Ruminant Leaky Gut Syndrome: Performance Implications for the Ruminant Digestive System

Ruminant leaky gut syndrome is a multifactorial deterioration of the ruminant digestive system

Many factors can contribute to the maintenance of the ruminant intestinal barrier and therefore to the maintenance of all the functions performed by the ruminant digestive system. These parameters are interconnected and contribute to the overall performance of a healthy and functional ruminant digestive system.

• Environmental factors can play a part in altering the ruminant intestinal barrier creating intestinal permeability, including all the transitions periods: transportation and co-mingling, heat stress, calving, fattening, adaptation to a new diet, etc. (Amin N., Seifert J., 2021).
• The ruminant lower gut microbiota, which modulates the immune system and protects against enteric infections (Chase C., Kaushik R.S., 2019), makes a major contribution to maintaining the integrity of the ruminant intestinal barrier. Furthermore, any disturbance in the ruminant lower gut microbiota is likely to alter the homeostasis of the ruminant digestive system.

• Given that 70% of the immune system is in the ruminant digestive system, it is easy to understand that altered ruminant intestinal barrier functions can trigger excessive immune activation in the ruminant lower gut.
• The integrity of the ruminant intestinal barrier is doubly important, as it must enable the ruminant digestive system to perform its functions, such as: control nutrient absorption and protect the host from the mixture of microorganisms, toxins and chemicals (Steele M.A. et al., 2016). Tight junctions also play a key role in regulating ruminant lower gut permeability. This integrity allows for a reduced immune activation.

What are the consequences of ruminant leaky gut syndrome on ruminant digestive system performance?

Reduction of ruminant nutrient absorption

In order to understand the molecular and morphological effects of the ruminant leaky gut syndrome at the origin of the reduction in the absorptive capacity of the ruminant digestive system, an artificial ruminant leaky gut syndrome model was created following repeated injections of indomethacin (Cangiano L.R. et al., 2022).

Pictures of intestinal sections from calves exposed to intramuscular injections of saline (CTL) or 2.4 mg/kg of indomethacin (INDO-H) every 12 h, for 48 h (Cangiano L.R. et al., 2022)

The result is the reduction in villus length (36 and 32%) and surface area (34 and 26%) in the distal jejunum and ileum.​

Ruminant systemic inflammation

The penetration of undesirable molecules through the permeable ruminant intestinal barrier is likely to trigger an excessive immune response leading to sustained systemic inflammation (Vancamelbeke M., Vermeire S., 2017).

Breakdown of tight junctions, transport of pathogens and activation of inflammatory responses​ in mucosal surface of calves (from Amin N., Seifert J., 2021)

Such inflammation results in changes in tissue function that ultimately shifts the metabolic priorities of the animal to support the increasing energy demand of the immune system, which negatively affects growth and productivity by a specific energy partititioning.