Males are generally heavier and have thicker shanks than females.
Therefore, we tested the hypothesis that, because the leg gaps of shackles are fixed in size, male broilers would struggle more than females. Upon shackling, the latencies to struggle, numbers of struggling bouts, and total time spent struggling were recorded during a 1-min test period. However, there were no detectable correlations within sex. Body weight was not significantly correlated with any of the struggling behavior measures. Although other gender-related factors may be influential, an interpretation of our findings based on sex differences in CRS seems the most parsimonious.