This refers to pathological spaces which occur in the molar arcades, usually between the mandibular cheek teeth. The presence of a gap between the teeth allows food to accumulate and exert pressure on the gums resulting in periodontal pockets. This is extremely uncomfortable for the horse concerned and they have no way of clearing this packed food themselves. Invariably horses with diastema will ‘quid’, that is dropping their partly chewed hay/haylage on the ground.
Dental pain is one of the most common reasons for weight loss in horses. As horses are naturally inclined to eat they will continue to make an effort to do so until they are physically unable to. Identification of dental problems is best done at routine examination before it becomes symptomatic but if weight loss is already occurring then the situation is more urgent.