Leaky Gut Can Cause Costly Inflammation

Friday, September 25, 2026

The gut plays an important role in the immune system

By Emily McKinlay

Leaky gut, or damage to the gut barrier, is difficult to monitor in a commercial dairy setting, but recent research from the University of Saskatchewan suggests that everyday management-related stressors can affect the integrity of cattle’s rumen and intestines. These changes can affect the health and productivity of cattle, including reductions in milk yield.

During her PhD at the University of Saskatchewan, Dr. Claire Bertens studied new strategies to measure gut barrier function in dairy cattle and how it is affected by management and nutrition.

“The gut barrier is the protective lining of the digestive tract of all species,” says Bertens.

“The cells lining the gut act as a selective wall, allowing nutrients, water, and electrolytes to be absorbed, while keeping harmful microbes and toxins from crossing between cells and entering the bloodstream. The gut essentially separates the animal’s internal organs from the outside environment.”

The cells of the digestive tract have proteins that tightly join neighbouring cells together to create this barrier. In ruminants, the rumen and the intestines have different mechanisms for maintaining gut barrier function.

“Leaky gut is a hot topic. There is more research suggesting that common stressors cattle experience and the associated production losses have a common outcome of compromised gut barrier function,” says Bertens.

“Especially over the past two decades, there has been a paradigm shift in our perception of what the gut does. It goes beyond the fundamental goals of digesting feed and absorbing nutrients, and includes promoting animal health and productivity by maintaining a robust barrier.”

When the gut barrier is damaged and function is compromised, toxins and pathogens can enter the bloodstream, causing inflammation that can lead to production losses.

“Cattle are constantly exposed to toxins and harmful compounds. When the gut barrier is compromised, these can cross between the cells and enter the bloodstream, causing local and systemic inflammation, which we refer to as leaky gut,” says Bertens.

“The gut is actually a major immune organ, and houses 75 per cent of the cow’s immune cells. Disruption of the gut barrier can trigger local and systemic immune responses. When the immune system is activated, nutrients — especially glucose and amino acids — are redirected away from growth, milk synthesis, and reproduction, and towards supporting the activated immune system.”

Bertens cites a study by Dr. Lance Baumgard, a professor at Iowa State University, in which his lab estimated that the activated immune system uses two kilograms of glucose in a 24-hour period. In dairy cattle, glucose is a primary driver for lactose synthesis and milk volume. With 72 grams of lactose required to produce a litre of milk, the glucose demand of an immune challenge can reduce milk yield.

There are many factors in farm management that can contribute to the development of leaky gut.

“I think of the factors that may affect gut integrity of dairy cattle in buckets. The first bucket includes environmental stressors like heat stress, cold stress, and high pathogen load. The next bucket is dietary stressors including abrupt diet changes, highly fermentable diets, and moulds and mycotoxins,” says Bertens.

“The third bucket is disease and disorders like mastitis, metritis, lameness, pneumonia, and ruminal acidosis. Disease, even in other organs, may affect gut integrity. The fourth bucket is social stressors such as weaning and pen changes. The fifth is management-related stressors, such as overcrowding, bunk space, low feed availability, transportation, cow comfort, vaccination, and time away from pens. The final bucket is the transition period or the time around calving, which is often a time of stacked stressors.”

Bertens adds, “Although a lot of these stressors seem different, there is now more research suggesting that the production- associated losses observed with these stressors are connected through a common pathway of leaky gut.”

To better understand where in the digestive tract leaky gut occurs and how it is affected by various stressors, Bertens used indigestible compounds called ‘markers.’ The study used cows with ruminal cannulas — surgical devices that allow direct access to the rumen.

“Dr. Greg Penner and I developed a dual marker technique to understand where leaky gut is occurring in cattle. We deliver two different indigestible markers into two areas of the digestive tract. One marker is delivered directly into the abomasum as an indicator of intestinal leaky gut, and simultaneously, the other marker is delivered into the rumen for total tract indication of leaky gut.

“The markers are large, not digested or metabolized, and are not transported across the gut. Therefore, if the gut is leaky, more of the marker will cross from the gut into circulation. We can then measure marker appearance in blood or urine, giving us an idea of regional gut barrier function.”

The research team then used this technology to measure leaky gut during common stressors and to evaluate prevention strategies.

The first stress event was a feed restriction model that provided 40 per cent of what the cow would typically consume per day for five days. This model simulates events such as limited feed availability at the bunk, transportation events, weaning, disease, or heat stress.

“This is a common model used to understand how offfeed events affect gut health.

“We saw a greater effect on the intestinal region, with over 60 per cent of the leaky gut occurring in the intestines. These findings support other work done within and outside of our lab group. However, for the first time, we were able to differentiate which region of the gut is affected during periods of low feed intake.”

The next study used heat stress in a Western Canadian context as the challenge. They also used dietary strategies to help mitigate the negative outcomes of heat stress on gut barrier health.

“Heat stress is a challenge that we know will cause leaky gut, but we didn’t know where in the gut it occurred. In our study, we found that 72 per cent of leaky gut occurs in the intestines during heat stress.”

Dietary supplementation of calcium magnesium carbon ate was able to reduce leaky gut by 27 per cent when included at one per cent of the diet, or around 250 grams per cow. This may offer a targeted opportunity to protect the intestinal regions during heat events.

The final experiment used the markers to assess leaky gut during mastitis — inflammation in the mammary gland — to understand how the gut barrier responds to disease challenges. The team also fed a probiotic-postbiotic blend during the challenge to see if it improved gut barrier function during the health event.

“We observed that inflammation was greatest and feed intake was lowest 24 hours after the challenge; however, total tract and intestinal leaky gut were reduced 24 hours after the mastitis challenge, and the intestinal impact lasted up to six days after the challenge. The probiotic blend didn’t affect the response.”

“These findings were opposite to our hypothesis. During disease, cattle experience local and systemic inflammation and go off feed, which we expected would increase leaky gut. However, this was the first time in research where an infection model was applied, and leaky gut was evaluated.”

While Bertens’s study didn’t assess the cause of this result, she hypothesizes that the reduction in leaky gut could be a protective mechanism of the gut to limit further pathogen exposure when inflammation occurs in another organ.

Bertens’s research focused on determining the location of leaky gut under different stressors, but ideally, management would minimize stress events to promote gut barrier health and prevent damage.

“Compromised gut barrier function and potential immune activation are energetically expensive. It moves resources away from production and towards the immune system. Producers need those nutrients to go towards processes that will make them money. Good management to reduce stress is probably the most effective way to prevent leaky gut on-farm. Avoid overcrowding and provide adequate bunk space, ensure feed and clean water are always available. In addition, feed additives are available that can be used to help support gut health.”

She also recommends cattle have access to high-quality feed and balanced diets, comfortable stalls with sufficient bedding, and heat abatement during summer. Minimizing pathogen load and avoiding multiple stress events close together can also help prevent leaky gut.

While the gut barrier continues to gain attention among nutritionists, researchers, and veterinarians, it remains difficult to measure in a commercial setting. Bertens’s research presented a new technique for identifying regional differences of leaky gut, but it requires ruminally-cannulated animals, making it inapplicable for day-to-day farm use.

“There are other indirect tools to help diagnose leaky gut, such as dry matter intake consistency, changes in milk composition, manure consistency, rumination activity, and blood inflammation markers, but there is currently no direct tool that we have to measure leaky gut on-farm,” says Bertens.

Now that Bertens’s work has identified the locations of leaky gut under different stress conditions, she hopes that interest in gut barrier function will lead to the development of diagnostic tools that nutritionists and veterinarians can use to troubleshoot gut-related challenges. BF