Acidosis (abnormally high acidity) in the hindgut (the large intestine and colon) can cause a number of problems in horses, including anorexia, colic, laminitis, and stereotypic (continuous, repetitive, and serving no purpose) behaviors such as wood chewing and weaving. Unfortunately, this is often a risk when feeding today's rich concentrate feeds, and it all goes back to the evolution of the horse's digestive system. That system was designed to process large amounts of high-fiber, poor-quality forage, rather than today's richer diets.

At the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla., Joe Pagan, PhD, president of Kentucky Equine Research in Versailles, Ky., presented the results of a study evaluating the efficacy of a protected sodium bicarbonate product in fighting hindgut acidosis. This problem is common in dairy cattle on high-grain diets, he noted, and sodium bicarbonate is often fed to combat the resultant drop in feed intake and milk production.

"Unfortunately, in horses raw sodium bicarbonate never makes it to the hindgut; it just buffers the stomach," he noted. However, Kentucky Equine Research, along with Balchem Corporation, has developed a protected form of sodium bicarbonate (PSB, product name EquiShure) that was the focus of the current study.

Six 5-year-old Thoroughbreds in training on a high-speed treadmill were split into control and treatment groups and studied. One group was fed 168 g of EquiShure (100 g of sodium bicarbonate; the rest is the encapsulation agent) daily for a four-week period, then the other group received the same treatment (the treatment and control groups were swapped for the second study period). All horses received a diet of unfortified sweet feed, timothy hay, and 50 g of loose salt. Blood and fecal samples were collected every two hours for eight hours on Day 15 of each period, and during week four, all horses wore a complete collection harness for five days so fecal and urine contents could be analyzed.


Fecal acidity increased in controls by six hours after feeding. In contrast, the horses receiving PSB had no significant changes in fecal acidity during the sampling period. Horses on PSB also had significantly higher absorption of fat and sodium. There was a trend toward increased digestibility of neutral detergent fiber (fiber content), hemicellulose (a plant cell wall polysaccharide), and fat, but these differences were not statistically significant.

One attendee asked if this product might have value for treating severe acidosis due to carbohydrate overload. Pagan explained the product was intended more for long-term maintenance than acute treatment, but he believes it might help and wouldn't hurt.

Those involved with racehorses might wonder if the levels of tCO2 (total carbon dioxide) were elevated in these horses' blood, as tCO2 is tested in Thoroughbreds to detect milkshaking (dosing with bicarbonate in an attempt to reduce lactic acid in the muscles and, thus, increase endurance). In this study tCO2 levels in horses getting PSB were not significantly different than the controls. While they were slightly higher than that of controls, the levels remained around 33 mmol/L; the testing cutoff for racing is 37 mmol/L.

"The PSB used in this study was effective in attenuating the hindgut acidosis that resulted from high-grain intakes in exercised Thoroughbreds," concluded Pagan. "More research is needed to evaluate how PSB supplementation affects intestinal epithelial health and integrity."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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