Hip dysplasia in rabbits: association with nest box flooring.

ABSTRACT

PURPOSE: To study etiologic aspects of hip dysplasia in a colony of Dutch-belted rabbits. METHODS: Rabbits used in the study were part of a reproductive toxicologic study. Incidence of hip dysplasia among 296 Dutch-Belted rabbit kits raised on waxed cardboard, smooth Plexiglas, or Plexiglas covered with textured adhesive strips was recorded. All animals were examined at 2 to 4 weeks of age for inability to adduct one or more limbs, then were classified as normal or dysplastic. A subset of 16 juvenile male rabbits (4 normal, 12 affected) raised on Plexiglas flooring were given a physical examination at 12 weeks of age followed by complete necropsy. In four animals (one normal, three affected), pelvic radiography and neurologic examination were performed. RESULTS: Seven percent of the rabbits kits reared on waxed cardboard flooring and 22% of those reared on smooth Plexiglas flooring developed hip dysplasia. Animals reared on Plexiglas floor with traction strips did not have evidence of hip dysplasia. Among the animals selected for detailed analysis, body weight was similar between rabbits with or without splay leg. Affected animals had splaying of one or both hind limbs, various degrees of flattening and reduction of the size of the femoral head, subluxation of the hip, valgus deformity, and patellar luxation. Histologically, there was marked thickening of the hip joint capsule with fibrocartilage formation, mild trabecular bone loss, and bony sclerosis of the proximal portion of the femur and adductor muscle hypoplasia. CONCLUSIONS: Provision of non-slippery flooring during the postnatal period is critical in preventing development of hip dysplasia in rabbits. Hip dysplasia resulted in significant musculoskeletal changes, but not abnormal neurologic development.