There is a need for specific data on equine mastication in several fields: (1) In nutritional science, the disruption of the forage is crucial to sufficient energy uptake in the horse (Frape 1990). (2) In mandibular/oral surgery, knowledge about the motions of the jaws and about chewing forces is necessary for the development of techniques and materials for the treatment of mandibular fractures and malformations. (3) In equine dentistry, physical data about mastication are required for investigations of the resilience of the tooth, the periodontal ligament, and the materials used for therapy. The movements of the equine jaws during feeding have been documented by video analysis (Collinson 1994). Chewing has been defined as a unilateral process performed either on the right or on the left side of the mouth. One chewing cycle comprises three distinct phases (Collinson 1994, Tremaine 1997, Baker 2005): (1) opening stroke: the mandible moves downwards and to the side (Fig. 1a); (2) closing stroke: the mandible moves upwards until the lower jaw teeth make contact with the maxillary teeth (Fig. 1b); (3) power stroke: the lower jaw teeth grind upon the upper jaw teeth in a lingual direction (Fig. 1c). Pferdeheilkunde 22 (2006) 1 (Januar/Februar) 12-16