kentucky equine research | Horse Racing Free Tips

Bone Adaptation In Growing Foals

Mechanical loading strengthens bone during growth, so exercise during childhood and adolescence has been shown to have lifelong benefits on skeletal health in humans. Similarly, exercised foals show greater bone size and strength, and resistance to bending and torsional distortion, compared to pasture-exercised control foals.¹

Because the fetlock joint must withstand incredible forces, high-performance horses, including Thoroughbred and Standardbred racehorses, often sustain injuries at this site. The joint connects the long and short pastern bones, known also as the first and second phalanx.

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A recent study of sound Standardbred foals, all trotting-bred, characterized how the long pastern bone adapts to changing loads during growth through the use of regular computed tomography (CT) scans during the first year of life. In addition to measuring strength and composition changes in the bone, researchers calculated strain energy density, a biomechanical metric of potential bone remodeling.²

Growth-related changes in mineral density and bone area at various bone points (distal epiphysis, mid-diaphysis, and proximal epiphysis) were assessed. These three points were further divided into four functional quadrants (dorsal, medial, lateral, palmar). Mineral density and bone area uniformly increased in the diaphysis and a portion of the proximal epiphysis, the medial quadrant, but not in the fracture-prone lateral quadrant. Strain energy density was constant during growth, indicating bone adaptation to standing quietly, the primary activity of Standardbred foals, according to prior observation by researchers, which revealed that foals between the ages of two and five months spent 80 percent of their time at a standstill.

In sum, “the work provides a baseline longitudinal characterization of normal remodeling of the equine forelimb first phalanx during the first year of life and its effect of strain energy density,” the researchers explained. “This is an essential prerequisite to making evidence-based recommendations for training regimens that may encourage bone growth in areas prone to fracture during development. A properly prepared musculoskeletal system may lead to fewer fractures, thus reducing the unnecessary wastage of equine athletes.”

In addition to exercise, proper nutrition of the mare throughout gestation and of the foal during all growth phases fosters future soundness. “Nutritional management of young horses starts with an appropriate, good-quality forage. Fortified concentrates can then be fed to meet energy, mineral, and vitamin shortfalls,” said Catherine Whitehouse, M.S., a nutrition advisor at Kentucky Equine Research.

“Aside from hay and concentrates, supplements designed to increase bone health can be used to support young athletes. Triacton, a supplemented formulated by Kentucky Equine Research, contains a novel source of calcium and an array of bone-building nutrients designed to increase bone density, with the ultimate goal of promoting long-term soundness,” she explained. “Research in weanlings, for example, showed that Triacton had a positive effect on density of the cannon bone.”

¹Firth, E.C., C.W. Rogers, P.R. van Weeren, A. Barneveld, C.W. McIlwraith, C.E. Kawcak, A.E. Goodship, and R.K.W. Smith. 2011. Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals. Veterinary Journal 190:383-389.

²Moshage, S.G., A.M. McCoy, J.D. Polk, and M.E. Kersh. 2019. Temporal and spatial changes in bone accrual, density, and strain energy density in growing foals. Journal of the Mechanical Behavior of Biomedical Materials 103.

Article reprinted courtesy of Kentucky Equine Research (KER). Visit equinews.com for the latest in equine nutrition and management, and subscribe to The Weekly Feed to receive these articles directly (equinews.com/newsletters).

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Research Update: Cellular Mechanisms Of Laminitis

An international group of researchers recently proposed a theory to explain the cellular pathways involved in the development of laminitis, including the role of apoptosis, a normal process of self-destruction that helps eliminate damaged, superfluous, or unwanted cells. Unfortunately, their data showed that apoptosis did not influence the development of laminitis. Had their hypothesis held, however, targeted treatments for laminitis may have followed.

Laminitis is the painful separation of the lamellar layers of the hoof, which often results in profound lameness, prolonged and expensive supportive care, and possible euthanasia. Despite extensive research in this field, many of the underlying mechanisms associated with the development of laminitis remain unclear.

