Thrush is a bacterial infection of the horse's frog causing foul-smelling, black discharge and potentially significant pain if neglected. Prevention through regular hoof care is simple and effective.
Mild thrush is primarily a cosmetic and hygienic issue with limited welfare impact; severe thrush penetrating to the digital cushion or sensitive frog causes genuine lameness and pain. Neglected thrush can progress to white line disease and serious hoof structure compromise. The welfare harm is entirely preventable through routine hoof care — daily picking removes the wet, anaerobic conditions in which Fusobacterium thrives. Horses in clean, dry environments with regular farriery rarely develop problematic thrush even without specific treatment products.