Cavities that form between the stratum medium and stratum internum of the hooves of racehorses are more likely to occur in the fore than the hind hooves, at the midline dead center of the toe, report Japanese researchers.
The team believes the results indicate that the primary cause of the hoof condition is traumatic damage to the hoof during exercise, when the horse disproportionately loads its weight onto the front feet.
This type of lesion - known as Gidoh in Japanese - is comparable to white-line disease that can develop into white-line disease-type Gidoh, write A Kuwano (Japan Racing Association, Tochigi) and colleagues in Veterinary Record.
They suggest that farriers "should remove the white-line disease by the hoof knife to prevent it progressing to Gidoh, even if it is a relatively smaller [lesion]."
The researchers assessed the prevalence of Gidoh at two farriery operations containing 5386 racehorses, 2.7% of which were affected by the hoof lesion.
Lesions were located in the fore hooves 84.0% of the time, with 43.8% of right fore hooves affected, 40.2% of left fore hooves, 8.2% of right hind hooves, and 7.8% of left hind hooves.
The majority of lesions occurred in the midline dead center of the hoof, at 59.2%, while 8.5% occurred in the medial heel, 6.3% in the medial wall, 6.3% in the lateral toe wall, 5.1% in the lateral wall, and 7.3% in the lateral heel, report Kuwano et al.
In multivariate analysis, the prevalence of affected horses was significantly associated with the training facility, as well as age, with a 43% increase in the risk for Gidoh per year of increasing age.
Regarding this latter finding, the authors note: "Training of older racehorses that win or perform well over numerous races usually involves considerable exercise, which routinely creates a stronger dynamic impact on the feet than in the cases of younger horses." This could explain hoof vulnerability as the horse ages, they contend.
The team could not explain the discrepancy between Gidoh risk at the two training centers, but estimate that the high prevalence of "long toe" at one center could have induced a higher incidence of "horny deterioration."
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