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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

The post Antioxidants For GGT Syndrome In Training Racehorses appeared first on Horse Racing News | Paulick Report.

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The Plants A Horse Eats May Cause Sun Sensitivity

A horse with pink skin that blisters and peels may be having a painful reaction to sun exposure – but it may not be sunburn, as many would assume. Instead of overexposure to ultraviolet rays, this reaction takes place internally — photosensitivity occurs when horses with large white patches of skin graze on Saint John's Wort or alsike clover. The photodynamic compound in the plants circulates in the blood. When the compound comes close to pink skin and is exposed to the sun's UV rays, a chemical reaction occurs that damages tissues.

Secondary photosensitivity occurs when a horse's liver is damaged and unable to filter the toxin from the bloodstream, causing the same reaction.

In photosensitive horses, the skin on any white area of their body can blister, including on their face, legs or body. After the blisters, tight scabs will form. These scabs eventually peel away in a lengthy, painful process. Though horses can be afflicted with all sorts of skin disorders, photosensitivity is an exceptionally painful one.

If crusts appear on the horse's skin, it's imperative to identify if they are only located on white markings. If the crusts cross a border into darker hair, photosensitivity is most likely not the culprit. If there's any question, a veterinarian should be called for the best course of treatment.

Affected horses are often removed from fields that may contain phototoxic plants and kept indoors until the skin heals.

Virus Believed To Cause Equine Liver Disease Found To Be Innocuous

Theiler's disease, which has been recognized in horses for the last 100 years, has long been believed to cause transmissible hepatitis, though the pathogen that causes it has never been identified. New research shows that the virus originally blamed for causing liver disease doesn't appear to be the cause at all–and that the suspected virus is virtually harmless.

Researchers discovered two novel equine pegiviruses (EPgV); EPgV-1 was not associated with disease and the other was identified as the cause of an outbreak of serum hepatitis in horses. That specific EPgV was dubbed Theiler's disease-associated virus (TDAV).

Drs. Joy Tomlinson ,Raphael Wolfisberg, Ulrik Fahnøe, Himanshu Sharma, Randall Renshaw, Louise Nielsen, Eiko Nishiuchi, Christina Holm, Edward Dubovi, Brad Rosenberg, Bud Tennant, Jens Bukh,Amit Kapoor,Thomas Divers, Charles Rice, Gerlinde Van de Walle, Troels Scheel used more than 20 types of tissue from horses being screened for the viruses to learn more about EPgV-1.

They found high viral loads in bone marrow, serum and the spleen; some lymph nodes and blood cells were positive, but liver tissue was not. The researchers concluded that the equine pegiviruses cause infections in horses, but not hepatitis. Bone marrow was identified as the primary site of replication for both viruses.

The researchers also noted that a newly discovered parvovirus seems to be responsible for multiple equine Theiler's disease cases.