ISSUE FOCUS 38 FEED & ADDITIVE MAGAZINE August 2022 UNDERSTANDING ENDOTOXIN BEHAVIOR The mechanism of action is complex. Put simply, a lipopolysaccharide binds to a lipid-binding protein (LBP) to create the LPS/LBP complex that will eventually bind with Toll-like receptor-4 (TLR4). This triggers the signaling cascade for macrophage/ endothelial cells to secrete pro-inflammatory cytokines and nitric oxide that lead to the characteristic “endotoxic shock” (Figure 2). PRESENTATION OF ENDOTOXIC SHOCK Present in dust, feed, and feces, endotoxins are on every type of farm. However, different production species are not affected equally when it comes to LPS. While it is well documented that all animals have receptors for LPS, the way an animal reacts to the presence of LPS varies greatly. Poultry Of production animals studied, poultry is the least affected by LPS. Their sensitivity to LPS action is much lower than swine or ruminants. The theory for this is due to differences in the TLR4 receptor. Utilizing the lock and key concept, because the TLR4 activation sight responsible for endotoxin action is slightly different from mammals, it could partly explain the lower effects of LPS in poultry. Though there is little research, some possible signs of endotoxins in poultry are fatty liver, reduced feed intake, wet litter, and decreased performance; be it laying rate and shell quality, growth, or reproduction. Ruminants In ruminants, particularly dairy cows, LPS is extensively described as a factor of the subacute ruminal acidosis (SARA) pathological effect. Consumption of a high concentrate diet by dairy animals enhances the production of organic acids and results in lower pH values in the rumen and intestine. This decrease in pH affects, among other things, the equilibrium of the microbes in the rumen. The decline in pH perturbs the balance of the microbial population in the rumen to cause a substantial release of free endotoxin from gram-negative bacteria. During SARA, LPS is greatly increased in both the ruminal fluid and blood, triggering the pathology associated with SARA: metritis, laminitis, fatty liver, retained placenta, etc. Different studies have Figure 2: Lipopolysaccharides bind to lipid-binding protein and are carried to Toll-like receptor-4 where it is then absorbed into the circulatory system via the microvilli and intestine cell lining Journey of LPS binding and absorption
RkJQdWJsaXNoZXIy MTUxNjkxNQ==