Clinical and anatomical differences in varus and valgus deformities of chick limbs suggest different aetio‐pathogenesis

Abstract

SUMMARYLeg deformities were investigated in three flocks of broilers (n = 600, n = 817, n = 361). Two types of twisted legs were characterized: varus of the tarsal joint (1 to 3% of birds) and valgus of the tarsal joint (30 to 40% of birds) with mild, intermediate and severe valgus angulation. Varus angulation appeared suddenly, between 5 and 15 days of age, was unilateral in 80% of cases and affected mainly the right limb. Medial tendinous displacement was always present and led to severe locomotor handicap and, as a consequence, decreased 7-week body weights. In the right legs, a marked inward rotation of the femora, medial angulation of the tibiotarsi and metatarsi, and a shallow distal groove in the tibiotarsus were observed. By contrast, the load bearing limbs showed anteroposterior curvature of the tibiotarsus.Valgus angulation appeared progressively between 2 and 7 weeks of age and became severe in 5% of cases. This disorder was often bilateral. In 60% of birds affected with severe valgus, there was lateral displacement of the gastrocnemius tendon. Mild locomotor disturbance was observed in broilers with intermediate angulation, while severe valgus was associated with lameness, antero-posterior curvature of tibiotarsi and lateral deviations of metatarsi and in some birds a reduction in growth rate. Absence of other bone deformity in birds with mild and intermediate valgus suggests that valgus angulation does not originate from bone abnormalities. Clinical, epidemiological and anatomical differences between both types of angulations suggest that they may be of a different aetio-pathogenesis. Varus could originate from early displacement of the gastrocnemius tendon, which seemed secondary to leg deformation in birds affected with valgus angulation.

Identifying and monitoring pain in farm animals: a review

“…For example, after beak trimming, hens and turkeys gave fewer pecks (Gentle and Hunder, 1991). To avoid musculoskeletal pain, birds can limp or take relieving postures, ranging from a slight change in the positioning of the leg to a complete loss of support by the painful member (Kestin et al, 1992;Leterrier and Nys, 1992). Lame chickens spent more time lying and walked less (Weeks et al, 1997 and2000), and turkeys with musculoskeletal disorders were less generally active than controls (Duncan et al, 1991).…”

Sequential feeding with variations in energy and protein levels improves gait score in meat-type chickens

“…Time spent standing, eating and scratching did not differ between S1 and S2 birds when they were fed the same diet, only time spent exploring tended to be lower in S2 birds when fed the E1P2 diet. The clinical observations indicated that gait score was mainly impaired due to rotated tibias and varus-valgus angulations of the tarsal joint (Leterrier and Nys, 1992). Mean gait score improved in the sequential feeding groups (Table 4).…”

Genetic parameters of the twisted legs syndrome in broiler chickens

“…The latter is most often associated with a medial tendinous displacement. 'Unilateral' or 'bilateral' varus were further distinguished as suggested by Riddell (1983) and Leterrier and Nys (1992), but these data were pooled for the analysis. All animals were thus classified as healthy, valgus or varus.…”

“…McCullagh and Nelder (1989) (Leterrier and Nys, 1992;Riddell, 1992) (1985), and Albert and Chib (1993) (Johnson and Kotz, 1970). Assuming that y* is the largest amongst all the y * values, the probability of observing the ith category corresponds to:…”

“…Leg disorders have important economic consequences, such as a decrease of body weight (Hartmann and Flock, 1979;Leenstra et al, 1984; Leterrier and Nys, 1992), and culling of the most affected birds. Furthermore, as discussed by Sorensen (1989), decreasing leg disorders should contribute to improving animal welfare.…”