Invisible Barriers: The Gut-Liver Axis and Its Impact on Ruminant Health

Intestinal health is a fundamental aspect of productivity and welfare in dairy ruminants. Historically, research on digestive health in ruminants has focused on the rumen, leaving the role of the small intestine and its interaction with the liver in the background. However, recent studies have shown that this axis is key to metabolic, immunological, and digestive regulation.

Despite its importance, its impact on milk yield has been little explored to date.

Recent trials have allowed for the first-time measurement of intestinal permeability in dairy cows, providing key information on the relationship between inflammation and productivity.

In this context, the use of botanical ingredients and microencapsulated organic acids has been studied as a strategy to improve intestinal integrity and modulate the inflammatory response.

THE INTESTINE-LIVER AXIS AND ITS IMPORTANCE IN RUMINANTS

In ruminants, the small intestine is not only responsible for nutrient absorption, but also acts as a selective barrier against pathogens and toxins. In turn, the liver plays a crucial role in gluconeogenesis, lipid metabolism, and detoxification.

Communication between both organs occurs through the enterohepatic circulation, a bidirectional system that allows the intestine to influence the liver and vice versa.

The liver secretes primary bile acids, immunoglobulin A, and angiogenin into the gastrointestinal tract, contributing to maintaining intestinal eubiosis and limiting the growth of pathogenic bacteria. In turn, the intestinal microbiota participates in the biotransformation of these primary bile acids into secondary ones, modulating their function and facilitating fat absorption.

When intestinal integrity is compromised, whether due to dietary changes, heat stress, or environmental factors, a phenomenon known as “leaky gut” occurs. This allows the passage of endotoxins and microbial products into the systemic circulation, generating an immune activation and a higher energy consumption for the inflammatory response, which negatively affects milk production and animal welfare.

The intestinal microbiota plays an essential role in the homeostasis of the intestine-liver axis.

Through the fermentation of dietary fiber, short-chain fatty acids, such as butyrate, are produced, which strengthen the intestinal barrier and provide energy to enterocytes.

However, alterations in the microbiota, caused by inadequate diets, diseases, or environmental changes, can favor the proliferation of pathogenic bacteria and the production of toxic metabolites that affect liver health.

FACTORS AFFECTING INTESTINAL AND LIVER HEALTH

In the face of these challenges, different nutritional alternatives have been explored to mitigate the impact of inflammation in ruminants.

Supplementation with botanical ingredients and microencapsulated organic acids has shown positive effects
on digestive health and hepatic metabolism in various species (Rossi et al., 2020; Fontoura et al., 2023) and have been proposed as an alternative to growth-promoting antibiotics in monogastric species (EFSA, 2012).

Organic Acids

Compounds such as citric and sorbic acid reduce gastrointestinal pH, limiting the growth of pathogenic bacteria and balancing the microbiota. Additionally, they modulate the expression of immune genes, improving resistance to infections.

Citric acid optimizes energy production in the Krebs cycle and reduces oxidative stress, while sorbic acid has antimicrobial properties that affect the viability of gram-negative bacteria, contributing to better digestive health.

BOTANICAL INGREDIENTS

Substances such as thymol and vanillin, have antioxidant, anti-inflammatory, and immunomodulatory properties,
strengthening the intestinal barrier.

Their phenolic compounds can inhibit the nuclear factor kappa B (NF-κB), reducing the production of pro-inflammatory cytokines and decreasing intestinal inflammation.

MICROENCAPSULATION

Allows these compounds to pass through the rumen without degrading, reaching the small intestine where they exert their effects.

Microencapsulation technology protects active ingredients from microbial degradation in the rumen and optimizes their release in the lower digestive tract (Lobo et al., 2023a,b).

RESULTS IN STUDIES WITH RUMINANTS

Recent studies conducted at Cornell University (United States) have demonstrated the positive impact of supplementation with botanical ingredients and microencapsulated organic acids on intestinal health and milk yield.

Preliminary trial in calves

In a study with calves exposed to heat stress, supplementation with botanical ingredients and microencapsulated organic acids improved dry matter intake (+200 g/animal/day) and weight gain (+100 g/animal/day) compared to the control group (Fontoura et al., 2023).

Trial in dairy cows

In mid-lactation cows subjected to heat stress conditions in a controlled environment, the inclusion of botanical ingredients and microencapsulated organic acids in the diet reduced intestinal permeability, measured through the plasma concentration of a paracellular marker (Cr-EDTA).

A lower presence of LBP (lipopolysaccharide-binding protein) and SAA (serum amyloid, acute-phase protein) was also observed, suggesting less endotoxin translocation and a better immune response (Sáinz de la Maza- Escolà et al., 2023).

In the same trial, an increase in dry matter intake (+1.4 kg/d), an increase in milk yield (+2.7 kg/d), and also an improvement in milk solids (Fontoura et al., 2022; Figures 1 and 2).

In field conditions under heat stress, the use of botanical ingredients and microencapsulated organic acids has been tested in various scenarios. In fresh cows, a decrease in rectal temperature (0.5 °C) and a significant increase in milk yield (+2.4 kg/d) were recorded, along with an improvement in milk protein (Sáinz de la Maza- Escolà et al., 2022). In mid-lactation cows, an increase in fat production and feed conversion efficiency was observed (Thomas et al., 2025). In dairy goats, an increase in energy-corrected milk and milk fat was observed (Giorgino et al., 2023).