Although binding has shown to be an effective strategy to control certain
mycotoxins, some of them are difficult to bind and hence cause harm to the gut barrier function of animals. Adding glucose biopolymers to contaminated feed can help.
Yvonne van der Horst, technical manager, Selko Feed Additives and Anna-Katharina Oudshoorn, researcher, Nutreco R&D
Despite all efforts to grow and store feed grains of optimal quality, still numerous batches are contaminated with mycotoxins produced by moulds. Feeding these grains to animals may cause serious health problems as well as a decrease in animal performance. It is therefore that products have been developed to reduce or eliminate the effects of these mycotoxins.
Several studies show that purified and activated smectites effectively bind mycotoxins such as Aflatoxins, but their effect on binding Fusarium toxins, such as Deoxynivalenol (DON) and Zearalenone (ZEA), are less established. Some mycotoxins are known to have a negative impact on the gut barrier function. DON triggers an inflammatory response in the intestinal epithelial cells, causing diarrhoea as well as malabsorption and immune modulation. Ochratoxin A (OTA) is identified to cause rapid inflammation, diarrhoea and increased bacterial translocation. Both increase gut wall permeability by the breakdown of tight junction proteins and specifically the removal of specific claudins as well as occludin, allowing bacteria and viruses to easily pass through the intestinal wall and enter the bloodstream.
Stronger tight junctions
A healthy gut and an optimal functioning gut barrier are essential for animal health and performance. Mycotoxins are known to damage the intestinal wall, which may lead to an increased risk of infections and malabsorption of nutrients. Since not all mycotoxins can be neutralised by binding, it is important to include extra protection mechanisms. A special focus should be laid on the mode of action through which mycotoxins exert their negative effects on animal health and performance. Therefore, mycotoxin control should contain multiple protection mechanisms that go beyond binding, including mechanisms which counteract mycotoxin induced tight junction damage.
Recent scientific research confirms that a specific glucose biopolymer may contribute to a healthy status of the gut during exposure to mycotoxins. It enhances the epithelial integrity by protecting tight junction proteins from being damaged or displaced by ingestion of DON or OTA. Dietary supplementation of this glucose biopolymer proved to affect cytokine expression in porcine liver and stimulate the innate immune response in the porcine gastrointestinal system (Ryan et al 2012). Besides that, it alleviated the intestinal mucosal barrier impairment of broiler chickens challenged with Salmonella typhimurium (Shao et al 2013). Other findings show that glucose biopolymers stimulate the toll like receptor 2 (TLR2) and reduce the breakdown of the ZO-1 proteins in the tight junction complex, maintaining the natural intestinal barrier. Subsequently the ZO-1
protein complex moves closer to the cell wall reducing the tight junction permeability. This means stronger tight junctions and a better barrier against bacteria and viruses (Figure 1).
Improved gut health
Based on these findings, Selko Feed Additives and Nutreco R&D together developed TOXO-XL (hereafter called 'biopolymer'), a feed additive which combines multiple protection mechanisms that go beyond binding mycotoxins. Next to a smectite based binder and effective immunity supporting components, the product contains a specific glucose biopolymer that enforces the natural intestinal barrier and reduces mycotoxin induced tight junction damage. In order to prove the efficacy, a series of trials was done in which the effect on animals receiving mycotoxin contaminated feeds was measured. The focus was especially on the ability of the 'biopolymer' to strengthen the gut wall and to reduce absorption of potentially harmful substances.
A first study showed that the 'biopolymer' was successful in maintaining a healthy status during consumption of maximum EU levels of DON, ZEA and OTA contaminated feed by weaned piglets. Adding these mycotoxins to the feed led to an increase in gene expression of the tight junction proteins claudin and occludin (Figure 2).
This indicates increased protein production which is hypothesised to be caused by the removal of these proteins from the tight junctions by DON and OTA. The glucose biopolymers significantly reduced the gene expression, which suggests that they protect the tight junctions from being broken down by the mycotoxins. As an indirect effect, the 'biopolymer' significantly improved fecal consistency which is one of the indicators for intestinal health. A broiler trial gave insight into the positive effects of glucose biopolymers on growth, organ characteristics and blood parameters of broilers during exposure to very high mycotoxin levels. Relative liver weight (RLW) of broilers which were supplied with high mycotoxin contaminated feed (Aflatoxins, Fumonisins, T-2 toxin) was significantly higher compared to animals fed diets without mycotoxins (Figure 3). When the 'biopolymer' was included into the feed with high mycotoxin levels, RLW was significantly decreased.
Effect on Fumonisins
Fumonisins are not easily absorbed by the intestinal wall, however, they can pass through when tight junction quality is reduced. They are potent inhibitors of ceramide synthase, which influences cell structure and signalling. During ceramide synthase, complex sphingolipids are compiled from sphinganine (SA) and sphingosine (SO). Inhibition of this process causes an elevation of sphinganine concentration in the blood, leading to an increase in the SA/SO ratio exposed in animals. This ratio can indicate the Fumonisin level in the blood; the higher the ratio, the more Fumonisins are present. The results from the broiler trial showed that SA/SO ratio is significantly increased by the high mycotoxin level diet, indicating that Fumonisin was taken up by the animal (Figure 3).
The inclusion of the 'biopolymer' in the mycotoxin contaminated diet significantly lowered the SA/SO ratio compared to the mycotoxin group, indicating that addition of the 'biopolymer' to the diet is effective in reducing migration of Fumonisins through the intestinal wall. Usually mycotoxins severely reduce feed intake and body weight gain of animals, but in this study it was shown that a blend of a smectite clay binder, immunity supporting components and a specific glucose biopolymer added to feed with very high mycotoxin concentrations is effective in reducing the negative effects of mycotoxins on the growth and performance of broilers.
This is accomplished by boosting the intestinal barrier, leading to a positive effect on animal's gut health and
References are available on request from the authors
Article featured in AllAboutFeed 22.3 2014