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The abovementioned theory proposed that sepsis-related laminitis, such as that induced by carbohydrate overload and black walnut exposure, involves apoptosis of cells that bind the lamellar layers of the hoof. The integrity of those cells helps suspend the third coffin bone inside the hoof. Researchers suggested that apoptosis occurs early in the disease process, even before signs of lameness manifest. Specifically, they proposed that exaggerated inflammation occurring with the presence of bacteria in the bloodstream could serve as a source of free radicals, which are known to induce apoptosis.

To test their theory, the researchers used hoof samples from horses subjected to carbohydrate overload or exposed to black walnut extract. Both models induce lamellar inflammation and sepsis. “When the researchers counted inflammatory and apoptotic cells microscopically, no increase in apoptosis was observed during either the development phase of laminitis or at the time of lameness onset,” relayed Whitehouse.

Though disappointing, these results sent researchers back to the drawing board in search of other mechanisms that contribute to the development of laminitis.

Meanwhile, horse owners must continue to employ management and nutritional strategies that keep horses safe from the ravages of laminitis. “In addition to avoiding management triggers, ensure horses have adequate nutrients to support the well-being of all body systems, including the integumentary system, which includes skin, hair, and hooves,” explained Catherine Whitehouse, M.S., a nutrition advisor for Kentucky Equine Research.

“To dodge potential nutrient shortages, all horses should receive a fortified feed suitable for their energy needs,” she said. This feed may come in the form of a traditional textured or pelleted concentrate or it may come as a balancer pellet, which is often useful for horses that can maintain their weight on forages alone.

Horses with compromised hooves may require additional support in the form of a high-quality hoof supplement. “A comprehensive hoof supplement provides more than just biotin to foster hoof growth and integrity. In addition to diet, routine management such as trimming or shoeing plays a vital role in maintaining and achieving hoof health that will also serve the horse well in the face of a laminitis episode,” Whitehouse explained.

Chronic inflammatory conditions, like laminitis, often respond to supplementation with omega-3 fatty acids, especially DHA and EPA. The omega-3s found in certain marine-derived products, like EO-3, are more available to horses than those found in plant-based sources.

^*Catunda, A.P.N., G.E.S. Alves, F.O.P. Leme, A.M. Carvalho, B.S. Leise, P.J. Johnson, and R.R. Faleiros. 2021. Apoptosis in epithelial cells and its correlation with leukocyte accumulation in lamellar tissue from horses subjected to experimental sepsis-associate

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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Ask The Nutrition Experts: What Can I Do To Help My OTTB Gain Condition?

Question: My 8-year-old Thoroughbred gelding, Caboose, is thin, actually thinner than he was when he came off the track a year ago (ribs on full display). He's turned out for 14-18 hours a day and receives the following ration: five flakes of grass hay, 7 lb (3.2 kg) high-fat grain, 3 cups corn oil, 1 lb (0.45 kg) balancer pellet, 1.5 lb (0.7 kg) of a flax/rice bran supplement, and other supplements (biotin, digestive support, and devil's claw). He's in minimal work. We've investigated dental problems and gastric ulcer issues. Any suggestions?

Answer from Kentucky Equine Research: From my review, the current diet should be supplying appropriate nutrition for weight gain, if not oversupplying key nutrients. When body condition scoring him, is the visibility of his ribs your main concern, or is he lacking condition in general (topline, flanks, etc.)?

A description of the pasture would have been helpful here, as good-quality forage can have a significant impact on the horse's overall health and wellness. Providing free-choice access to good-quality hay and pasture often provides a large portion of the horse's caloric needs. When weight gain is needed, providing free-choice access to hay is recommended, particularly in cases of limited pasture.

With this in mind, five flakes of grass hay may not be supplying enough forage depending on the weight of the flakes and pasture availability and quality. Switching to a high-calorie forage, like alfalfa, would boost the number of calories derived from forage.

Another consideration is the amount of dietary fat in Caboose's diet, as you are feeding several high-fat feedstuffs (concentrate, corn oil, rice bran). Studies have shown a decrease in fiber digestion and utilization when large amounts of soybean oil were fed.

