ARTICLE 58 FEED & ADDITIVE MAGAZINE June 2023 as normal flora in the intestinal tract of humans and animals. Endotoxin is constantly shed from Gram-negative bacteria during multiplication through binary fission or when they die. Other potential sources of endotoxin contamination include water, feed, certain feed additives produced by E. coli (including vitamins and amino acids), faeces from farm animals, and the environment. ENDOTOXIN TRANSLOCATION AND SIGNALLING MECHANISM Endotoxins can translocate from the animal gut to the systemic circulation when the tight junctions between gut epithelial cells become compromised. This can occur due to dietary components, injury or stress. Additionally, endotoxins can translocate to the bloodstream from the mammary gland (Dosogne et al., 2002) and uterus (Mateus et al., 2003, cited in Eckel and Ametaj, 2020). The mechanism of endotoxin recognition starts when LPS-binding protein (LBP) binds to endotoxin, which then binds to CD14 molecules on the cell surface of immune cells. LBP-endotoxin-CD14 complex binds to the extracellular domain of TLR4MD2, a receptor for LPS predominantly expressed on immune cells such as macrophages and dendritic cells. This binding will cause TLR4 to activate a signalling cascade resulting in the production of mediators that produce the inflammatory response and recruit other immune cells to the site of infection. (Poltorak et al., 1998, O’Neill and Dinarello, 2000, Keating et al., 2007, Sun et al., 2004, Kim et al., 2007). ENDOTOXIN AND ANIMAL HEALTH Certain Gram-negative bacteria can be pathogenic to animals and can lead to the inflammation of the uterus wall (Metritis) and inflammation of mammary glands and udder tissue (Mastitis). Endotoxins can also cause various health disorders, including fatty liver and ruminal acidosis. These conditions can result in a reduction in feed intake and subsequently decrease weight gain. In weaning piglets, endotoxin (lipid A) has numerous effects associated with infection. These effects include fever, changes in blood cell population, activation of macrophages, adjuvanticity (enhancement of immune response), and induction of various inflammatory mediators. Endotoxins are also implicated in the pathogenesis of oedema disease and endotoxin shock (van Beers-Schreurs et al., 1992). These conditions are characterized by severe inflammatory responses and can have detrimental effects on the health and well-being of piglets. In a study conducted by Parra and colleagues (2011), the effect of endotoxin on the intestinal villi of swine was investigated. The study concluded that endotoxin had a negative impact on the morphology of the intestinal villi. Specifically, it resultFigure 2. Chemical structure of lipid A. of (A) Escherichia coli and (B) Bacteroides fragilis. Adapted and modified from (Weintraub et al., 1989) and (Rietschel et al., 1993).
RkJQdWJsaXNoZXIy MTUxNjkxNQ==