Hindquarter Movement of Sporthorse Stallions During Semen Collection

Some stallions used for both breeding and show jumping perform less well in competitions during the breeding season. It has been suggested that the demands of semen collection on the back and pelvis may impair the range of motion (ROM) required for show jumping. To better understand hindquarter dynamics, this study assessed the ROM of the hindquarters during both the mounting phase (MP) and ejaculatory phase (EP) of semen collection and compared it to the ROM previously measured during show jumping. The kinematics of six warmblood stallions were studied during semen collection on a phantom. Skin markers were placed on the withers, tuber coxae, proximal femur and tibia, and distal tibia and metatarsus. During each phase, six angles were measured using recordings made with a home-video camera (60 Hz) positioned perpendicular to the phantom. The differences in joint angles between the two phases were compared statistically using commercially available software. The pelvis showed a significantly larger ROM during the MP than the EP (P < .05). The ROM of the hindquarters was significantly larger during both the MP and EP than reported during show jumping, and the pelvis was considerably more extended (P < .05). This relatively extreme flexion and extension of the pelvis during semen collection may impose different strains on musculoskeletal structures which, combined with asymmetrical lateral flexion and/or axial rotation on the phantom, may exacerbate subclinical hindquarter pain. Nevertheless, the outcome of this study would benefit from an additional, objective clinical locomotor examination combined with analysis of motion during show jumping using modern IMU sensor technology.