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Leaky gut: A journey through causes and consequences to mitigation

Progressive Dairy Editor Emma Ohirko Published on 30 June 2022

The gastrointestinal (GI) tract is a tube that runs from the mouth to the anus, fulfilling its vital role as a barrier to protect the rest of the body from things like parasites, toxins, acids and antigens that may otherwise cause damage outside of the GI tract.

In the presence of leaky gut, an immune response is stimulated by one or more of these things permeating other parts of the body.

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During his presentation at this year’s Rendez-vous laitier held by L’Association québécoise des industries de nutrition animale et céréalière (AQINAC), Lance Baumgard, a Norman L. Jacobson Endowed professor of nutritional physiology at Iowa State University, led attendees through the causes, consequences and target mitigation strategies to maintain gut barrier function and limit GI tract damage and immune activation to ensure a successful transition period. This article and accompanying infographic detail some of the highlights of Baumgard’s presentation.

Leaky gut

Click here or on the image above to view it at full size in a new window.

Immune activation

There are a variety of factors that negatively affect gut barrier. Some common factors in dairy cows are heat stress, reduced feed intake and increased inflammation, especially during the transition period. Each of these factors are often accompanied by decreased milk yield, poor reproductive performance or subclinical and clinical disease.

“Every single cow during the transition period has some magnitude of immune activation,” Baumgard noted. The source of this immune activation and subsequent inflammatory response is commonly attributed to the mammary gland and uterus. However, Baumgard argued the GI tract is also a source of immune activation from pre- to post-calving. Immune activation during the transition period plays a key role in various negative phenotypes, including suboptimal dry matter intake (DMI), ketosis, hypocalcemia and poor reproduction. Many of these outcomes have cascading impacts, becoming more visible over time. For example, feed restriction causes intestinal hyperpermeability and has been shown to reduce milk yield by as much as 22% in six hours.

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Increased inflammation is found to precede clinical disease by one week or longer. According to Baumgard, immune activation provides a look at the animal’s long-term productivity. “Post-calving inflammation is incredibly predictive of future success,” he said.

For optimal production and profitability, Baumgard recommended a strict feeding schedule that ensures cows always have access to feed. Taking the steps to reduce the risk of feed withdrawal is one thing producers can do to prevent something Baumgard described as an “on-farm scenario that compromises the integrity of the gut.”

Glucose and calcium

A cow with an activated immune system will use approximately 1 kilogram of glucose every 12 hours. As a precursor to lactose, glucose is strongly connected to milk yield, and increased glucose needs by the immune system can negatively impact profitability. Thus, understanding glucose requirements is a prerequisite to immune activation mitigation strategies.

All transition dairy cows experience immune activation which is (at least in part) responsible for the hypocalcemia that occurs for 48 hours post-calving. In dairy cows, two types of subclinical hypocalcemia have been observed. The first occurs in high-production, otherwise healthy cows; this is considered normal. The second type is associated with inflammation and often infection. In this scenario, the cow seeks to sequester endotoxins into lipoproteins for removal via a non-immune system route (a non-inflammatory route) of detoxification.

Mitigation strategies

To mitigate leaky gut in dairy cattle and thus prevent immune activation and its consequences, there are several direct and indirect actions producers and nutritionists can take to target GI tract health, especially during the transition period. A successful transition period should be devoid of lipopolysaccharides (LPS), excessive ketone synthesis and fatty liver, and prevent the redirection of glucose to the immune system. “If we remove this immune activation, she will eat, she will milk, and she will be profitable,” Baumgard concluded. end mark

ILLUSTRATION: Illustrated by Sarah Johnston.

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