This trend has fueled interest in natural nutritional concepts. Based on a large body of research MOS has established itself as a one of the more important natural additives in farm animal production. The effect of MOS on animal performance was analysed in several meta-analyses (statistical analyses of final reports from trials that essentially contain the same experimental treatments) for poultry,   pigs,  and calves. These analyses reported improvements in performance with MOS.

Effects of MOS on the intestinal microflora
As mentioned earlier MOS affects bacterial attachment in the intestinal tract. In controlled studies with chickens, a reduction in the prevalence and concentration of different strains of salmonella, as well as E. coli, was reported. Reductions in E. coli were also reported by several other researchers. Salmonella is a zoonoses, therefore an efficient control system, which includes dietary measures is critical in order to produce safe food. Further research has shown a reduction in clostridia, another common intestinal pathogen. The effects of MOS at controlling E. coli and salmonella are quite consistent. However, reported effects on promoting beneficial bacteria, such as lactobacilli and bifidobacteria are more variable. The application of molecular techniques allows us to study the composition of the intestinal microflora, giving us a more detailed picture of the complex changes following MOS supplementation.

Effects of MOS on intestinal structure and function
A large surface area is key for optimal digestive function, therefore the surface of the small intestine should be covered with long healthy villi. Yang et al. reported better energy digestion when including MOS in broilers. Several studies with MOS in poultry have looked at the intestinal structure and discovered longer villi and a more shallow crypt. Comparable changes in intestinal structure have also been reported in fish. In rainbow trout, supplementing the diet with 0.2% level of MOS resulted in an increase in gut surface area, microvilli length and density, and altered microbial populations.

A shallow crypt is a good indicator for an efficient small intestine, which requires fewer nutrients for renewal. With a low renewal rate the intestinal cells become more mature, allowing for more efficient digestive enzyme production and nutrient absorption. Research has shown increased production of enzymes such as; maltase, leucine aminopeptidase, and alkaline phosphatase with MOS.

To protect the villi and intestinal surface, the gut produces protecting mucus. This mucus is produced in specific cells called goblet cells. In general the number of goblet cells is an indicator of mucus production. Researchers found that goblet cell numbers were increased with MOS. The importance of those changes for animal health is still being debated by scientists.

MOS as a nutritional supplement for companion animals
MOS is included in diets for horses, dogs, cats, rabbits and birds by feed manufacturers, mainly due to its benefits for their health. MOS as a nutritional supplement offers a natural approach to support the microflora and thus improve overall health, well-being and longevity.

MOS for dogs
Rapid changes in the microflora and/or the proliferation of intestinal pathogens can lead to gastrointestinal diseases. Therefore, a number of trials have been carried out to explore the efficacy of MOS in improving gut health in dogs.

To reduce the risk of digestive upsets it is critical to keep the concentrations of potential pathogens low. MOS has been shown to reduce faecal E. coli and C. perfringens and tended to have greater concentrations of lactobacilli and bifidobacteria. Older dogs tend to have reduced concentrations of bifidobacteria. A significant increase in bifidobacteria concentration was noted with MOS supplementation to diets of senior dogs, thus counteracting the negative effect of age on colonic health.

The mechanism of action for reducing the numbers of C. perfringens may differ from that previously explained for bacteria with type-1-fimbriae. Research in other species has demonstrated that MOS has an effect on intestinal morphology as well as both innate and acquired immune system components, which may help to explain the observed reductions in C. perfringens. Research shows an increase in serum lymphocytes and lower plasma neutrophils when adult dogs were supplemented with MOS and FOS. These findings indicate an improvement in immunity that, in turn, gives rise to increased protection against intestinal pathogens.

Other areas of interest to dog owners are the effect of MOS on nutrient digestibility and stool quality; both for health and practical (poop-a-scoop) reasons.

MOS as a nutritional supplement for farm animals
Mannan oligosaccharides have been widely evaluated in feeding trials. As animal health and performance are influenced by many factors other than nutrition, the responses to a feed additive will vary between production systems. Therefore, a concept such as MOS should not be evaluated based on single trials. A meta-analyses, which summarizes a large number of published research trials allows for a more comprehensive overview.

MOS for poultry
The first study testing MOS in poultry showing an improvement in performance was peer-reviewed published in 2001. It showed an improvement in feed conversion, indicating that birds are converting feed more efficiently into body tissue. An efficient feed conversion ratio (FCR) is important for the overall efficiency and thus is a key contributing factor to sustainable poultry production. In addition, it is of great economic importance to the producer. Over the years, a series of papers looking at performance effects under different production conditions were published. Hooge summarized 44 comparisons in a meta-analyses where MOS was fed between 0.5 to 2 kg / tonne of feed. He concluded that on average MOS led to 1.6% improvements in body weight, 2.0% improvement in FCR and lower bird mortality. Prof. Dr. Gordon Rosen, in his review of 82 comparisons, reported similar effects. After broilers (meat-producing chicken), turkey is the second most important source of poultry meat globally. In turkeys 76 comparisons have shown similar responses to MOS as in broilers. Several studies also suggest that MOS, when added to poultry diets, allows the birds to perform at a similar level as when fed a diet supplemented with antibiotic growth promoters (AGPs).

