The relationship between gut and liver health is referred to as the gut-liver axis. Evidence suggests that disturbances in the gut microbiota develop with intestinal permeability and bacterial translocation into circulation. This condition is commonly called ‘leaky gut’ which is characterized by heightened levels of bacteria-derived endotoxin in blood. In non-ruminants, endotoxemia represents a pathological mechanism of fatty liver. In dairy cattle, leaky gut develops in response to heat stress. The related rise in circulating endotoxin may explain why heat-stressed cows are at risk of experiencing hepatic steatosis and inflammation. Unfortunately, these detriments may compromise cow health, fertility, and milk production; however, our understanding of the gut-liver axis in dairy cows experiencing leaky gut is profoundly inadequate. Moreover, the dairy industry demands dietary therapies which increase nutrient absorption and intestinal barrier to combat leaky gut. Such applications have the potential to reduce economic losses to favor sustainability, especially when we consider the projected negative impact of climate change on the northeast dairy industry. In lactating dairy cows, we will determine whether heat stress-induced leaky gut develops with unique taxonomic differences in the gut microbiome, and whether these changes are related to endotoxemia and inflammation. We will also test the effects dietary organic acid (OA) and plant botanical (PB) supplementation, a promising new therapy that may enhance nutrient absorption and minimize intestinal permeability. Our study will involve feed, milk, blood, and fecal sampling, and the use of omics technology. Moreover, we will strictly adhere to an outreach plan to disseminate knowledge.
Project objectives from proposal:
Objective 1: Define the gut-liver axis in lactating dairy cows experiencing leaky gut. Rationale: The gut-liver axis involves the complex interplay between the gut microbiota, intestinal permeability, systemic endotoxemia, and liver health. In non-ruminants, microbial dysbiosis promotes leaky gut and compromises health, and heat stress modulates the gut microbiome in broilers. Therefore, heat stress likely changes the bovine gut microbiome in dairy cows experiencing heat stress and leaky gut.
Objective 2: Determine whether rumen-protected OA/PB supplementation prevents endotoxemia and liver injury in lactating dairy cows experiencing leaky gut. Rationale: Leaky gut increases circulating endotoxin to promote hepatic steatosis, inflammation, and activation of the acute phase response. Feeding rumen-protected OA/PB may reduce intestinal permeability to minimize these outcomes. Therefore, dietary OA/PB supplementation may be a practical approach to improve gut and liver health in dairy cattle.