Linking rumen disorders to immunity in cattle: old and new paradigms

Maintaining a healthy rumen ecosystem is crucial to avoid systemic disorders in cattle, but also critical to ensure that milk and meat are produced from healthy animals in an efficient and cost-effective manner. In fact, today’s intensive management systems of cattle typically encourage the inclusion of large amounts of easily degradable carbohydrates in the diet to support rapid weight gain or high milk yields, and enhance cost efficiency. Although these feeding practices are useful to maximize production in a cost-effective manner, they do not cope with the digestive physiology of cattle. Therefore, rumen acidosis, and in particular its subacute form, is one of the most prevalent animal health and welfare issues in intensive cattle production systems. New data indicate that rumen acidosis may leads to severe dysbiosis and the release of bacterial compounds, with immunogenic properties, which also adversely affect the host. One of these compounds is endotoxin or lipopolysaccharide, a component of the outer leaflet of the external membrane of all Gram-negative bacteria. This mini-review will primarily focus on rumen acidosis, trying to link this “old” metabolic disorder of cattle to more “new” paradigms that imply an association between rumen acidosis and endotoxin with other metabolic disorders of cattle. It is clear that the more we know about the metabolic adaptive capacity and health status of the rumen, the better we can shape our future feeding strategies for more efficient and healthy ruminant production.