ISSUE FOCUS FEED & ADDITIVE MAGAZINE April 2023 29 Thus, endotoxins are a natural part of our environment, but under which circumstances do they become a risk? Endotoxins are a marker for an attack by gram-negative bacteria. Therefore, there is a regular controlled uptake of endotoxins by the gut epithelium in order to train the immune system. However, if higher amounts get inside the organism than the liver is able to immediately neutralize, they are going to be further disseminated with serious consequences. But first it is important to look at the circumstances leading to an increased uptake. As long as the endotoxins remain in the gut lumen, they do not stringently constitute a risk to animal health. This situation changes in case of an impaired gastrointestinal barrier being unable to keep up its shielding function. The following factors may impair gut integrity, leading to an increased permeability of the gut: X Inflammatory processes caused by pathogens, dysbiosis or mycotoxins X Ischaemia (reduced blood flow) for example due to heat stress X Cytotoxic effects of mycotoxins Already at low concentrations, mycotoxins constitute a particular threat to gut integrity. They inhibit the protein biosynthesis, cause oxidative stress, and some of them, such as deoxynivalenol (DON), even manipulate the gene expression of epithelial cells. So, it was shown in scientific studies, that DON reduced the forming of certain building proteins of the tight-junctions1. What are the consequences of an uncontrolled uptake of endotoxins caused by an increased gut permeability? The impacts of an increased uptake of endotoxins depend on the absorbed quantity and the affected animal species. Ruminants, pigs and horses for example are much more sensitive compared to dogs, rats or poultry. If the tolerated maximum dose per affected species is exceeded, a complex inflammatory response of organism occurs in the body. Consequently, not the endotoxin itself is harmful, but the severe reaction to it given by the immune system. The more endotoxins invade, the more devastating is the extent of this reaction. In case high quantities of endotoxins get into the blood circulation at once, this will lead to consequences affecting the entire organism. Lesions such as vascular damages, coagulopathies, haemorrhages and necrosis may finally lead to an endotoxin shock resulting in organ failure with potential lethal ending. But if there are latently arriving quantities of endotoxins, permanently overloading the buffer systems to a low to medium degree, that will lead to so called endotoxin associated diseases. These are shown by milder systemic reactions and more locally demarcated inflammatory lesions. The clinical picture may vary regarding the different animal species. In pigs for example the “Swine Inflammation and Necrosis Syndrome” (SINS) is related to endotoxin stress. The clinical signs may be shown in the form of Effect of mycotoxins on the gut epithelium
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