To simplify the feeding program but supply appropriate nutrition, I suggest reducing the number of feeds and supplements offered to just one or two. I would choose one energy-dense feed and feed that according to the manufacturer's recommendations. Because you are trying to increase Caboose's body condition, you will find yourself feeding close to the upper limits of those recommendations. It would not be unusual, for instance, to find yourself feeding 10-12 lb (4.5-5.5 kg) of feed daily or even a little more. Increasing meal size should be done slowly, over the course of 10-14 days.

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Offering a third meal will allow for smaller grain meals and will help maximize digestibility and feed utilization. Including a ration balancer is unnecessary when feeding 7 lb (3.2 kg) of fortified feed, resulting in overfeeding micronutrients.

Horses that struggle to maintain a healthy weight, despite receiving appropriate nutrition, often benefit from a daily digestive health product that supports optimal health and digestive function. EquiShure is one such product; it is a unique digestive buffer that features a protective coating to ensure its delivery to the hindgut.

EquiShure can help balance the support fiber digestion and potentially improve feed efficiency, ultimately resulting in weight gain. EquiShure can be fed along with your current digestive health supplement or you can consider using the total-tract digestive buffer RiteTrac as it contains both gastric support and EquiShure. Australian horse owners should consider these products.

For a horse in light exercise, this feeding rate is relatively high to not see improvement in weight and condition. Further consultation with your veterinarian may be needed to determine any underlying reasons for Caboose's elevated energy needs.

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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Antioxidants For GGT Syndrome In Training Racehorses

Blood analyses of Thoroughbred racehorses can reveal elevations in the enzyme gamma-glutamyl transferase (GGT). In what appear to be otherwise healthy horses, the significance of these high GGT values remains unclear. Using advanced metabolomic, viral and chemistry techniques, veterinarians suggest that “GGT syndrome” in fit racehorses could be related to oxidative stress.

“The horse's body produces excess GGT in the face of liver, pancreatic, and kidney disease, particularly injury to the bile duct. Concomitant increases in other liver enzymes, however, usually do not occur, suggesting that primary liver disease does not explain elevated GGT levels seen in racehorses,” explained Peter Huntington, B.V.Sc., M.A.C.V.Sc., director of nutrition, Kentucky Equine Research.

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Elevated GGT levels may be caused by:

Hypoxia (decreased oxygen reaching tissues);
Infection;
Toxicity (e.g., pyrrolizidine alkaloids from toxic plants);
Liver injury;
Hepatic glycogen depletion and repletion;
Overtraining; and
Oxidative stress associated with inadequate selenium or glutathione

Previous studies show that GGT levels tend to increase with racing frequency and cumulative training load and then decrease with recovery. This trend in GGT raises the possibility that oxidative stress and oxidative depletion play a role in the syndrome.

In a recent study, veterinarians collected blood samples from Thoroughbred racehorses.^* GGT values were analyzed, as were other liver values, selenium levels, viral load, and metabolomics. Comparisons were made between horses that did and did not have elevated GGT.

“Many of the potential causes of GGT syndrome were ruled out based on this testing, including viral hepatitis. One particularly interesting finding was that while selenium concentrations in horses with high GGT levels were within normal limits, they were significantly lower than selenium levels in horses with normal GGT,” noted Huntington.

These low selenium levels were reported in earlier studies and may reflect reduced antioxidant capacity related to oxidative stress. That said, one investigation found that selenium supplementation did not prevent increased levels of GGT in racehorses in training. In contrast, supplementation with the powerful antioxidant coenzyme Q10, such as Nano-Q10, can increase serum coenzyme Q10 levels.

“Racehorses in training with higher coenzyme Q10 levels had significantly lower GGT levels in one study. In addition, supplementation with EO-3, a marine-derived omega-3 fatty acid supplement, was associated with a significant reduction in GGT levels in horses in training,” Huntington said.

Overall, GGT syndrome is likely multifactorial rather than a result of a single mechanism, including oxidative stress. But, according to Huntington, there are some nutritional strategies that may be used to manage it, such as supplementing the horse's diet with antioxidants.

^*Mann, S., J.D. Ramsay, J.J. Wakshlag, T. Stokol, S. Reed, and T.J. Divers. 2021. Investigating the pathogenesis of high-serum gamma-glutamyl transferase activity in Thoroughbred racehorses: A series of case-control studies. Equine Veterinary Journal:13435.

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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