Gait parameters associated with GS1 versus GS0 or
GS2 were only detectable at older flock ages. At 21 d
old, GS1 ducks took an intermediate amount of time to
complete the 4 steps. On average, GS1 ducks traveled
an intermediate total distance as compared to ducks
with GS0 and GS2 scores at 21 d and 32 d of age. At
32 d of age, the difference in the amount of time ducks
spent on their left versus right foot as they propelled
themselves forward was intermediate for GS1 ducks as
compared to the GS0 and GS2 groups. A likely reason
why gait measures of 14 d old GS1 ducks did not
differ from those of GS0 and GS2 ducks is that mobility
issues became more common and/or pronounced as
the ducks aged, resulting in a more obvious separation
between the categories. Assessment of the incidence of
ducks within each gait score category was outside of
the scope of this study, but a decline in walking ability
has been associated with increased age in other poultry
species selected for fast growth. The walking abilities
of broiler chickens have, for example, been shown to
decrease between 17 and 38 d of age (Vestergaard and
Sanotra, 1999) and when measured at 28, 42, and 49 d
of age (Sørensen et al., 2000).