The effect of morphology on walking ability in the modern broiler: a gait analysis study
This study tests the hypothesis that growth rate and bodyweight affect walking ability in broilers by comparing objective measurements of the spatial and temporal gait parameters of several groups of birds. Two strains of birds were used (relaxed and selected), raised on two feeding
regimes (ad-libitum and restricted), and culled at the same final bodyweight (commercial cull weight of 2.4 kg). The ad-libitum-fed selected birds walked more slowly, with lower cadences, and took shorter steps. The steps were wider, and the toes were pointed outwards, resulting
in a wider walking base. They kept their feet in contact with the ground for longer periods, having longer percentage stance times, shorter percentage swing times and increased double-contact times compared to the relaxed birds. These changes serve to increase stability during walking and
are a likely consequence of the morphological changes in the selected broiler - in particular, the rapid growth of breast muscle moving the centre of gravity forward, and the relatively short legs compared to their bodyweight (see Corr et aI, pp145-157, this issue). This altered gait would
be very inefficient and would rapidly tire the birds, and could help to explain the low level of activity seen in the modern broiler.