kentucky equine research | Horse Racing Free Tips

The Hindgut: Understanding Its Role In Equine Digestive Health

Horses rely on fermentation for optimal digestion of feedstuffs and energy production. Hindgut digestion, which occurs in the cecum and large colon, progresses most efficiently when horses are allowed continual access to forage and limited access to feedstuffs that could upset the pH of the cecum, including large grain meals.

Fermentation is achieved through the machinations of billions of protozoa, fungi, and bacteria. Together, these microbes convert carbohydrate-based contents, essentially plant-based fiber, into volatile fatty acids (VFA), which provide energy to the horse. If soluble carbohydrates, such as those found in large supply in grain meals, find their way into the hindgut, some lactate might be produced.

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An overproduction of lactate can shift the pH of the hindgut to a more acidic state, which may cause problems. When a drop in pH occurs, called hindgut acidosis, some of the beneficial fiber-digesting microbes die off. Digestive efficiency drops as a result. In many horses, this manifests as poor appetite, crabby disposition, recurrent colic, and onset of certain stable vices, such as stall-walking and cribbing.

To offset this, horse owners should scrutinize feeding management. Hindgut acidosis is rarely caused by what is fed but rather how it is fed. Here are three strategies to ward off hindgut acidosis:

Good-quality forage should be offered at all times, so the hindgut is continually in “processing mode.” Forage may be pasture, hay, or hay-based products such as cubes or pellets. Forage selection should be based largely on the nutrient needs of the horse.
Concentrate meals should not exceed approximately a half-pound per 100 pounds of body weight (5 pounds for a 1,000-pound horse).
If a horse requires more than 5 pounds of concentrate per day, divide total daily allotment into separate meals. Feeding three or four concentrate meals, evenly spaced throughout the day, is more beneficial to the horse than huge meals.

Some horses, especially those that are asked to perform intense exercise, must consume large grain meals to fuel performance. Hindgut acidosis can be curbed by feeding EquiShure, a time-released buffer that raises the pH of the hindgut and eliminates signs of acidosis.

Gastric Ulcers In Horses: Search For Biomarkers, Treatments Continues

Are you considering having your horse's stomach scoped again? Is there any other way to verify the presence of gastric ulcers? Right now, there isn't, but researchers are working on noninvasive ways to diagnose and monitor horses with equine gastric ulcer syndrome (EGUS).

Many performance horses have gastric ulcers, which are defects in the surface of the stomach lining that occur in either the glandular or nonglandular (squamous) regions. Thought to be largely due to management factors—stress due to training or competition, social isolation, diets high in concentrates or low in forages—gastric ulcers often cause poor performance, decreased appetite, and weight loss.

After diagnosing and grading ulcers via gastroscopy, veterinarians typically recommend treatments geared to decreasing the acidity of the stomach. Treatment plans for EGUS typically include diet modifications, management changes, and medications such as omeprazole, sucralfate, and ranitidine. Nutritional supplements designed to control the pH within the stomach could also be included.

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“Triacton supports gastric health by moderating acidity using ingredients shown to have greater buffering capacity. Those include a seaweed-derived source of calcium and several other highly bioavailable minerals,” said Catherine Whitehouse, M.S., a nutritionist for Kentucky Equine Research. “The form of calcium in Triacton offsets the negative effects of omeprazole on calcium digestibility compared to other commonly used sources of calcium in feeds and supplements.”

Because gastroscopies play a key role in ulcer management, repeated procedures are a necessary evil as horses may be resistant to treatment or the ulcers may return rapidly following cessation of pharmaceutical treatments like omeprazole.

Veterinary researchers recently suggested that identifying blood or salivary markers, or perhaps a combination of both, could help create a diagnostic panel for EGUS. This tool would screen patients for EGUS and monitor response to treatment, which would limit the frequency of gastroscopy.^*

Blood collected from eight mature geldings with gastric ulcers was evaluated for total antioxidant capacity. A moderate but significant correlation between blood and salivary antioxidant capacity was identified, potentially indicating that oxidative stress decreases as ulcers heal.

“The role of oxidative stress and antioxidants in EGUS requires further exploration, but these very preliminary findings suggest that antioxidants may play a role in the future management of this condition,” said Whitehouse.

While horse owners wait for this research to advance, Whitehouse suggested using diagnostics and treatments, including gastrointestinal buffers, currently recommended by veterinarians.

^*Svagerko, P., W. Bridges, E. Jesch, S. Pratt-Phillips, and K. Vernon. 2021. Equine gastric ulcers; a pilot study: Associated biomarkers and polysaccharide supplementation as a solution. Journal of Equine Veterinary Science 100:103518.

Reprinted courtesy of Kentucky Equine Research. Visit ker.com for the latest in equine nutrition and management, and subscribe to Equinews to receive these articles directly

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Tempting Tastebuds: How Taste Preference Is Measured Among Horses

How do feed manufacturers know horses will readily eat the products they produce? If the manufacturer works with Kentucky Equine Research, more than 30 years of palatability research is taken into consideration.

