For Good Endurance in Horses, Feed for the Right Gut Bacteria

A French study is the first to connect the gut microbiota with the mitochondria in horses, or any other species.
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Researchers took blood samples from 20 Arabians before and after one of several national-level French endurance races. | The Horse Staff

The feed horses eat can fuel their muscle power in more ways than you might think. According to a new study, muscle cells create energy based not only on available nutrients but also what the microorganisms in the gut—which vary according to what horses eat—tell them to do.

“There are some kinds of bacteria in the gut microbiota that favor the production of energy at a (cellular) level and which, consequently, could enhance performance,” said Eric Barrey, PhD, DVM, the Integrative Biology and Equine Genetics team leader at the National Research Institute for Agriculture, Food, and Environment (INRA), in Jouy-en-Josas, France.

The gut’s microbiome can have variable kinds of microorganisms from horse to horse, depending on how they’re fed, managed, and exercised, among many other factors. While studies have already shown how gut microbiota might affect a horse’s health, the new French study suggests these microorganisms might also affect their athletic ability.

By sending signals through compounds they produce, gut microbiota appear to affect the way the mitochondria—the “power plants” within each cell—generate energy. And when the gut has the right mix of microorganisms, its signals seem to code for optimized fatty acid production, oxygen use, reduced inflammation, and lowered blood sugar, Barrey’s team reported today in Frontiers in Molecular Biosciences.

he feed horses eat can fuel their muscle power in more ways than you might think. According to a new study, muscle cells create energy based not only on available nutrients but also what the microorganisms in the gut—which vary according to what horses eat—tell them to do.

“There are some kinds of bacteria in the gut microbiota that favor the production of energy at a (cellular) level and which, consequently, could enhance performance,” said Eric Barrey, PhD, DVM, the Integrative Biology and Equine Genetics team leader at the National Research Institute for Agriculture, Food, and Environment (INRA), in Jouy-en-Josas, France.

The gut’s microbiome can have variable kinds of microorganisms from horse to horse, depending on how they’re fed, managed, and exercised, among many other factors. While studies have already shown how gut microbiota might affect a horse’s health, the new French study suggests these microorganisms might also affect their athletic ability.

By sending signals through compounds they produce, gut microbiota appear to affect the way the mitochondria—the “power plants” within each cell—generate energy. And when the gut has the right mix of microorganisms, its signals seem to code for optimized fatty acid production, oxygen use, reduced inflammation, and lowered blood sugar, Barrey’s team reported today in Frontiers in Molecular Biosciences.

Mighty Mitochondria: In-Cell Energy Producers With Minds (and DNA) of Their Own

Mitochondria are one of many organelles (specialized cell parts) within each cell that keep it alive and functioning. But mitochondria are special: They’re the only organelles with a double membrane and, more importantly, they’re the only ones with their own (smaller) DNA separate from the DNA of the cell (which is “the” DNA of the whole animal).

These cellular power plants apparently receive signals through metabolites—the small molecules created when bacteria in the gut break down and transform bigger molecules from the food that enters the digestive tract. And when they get these signals, mitochondria change the way they produce energy according to the kind of message that’s in those signals, Barrey said.

800 Genes Involved in Regulating Mitochondria Activity Over an Eight-Hour Race

The study is one of the first to connect the gut microbiota with the mitochondria in horses or any other species.

Barrey and his colleagues made the discovery when they took blood samples from 20 Arabians before and after one of several national-level endurance races (from 120 to 160 kilometers, around eight hours) held in Fontainebleau, France. They also took fecal samples from the horses just before the race to sequence the microorganisms living in their guts.

They noted that of the around 6,000 genes activated by the horses’ DNA during the race, 801 genes had some connection with making the mitochondria functional, he said. They used sequencing to compare this activation profile with the horses’ microbiota profiles to identify the different species of microorganisms. Because horses’ microbiota can vary considerably depending on a variety of factors, they wanted to see what the specific microbiota profiles of high-level endurance horses were.

Lachnospiraceae and Others Favor Delayed Inflammation and Low Blood Sugar

The horses’ profiles indicated that the microbiota were sending molecular signals to the horses’ mitochondria in their blood—and probably to their muscles, brain, lungs, kidneys, and other organs vital to physical effort as well—regulating the aerobic power they were producing. Specifically, they seemed to send signals that slowed the onset of muscular fatigue, low blood sugar, and inflammation (which can make muscles feel tired and sore), Barrey said.

When the scientists looked at these horses’ gut microbiome, they identified which bacterial families were likely sending performance-enhancing signals to the mitochondria. Essentially, these were the bacteria capable of creating the right signal, through a metabolite called butyrate. Butyrate is a fatty acid already known for its role in energy production.

These butyrate-producing bacteria include Lachnospiraceae (Oribacterium, Butyrivibrio, Agathobacter and Eubacterium spp.), Ruminococcaceae, Spirochaetaceae (Treponema spp.), and Rikenellaceae.

Importantly, the microbiota don’t appear to influence the horses’ anaerobic power, however. Horses—like all mammals—have two kinds of energy: One (“aerobic”) comes from the oxygen available in the blood at any time (mostly from breathing). The other (“anaerobic”) is the energy production that kicks in when there’s not enough oxygen available at the peak of exercise power—a sort of “reserve.” (There might be more oxygen a few seconds later at the next breath.) Anaerobic energy is more common in short, fast sprints like track races; endurance racing, however, usually occurs at slower speeds (20-22 kilometers/hour) that allow horses to keep up a pace of oxygen supply that maintains the use of aerobic energy, without having to dip into the anaerobic energy.

Feeding the Right Endurance Bacteria: Let Them Eat Hay!

In practice, these study findings could support a forage-forward diet.

“Hay, hay, hay!” Barrey said. “Hay is magic.”

While some managers tend to feed sport horses high amounts of concentrated feeds in hopes of increasing proteins and carbohydrates, such a diet might go against what’s best for the microbiota of performance horses—at least those needing a lot of endurance. “Good-quality hay likely favors the proliferation of the right microbiota,” he said.

That said, it’s important to have balance with some concentrated feeds that can provide necessary proteins and carbohydrates, as well as a few lipids (fats), he added. While his study did not delve into this analysis, he hopes further research can lead to feeding recommendations for optimizing the sport horse microbiotas.

Mitochondria: Ancient Bacteria?

While the discovery of this microbiota-mitochondria connection is exciting, it’s—in a way—not surprising, said Barrey. In humans, scientists have already noted that some kinds of mitochondria-related diseases, such as Crohn’s and Parkinson’s, are linked to the patient’s microbiota profile.

And on a more microscopic (and ancient) level, scientists have long suspected that mitochondria started out as independent bacteria 2.5 billion years ago. In theory, they later joined up with other microscopic cellular components to create the first mitochondrial network in a cell, Barrey said.

“It’s probably because of this ancestral origin that there’s this connection between the microbiota—which is made up mostly of different kinds of bacteria—and mitochondria,” he said.

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Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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