AbstractsBiology & Animal Science

Introduction It is often claimed that stallions used for both breeding and showjumping perform less well in competitions during the breeding season. The demands on the back and pelvis during semen collection may impair the range of movement required for showjumping. Therefore, the aim of this study was to assess the biomechanics of the stallion’s hindquarters by examining the range of motion (ROM) of the hindquarters, in particular the pelvic flexion, during both the mounting and ejaculatory phases of semen collection. Materials and methods The kinematics of the hindquarters of six sportshorse stallions regularly used for semen collection were studied at the mounting and ejaculation phases during semen collection on a phantom. Green spherical skin markers were placed on Th5, tuber coxae, proximal femur and tibia, and distal tibia and metatarsus. At each phase a total of 6 angles between the skin markers was measured using a home-video camera positioned perpendicular to the phantom. The differences in joint angles between these two phases were statistically compared using commercially available software (SPSS) at a significance level of P<0.05. Results Horses showed a significantly larger variation in joint angle values during the mounting than during the ejaculation phase. They also showed more extension in the tarsal than in the hip and stifle joints; there was also more extension in the stifle than in the hip joint (P<0.05). The pelvic flexion angle was significantly larger with more extension than the tarsal joint angle (P<0.05). The position of the hindlimb in relation to the ground was significantly more upright than that of the body (P<0.05). Conclusions During the mounting phase the pelvis shows a larger joint angle range than during the ejaculation phase. During both phases the tarsal joint shows more extension than the hip and stifles joints, the stifle shows more extension than the hip, and the pelvis shows more extension than the tarsal joint. Meanwhile, the hindlimb is in a significantly more upright position than the body. The extreme flexion and extension of the pelvis may impose a very different loading on the musculoskeletal structures, especially when during mounting also asymmetric lateroflexion and/or axial rotation are involved, possibly provoking locomotor pain in the hindquarters. Still, it remains somewhat unclear how exactly this will interfere with the ability to extend the pelvis during showjumping.