MOS for pigs
Part of a successful start into a piglet's life is the consumption of sufficient colostrum (milk from the sow the first day after birth). Colostrum contains high levels of immunoglobulins, which protect the piglet from harmful diseases in the first weeks of its life. Several studies have looked at supplementing sow diets with MOS with the aim of improving the health of the sows. A healthy sow produces good quality colostrum and spreads less harmful bacteria in the environment where she gives birth and raises the piglets. Several researchers have reported a significant increase in colostrum production and colostrum quality with MOS. Those changes in colostrum quality and quantity likely explain a reduced pre-weaning mortality and a higher litter size and litter weight at weaning and can thereby help to better protect the piglet from disease, thus improving piglet survival. A recent review of published literature showed that the mortality of young piglets was reduced when MOS was supplemented in the diets of the sow. Keeping the mortality of young piglets to a minimum is important from an economical as well as from an animal welfare point of view.

The next critical phase in a piglet’s life is the time of weaning, when it is separated from the sow. The change from milk to solid feed leads to changes in the intestinal microflora and structure and thus presents a higher risk of intestinal problems. Two meta-analyses involving a total of 123 comparison, concluded that performance was better in piglets fed MOS-supplemented feed. The data also indicated that piglets, which were particularly challenged during this transition phase (showing a slower growth rate due to the challenge), responded particularly well to MOS supplements. Positive performance effects with MOS were also reported in later production phases, however, those effects appear to be smaller than in the very young animals.

MOS for calves
The first trial ever reported with MOS was with young bull calves. Newman et al. noted improved intake and subsequently better growth rates. The health status of young calves is one of the most important factors contributing to growth and performance. Diarrhoea in young calves is a major issue in the dairy sector. The cause can be viral or bacterial, however, E.coli is often involved. As MOS can bind E. coli (see Effects of MOS on the intestinal microflora), it can modify and help to improve the composition of the intestinal microflora. This resulted in a reduction in faecal E. coli counts and improvements in faecal score in calves fed MOS. These improvements were coupled with an increase in concentrate (dry feed) intake and better performance. In addition to the changes in the gut, several authors also noticed improvements in respiratory health, which can also contribute to better performance. Conversely, one trial reported no effects on liveweight gain despite increased feed intake. Higher liveweight gain, similar to that gained with the use of antibiotics, has been achieved following supplementation of milk replacer with MOS.

Dairy cows fed MOS had better immune protection against rotavirus and were able to pass some of this protection on to their calves. The transfer of immunity from the cow to the calves is critical in order to protect the calf from many different diseases.

MOS for aquaculture
Farmed Fish larvae are often fed with live feed cultures. As the intensive nature of live feed cultures provide ideal conditions for the growth of opportunistic pathogens, MOS incorporation into live feeds has been studied to assess the impact on the microbial load, particularly with regards to Vibrio species levels. MOS showed a reduction in Vibrio levels of live feed cultures. These reductions were likely due to the agglutination or binding of Vibrio cells to MOS mediated by the presence of mannose receptors. MOS supplementation has also been shown to reduce the overall cultivable intestinal microbial load and to enhance species richness.

Several researchers have reported improved performance and feed efficiency with MOS in aqua culture. As in terrestrial animals, changes have been associated with effects on the gut and the immune system. Dimitroglou et al. observed alterations of circulating leukocytes proportions as well as increased total leucocyte levels when feeding gilthead sea bream. Torrecillas et al. assessed the dietary inclusion of various levels of MOS on the immune status and disease resistance of sea bass. MOS reduced Vibrio alginolyticus, Vibrio anguillarum and Listonella anguillarum, two important pathogens in aqua fish.

Structure defines function
In the yeast cell wall, mannan oligosaccharides are present in complex molecules that are linked to the protein moiety. There are two main locations of mannan oligosaccharides in the surface area of Saccharomyces cerevisiae cell wall. They can be attached to the cell wall proteins as part of –O and –N glycosyl groups and also constitute elements of large α-D-mannanose polysaccharides (α-D-Mannans), which are built of α-(1,2)- and α-(1,3)- D-mannose branches (from 1 to 5 rings long), which are attached to long α-(1,6)-D-mannose chains. This specific combination of various functionalities involves mannan oligosacharides-protein conjugates and highly hydrophilic and structurally variable 'brush-like' mannan oligosaccharides structures that can fit to various receptors of animal digestive tracts, and to the receptors on the surface of bacterial membranes, impacts these molecules bioactivity. Mannan oligosacharides-protein conjugates are involved in interactions with the animal's immune system and as result enhance immune system activity. They also play a role in animal antioxidant and antimutagenic defense.