In this video, research coordinator Michael Sandwick explains the two-choice preference test and how it relates to product development. In these tests, horses are given two feed options in matching buckets, which are rotated daily. Initially, the horse is allowed to smell but not taste the feeds. The handler then turns the horse away from the buckets before releasing it to consume its preferred choice for three minutes. A scribe notes how many times the horse returns to the bucket, lifts its head, or gets distracted by outside factors. After three minutes, the leftover portions are weighed to measure how much of each feed was consumed.

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Sandwick got her start with the company as a summer intern. She is currently finishing her master's degree at Kansas State University while working at the Kentucky Equine Research Performance Center in Ocala.

Learn more about product development at Kentucky Equine Research.

Ins And Outs Of Transdermal NSAID In Horses

If you're fighting tooth and nail to administer oral medications, the introduction of a transdermal option often pleases horses and handlers alike. Transdermal medications are applied to the surface of the skin, typically in the form of an ointment or gel, so as to allow gradual absorption into the body. Are you considering transdermal medications, especially anti-inflammatories? If so, it's important to understand how these drugs are absorbed and eliminated, particularly if your horse is involved in competition and subject to stringent drug withdrawal times.

In the U.S., a transdermal formulation of the nonsteroidal anti-inflammatory (NSAID) diclofenac sodium, sold under the brand name Surpass, is approved for use in horses. Recently, a transdermal product containing flunixin meglumine was approved in cattle and is therefore available for off-label use in horses. Flunixin meglumine is often called by the common brand name Banamine.

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To assess how transdermal delivery of flunixin meglumine behaves in the body compared to other routes of administration (e.g., oral, intravenous, intramuscular), researchers applied a 10-mL dose of transdermal flunixin meglumine along the midline of the horse's back, from the withers to the tailhead. This was equivalent to a standard 500-mg dose of flunixin meglumine per horse. *

Blood and urine samples were intermittently collected for up to 96 hours after administration to measure the intricacies of how the medication is absorbed and cleared, a science known as pharmacokinetics.

“Transdermal application was well tolerated in all six study horses, with no horse showing any negative dermal effects,” said Peter Huntington, B.V.Sc., M.A.C.V.Sc., director of nutrition at Kentucky Equine Research.

In terms of the drug's behavior, here's what the research team found:

The maximum concentration of flunixin meglumine in blood was only an average of 515 ng/mL, which is much lower than oral and intramuscular concentrations. Oral administration of a comparable dose of flunixin meglumine results in average concentrations ranging from 3,340 to 7,200 ng/mL. Intramuscular flunixin meglumine reaches average concentrations of 1,799-3,269 ng/mL.
Transdermal absorption into the horse's bloodstream was slow, an average of 8.76 hours. Oral flunixin meglumine requires less than an hour to be absorbed.
Elimination (clearance) of transdermal flunixin meglumine was also much slower than other routes of administration. It took 22 hours for half of the drug to be eliminated from the bloodstream (called the half-life) when the transdermal formulation was used. In contrast, the intravenous half-life is 3.38-9.68 hours.
The data also showed that transdermal flunixin meglumine has unique pharmacokinetics called “flip-flop kinetics” in which the rate of absorption is actually slower than the rate of elimination.

“Based on this data, it is not surprising that flunixin meglumine and a metabolite were still detectable in urine 96 hours after application. This means that the withdrawal time for transdermal flunixin meglumine would be longer than for any other route of administration,” said Huntington.

He added, “Even though the blood concentrations of flunixin meglumine were lower compared to those achieved by other routes, the slow, variable absorption and 'flip- flop kinetics' indicate the medicine applied transdermally persists in the body longer than if given by other routes of administration. More excretion studies in exercising horses are needed before safe withholding periods before competition can be established.”

Despite the low circulating drug concentrations, transdermal flunixin meglumine still elicited an anti-inflammatory effect for up to 72 hours after application.

In terms of safety, Huntington warned, “Considering that transdermal flunixin meglumine is indeed absorbed systemically, this means that horses are at risk of the common side effects associated with NSAIDs administered by other routes: gastric ulceration, dorsal colitis, and disruption of the intestinal microbiome.”

Horses treated with any type of NSAID by any route of administration, including transdermal, would therefore benefit from a digestive tract supplement containing antacids, stomach-coating agents, and a hindgut buffer.

“These supplements reduce the risk of damage to the gut lining or change in the microbiota resulting from NSAID use,” Huntington advised.

*Knych, H.K., R.M. Arthur, S.R. Gretler, D.S. McKemie, S. Goldin, and P.H. Kass. 2021. Pharmacokinetics of transdermal flunixin meglumine and effects on biomarkers of inflammation in horses. Journal of Veterinary Pharmacology and Therapeutics:12993.

Reprinted courtesy of Kentucky Equine Research. Visit ker.com for the latest in equine nutrition and management, and subscribe to Equinews to receive these articles directly.

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