Leaking Profits Through the Gut

Livestock | December 2025

Written by:

Jennifer Ryan has been writing about veterinary topics for nearly 20 years. She has a master’s degree in journalism, a bachelor’s degree in agricultural communications and decades of experience caring for both livestock and pets.

Key Points
  • The gastrointestinal tract is one of the most metabolically active tissues in ruminants, accounting for approximately 20% of their oxygen consumption and 30% of metabolic processes and protein synthesis.2
  • The gastrointestinal epithelium is a layer of cells that lines the entire digestive tract.
  • This layer has three important functions: Controls nutrient absorption, metabolism, and delivery of nutrients to other body tissue.2
  • The mechanisms controlling gastrointestinal epithelium responses, especially in the lower gut, are poorly understood.2
  • Common stressors like disrupted feeding schedule or heat stress can cause a leaky gut.
  • The signs may include reduced feed intake, increased susceptibility to disease and/or reduced productivity.

The gastrointestinal tract (GI) of cattle has a big job to do: Take in nutrients and power productivity. During this process, the gut is exposed to beneficial nutrients as well as harmful toxins and other substances. This can make the gut a potential source of inflammation and losses.

“The GI system is a crucial barrier,” explained Erin Horst, Ph.D., dairy technical consultant, Elanco Animal Health. “It’s basically just a tube, and the inside of that tube is exposed to the external environment. Some of those substances can be beneficial and some detrimental. The barrier serves a crucial role of absorbing the nutrients the animal needs while keeping the harmful toxins and bacteria from crossing the barrier.”

When the gut barrier fails, bacteria and other harmful substances may leak into the animal’s body, resulting in inflammation. Any time cattle divert resources towards addressing inflammation, they are not optimally efficient or productive, Horst noted.

A Greater Role Than Just Digestion

Between 70% and 75% of the immune system resides within the gut. If the physical barrier of the gut fails, immune cells step in. When the damage to the gut barrier is extreme, these protective mechanisms fail and pathogens can enter into systemic circulation; the gut becomes leaky.

The rumen epithelium is thicker than the lower gut of cattle. A thinner barrier makes the hindgut possibly more susceptible to leaking.

“The gut barrier is protected by physical barriers including a mucus layer just above the epithelial cells, which prevents harmful bacteria from harboring close to the cell layer,” Horst said. “In addition, the epithelial cells lining the
gut are connected to one another by
tight junction proteins, which act as the Velcro between cells to create a selective barrier that allows for absorption of nutrients and prevention of harmful bacteria from crossing.”

Only certain things get through. However, when animals are exposed to stress, those barriers break down. Sometimes, bacteria can bypass the barrier.
Even then, there is a second layer of protection. The immune cells in the gut become active after physical barriers fail. In stressful situations, pathogens can overwhelm the system and enter the bloodstream or even organs like the liver. The result is systemic inflammation.

This inflammation prompts a full-body immune response – pulling energy away from growth or milk production and to the immune system.

“The immune cells require energy, specifically glucose,” Horst explained. “This is important for lactating animals because we know how important glucose is for making milk.”

In fact, Iowa State University researchers intentionally administered a gamma-secretase inhibitor (GS) that reduces intestinal barrier function to Holstein cows. They found the cows receiving the inhibitor showed 66% reduced dry matter intake and a steady decrease in milk yield.1

Stress Factors That Can Cause Leaks

Even small stressors can cause the gut to become leaky. Cows love routine. When those routines become disrupted, the animal can become stressed. The factors that can cause leaky gut can be large events or small management changes, including:

  • Overcrowding in pens
  • Running out of feed
  • Heat stress
  • Cold stress
  • Disease challenges
  • Toxins in feed

“In a research setting, we’ve found that systemic inflammation and reduced productivity occur in response to feed restriction events, which we know can often occur in real world settings,” Horst said. “In fact, even just 12 hours of feed restriction can cause losses to milk likely stemming from leaky gut and the resulting inflammation.”

In addition to changes in feeding schedules, heat stress can constrict blood flow to the gut and reduce barrier function.

Producers know that disruptions, disease and weather events can result in productivity losses. Today, understanding the reason behind these losses can help emphasize the importance of reducing stress and supporting gut health.

Sneaky Leaky Gut Signs

Producers should be aware the signs of a leaky gut aren’t always clinical.

“Often times animals will experience reduced feed intake and milk production, which can be difficult to detect at the herd level,” Horst said. “Of course, any time cows are impacted by stress, certain animals are more affected than others depending on the stage of lactation or the unique set of stressors they may have been exposed to.”

Preventing Gut Barrier Failures

Unfortunately, experts cannot immediately walk onto a farm and definitively say animals are experiencing inflammation stemming from leaky gut. However, this additional knowledge increases the need to address stressors known to impact gut integrity such as overcrowding, limiting frequent pen moves, keeping feeding schedules consistent and gradually making diet changes.

“I always advise producers to start with what they can control and address those stressors,” Horst advised. “Cows love consistency. They even love to eat at the same spot along the bunk every day. It’s important to push feed every hour or two hours, make sure cows can access feed when it’s there and keep milking times on schedule.”

In addition, Horst recommends investing in heat abatement techniques like fans and sprinklers to reduce heat stress loads.

Finally, producers and nutritionists can add a bit of insurance by using feed additives that may help support GI health year-round. Mycotoxins can negatively affect gut health. One spot in the silage pile may have mycotoxins, while another is perfectly fine.

“There are binders to address mycotoxin challenges,” she recommended. “Feed costs are high, but flip the mindset and make an investment that puts you in a better position when the time comes.”

DSRs Offer Another Eye

Distributor sales representatives can offer a second look at management procedures when out and about on farms, Horst advised. There will always be a minimal level of stress arising from day-to-day functions. For example, pen moves and diet changes are a necessity. However, improved handling practices and upgraded equipment can help reduce stress.
“I never discourage a fresh set of eyes,” she said. “Make sure customers are aware of product options to promote gut integrity and address inflammation.”

References:

  1. Kvidera SK, Dickson MJ, Abuajamieh M, et al. Intentionally induced intestinal barrier dysfunction causes inflammation, affects metabolism, and reduces productivity in lactating Holstein cows. J Dairy Sci. 2017;100(5):4113-4127. doi:10.3168/jds.2016-12349
  2. Steele MA, Penner GB, Chaucheyras-Durand F, Guan LL. Development and physiology of the rumen and the lower gut: Targets for improving gut health. J Dairy Sci. 2016;99(6):4955-4966. doi:10.3168/jds.2015-10351

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