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Effect of lameness on hock angles of replacement gilts
The objective of this study was to investigate whether hock angles differ significantly between lame and sound legs in replacement gilts. Thirteen lame gilts on the rear right leg were moved to a pen where digital images (i.e. still pictures) were recorded while the gilt walked to capture images of the leg flexing forward and backward on both profile views. Standing images were also captured. On average, 9 high quality images were used for analysis per gilt. Hock angles were measured for both lame, and sound rear legs. Angles were measured by tracing the front and back of the joint between the fibula/tibia and tarsals, with the anterior and posterior positions acting as the anchor. Flank to flank measurement was recorded to estimate body weight. Data were analyzed using mixed model methods with leg (sound or lame), leg position (forward, standing, or backward), and their interaction included as fixed effects. Estimated BW was included as a linear covariate. Gilt was included as a random effect. Hock angle varied between the sound and lame leg. When accounting for the average angle of all three positions, lame legs had wider hock angles when compared with the sound leg (141.1 vs 136.9 ± 1.9 degrees, respectively; P < 0.05). Hock angles did not differ between lame and sound legs when the leg was positioned forward (P > 0.05). However, while standing and while flexing legs backwards, hock angles were greater on the lame leg when compared with the sound leg (136.7 vs. 132.7 ± 2.1 degrees and 145.4 vs. 136.1 ± 2.1, respectively; P < 0.05). Body weight was not a significant source of variation for any traits evaluated (P > 0.05). Straighter hock angles on the lame leg could indicate an effort of the gilt to balance her body while moving due to the discomfort she might be experiencing in the lame leg.
Keywords: Replacement gilts, lameness, hock angle