Spread bow leg syndrome in ostrich (Struthio camelus) chicks aged 2 to 12 weeks.

1. The incidence of spread bow leg syndrome and associated pathology in 15 ostrich chicks aged 2, 4, 8 and 12 weeks is reported. Measurements were made of hind limbs: femur plus tibiotarsus; tarsometatarus; phalanx I, digit III; phalanx II, digit III plus phalanx III, digit III; and phalanx IV, digit III. 2. A run was constructed (6 m x 1.7 m) and subdivided into 2 m sections and the time taken to traverse it was recorded. Measurements (cm) were made of the left and right footprints; the number of footprints and average stride length in 0 to 2, 3 to 4 and 5 to 6 m. Speed was calculated using distance run (m) divided by time taken (s). 3. The number of steps was greater in bow leg chicks aged 4 and 8 weeks by comparison with healthy birds. Stride length, however, was smaller in all age groups with bow leg. All speeds in bow leg chicks were lower than those in healthy birds, except for that recorded at 2 m in chicks aged 2 weeks which did not differ markedly. 4. In affected birds, feathers were sparse. Icterus was present. The tarsometatarsus was twisted, with severely inflamed joints, eroded distal ends, thickening of the cartilage and the presence of fibrous material surrounding the ligaments. Muscles in the hind limb were emaciated. 5. The syndrome compromises the ability of chicks to keep up with adults in flocks, and may compromise their ability to escape predation.