It is claimed that by the addition of fibre to a diet, there is a beneficial effect by maintaining intestinal barrier function and preventing bacterial translocation even in the absence of oral nutrients (Spaeth et al 1990). Some soluble dietary fibre even though fermentable remains only partially fermentable (Fibersol-2©), and has been reported to also produce beneficial intestinal morphological changes. All fibre is not equal however, with citrus pectin failing to providing benefits. However kaolin and cellulose fibre does provide benefit. The effect of fibre are seen with changes to intestinal morphology, mucosal mass, and gut bacterial ecology. Fibres having a high viscosity significantly slow stomach emptying. To maintain high rates of stomach emptying it is important that soluble dietary fibre does not affect the viscosity of the electrolyte solution. Fortunately there are complex carbohydrates that meet this objective. Soluble dietary fibres such as resistant maltodextrins (e.g. Fibersol-2©, and Nutriose© FB06 and FM06) do not adversely affect viscosity and maintain stomach emptying.
Response of Lactobacillus strains to Prebiotics (e.g. resistant maltodextrins)
Some information is available from studies comparing prebiotic’s effects on Short Chain Fatty Acids (SCFAs), but not on the species of bacteria that are responsible for the changes (Flickinger et al 2000).
There is also data suggesting that some of the prebiotics included as resistant maltodextrins and betacyclodextrin have some limited effect on the degree of Lactobacillus fermentation in vitro (Hartemink 1999). However these reports are incomplete in several respects, and do not include L reuteri in the studies reported.
Studies show Non-Digestible Carbohydrates (NDOs) can show an increase of Lactobacilli numbers in spite of having no effect in in vitro studies. Typical of these is with resistant starch (amylomaize) which leads to an elevation of lactobacilli that could not have been anticipated since no lactobacilli utilized amylomaize starch in vitro. This suggests that other bacteria fermenting the amylomaize are degraded to some extent by other bacteria which may supply some limiting factor to lactobacilli numbers. (Conway et al 2001, q Brown et al 1998)
Conclusion: In vivo studies are required to show any prebiotic benefit. Contrary to this faecal numbers are not recommended to be reliable indicators of lactobacilli responses. Lactobacilli numbers may be prone to show the effects of stress, and reductions of numbers are reported to be lower in animals under stress (review Tannock 1983).
The role of the large intestine
Studies have shown that 60% of a standard electrolyte volume is excreted from failure of absorption (Naylor q. Guards & Tennant, 1986). The earlier separation of absorption between the small intestine and large intestine was shown to be false (Powell, q Nafatalin 1990) with fluid in a normal large intestine absorbed through the activity of butyrate driven sodium absorption ‘with colonic crypts being the final arbiter of stool fluidity’
It has been proposed that non-digestible carbohydrates are the origins of butyrate, being fermented by saccharolytic bacteria present in the large intestine. Not all complex carbohydrates deliver the same proportions of n-butyrate (see Ramakrishna el al 2000).
- resistant amylase starches (Ramakrishna et al 2000). The addition of resistant starch produced a significantly (p = 0.001) reduced period of diarrhoea compared with standard ORT for cholera. This was based on fermentable starch being reduced by 50% in transit through the large intestine, or the equivalent of 25g starch fermented per 2 litre dose of an isotonic electrolyte (327 mMol/L.).
- Resistant maltodextrins (e.g. Fibersol-2® – present in Enervade® and Kryptade®) See prebiotic carbohydrates below. Soluble dietary fibres differ in their effect on the recovery of damaged villus structure.
- It is also possible that undigested simple monosaccharides and disaccharides (lactose) overflowing undigested from the small intestine will also be fermented and potentially provide similar n-butyrate benefits.
The different carbohydrates (e.g. lactose versus starches) delivered to the large intestine ferment producing different ratios of SCFAs (short chain fatty acids), and therefore differ in n-butyrate production.
The colon is the site of significant sodium and water absorption normally which is dependant on energy from n-butyrate specifically. This is potentially an important target for enhanced fluid and electrolyte absorption in dehydrated calves.
The large intestinal cells are dependant on Short Chain Fatty Acids (SCFAs) derived from the bacterial fermentation either from the overflow of undigested carbohydrates (e.g lactose) or non-digestible but fermentable more complex carbohydrates (prebiotic carbohydrates, pectins and rice etc). This enables the normal fluid absorption to also occur from the large intestine, and the generation of higher levels of vitamins (mainly B vitamins) from bacterial fermentation. The bacterial population of the large intestine associated with diarrhoea washout frequently is significantly lower with luminal bacteria significantly more severely affected than mucosal populations. Repopulating the ecological balance can be achieved with certain (stomach-acid resistant) probiotic strains, (Allen et al 2003). Probiotics act in concert with the immune system to provide a wide spectrum of activity. Prebiotics such as fructooligosaccharides act through the promotion of the natural gut flora’s beneficial bacteria (Oli et al 1998). The presence of carbohydrates with specific stereotypic bonding induces multiplication of different populations of saccharolytic bacteria in the large bowel, and this occurs in the recovering animal with diarrhoea (Oli et al 1998).
Probiotics and recovery from rotavirus & cryptosporidiosis
Allen et al 2003 has reviewed published papers on probiotics and human infant diarrhoeas. They examine aetiology and probiotic strains used. All results have been subject to review before being admitted for analysis. Their conclusion is that some probiotics do provide a useful adjunct to some diarrhoeas, with certain provisos also reported.
A report by Casas & Dobrogosz (2000) examines and report on one probiotic strain Lactobacillus reuteri . This strain is also included in the report by Timmerman et al.(2002) with benefits to calf general health following a mix of probiotic strains.
The conclusions from these reports is summarized
- Strain specificity to the host species may be important to obtain clinical benefits.
- Some strains are only suitable as live organisms and therefore subject to issues of storage.
- Acid resistance of these strains to enable passage to the intestine is important. Some human strains marketed for their probiotic benefits fail to pass effectively in sufficient numbers to provide any benefit (UK data- Consumer)
- Some strains of organisms researched and developed exhibit a range of effects that differ between strains. L reuteri for example has some antibacterial factors (reuterin).
- Some may provide a dominant and exert an exclusivity which decreases the pro-inflammatory effects of other natural flora strains (Christiansen et al, 2002).
- Health benefits occur outside the immediate gut environment (Timmerman et al, 2005).
Seaweed and fibres
Nutritional components included in some electrolytes include seaweeds. They are a source of natural dietary fibre. Alginates found in seaweed also stimulate mucus cells to release mucin. Other dietary fibres such as pectin, or gum Arabic do not have this direct effect (Plaisancie 2006). This benefit is therefore different from that achieved by bacterial fermentation and the production of butyrate for cellular energy. Seaweeds are also high in certain aminoacids which are also important constituents of mucin (e.g. threonine), and they also potentially aid palatability (pers. comm.)