ISSUE FOCUS 48 FEED & ADDITIVE MAGAZINE October 2024 “The lipopolysaccharide content of the gut increases during acidosis and managing diets to reduce clinical and subclinical acidosis is beneficial. Increasing fibre content and reducing easily fermentable carbohydrates can reduce the likelihood of excess short-chain fatty acids or, in the case of clinical acidosis, lactic acid. However, energy requirements to maximise milk or muscle production may limit the extent to which diet manipulation can be employed.” The body has several physical barriers against “external” threats, including the skin, the respiratory linings, and the digestive tract. Of these three, the digestive tract faces the most potential threats, not only from ingested substances but also from what develops in situ, such as the growth of micro-organisms, the toxins they produce, and even the remnants of those that die within the tract. Both non-pathogenic and pathogenic bacteria commonly reside within the Gastrointestinal (GI) tract, with species like Salmonella and E. coli being typical examples of Gram-negative (G-) bacteria. This means that their cell walls do not retain the dye used during Gram staining. When Gram-negative bacteria lyse (both pathogenic and non-pathogenic), their cell walls break into segments that contain “endotoxins” composed of Lipopolysaccharides (LPS). Unfortunately, these LPS are highly reactive and send strong signals to the immune system, resulting in a pronounced inflammatory response. Lipopolysaccharides bind to TLR4 receptor sites, triggering a cascade of reactions that culminate in the production of pro-inflammatory cytokines. Furthermore, the absorption of LPS has been shown to reduce feed intake, exacerbating the issue, as animals experience increased energy requirements while available dietary energy decreases, leading to the utilisation of body lipids and a potential decline in body proteins. When the digestive tract is in a state of healthy homeostasis, the number of bacteria is kept “in check” and the host is able to cope with the endotoxins produced (due to natural bacterial cell death). However, disturbances in the diet or the diet itself can stimulate bacterial growth. Conditions such as subclinical and clinical acidosis can also cause excess death and lysis of bacteria. Diet composition can influence absorption; for instance, the lipid portion of LPS can combine with dietary fats, leading to increased absorption (Kelly et al., 2012). Additionally, factors such as heat stress and certain mycotoxins can weaken the cell-to-cell connections and the integrity of the gut, allowing greater absorption of LPS present in the digestive tract. Aside from its role in inflammation, LPS also has effects that can exacerbate or increase the risk of other metabolic diseases. Dairy cows infused with LPS show dose-dependent reductions in serum calcium concenLIPOPOLYSACCHARIDES – THE INTERNALLY GENERATED THREAT Bryan Miller Technical Business Manager – North America Volac
RkJQdWJsaXNoZXIy MTUxNjkxNQ==