Assessing the waddle: An evaluation of a 3-point gait score system for ducks

Impaired walking ability is an economically important welfare problem that affects poultry raised for meat production, including Pekin ducks. To gain a better understanding of the impacts of walking impairments on duck production, and to identify contributing variables and plausible remedies, an accurate measure of walking ability must first be defined. The viability of a 3-point gait score system for characterizing the walking abilities of Pekin ducks was evaluated. Specifically, we examined whether the qualitative gait score categories corresponded to quantitative gait parameter measures, and evaluated the inter- and intra-rater reliabilities of the gait score system. Commercial Pekin ducks aged 13 to 14 d (14 d; 248 ducks), 20 to 21 d (21 d; 350 ducks), and 30 to 32 d (31 d; 368 ducks), were video recorded and gait scored using a 3-point system (GS0 = best gait; GS2 = poor gait) as they crossed a Tekscan(®) gait analysis system. Gait structure parameters were calculated based on 4 steps made by each duck. The most prominent differences were observed at 21 d and 31 d of age between the ducks with GS0 and GS2, with GS2 scoring ducks walking a shorter total distance, having greater differences in the amount of pressure applied to the right versus left leg, and the amount of time spent standing on 2 feet between steps. Gait score reliabilities were calculated separately for observers who received minimal training (M, N = 10) and those who viewed and discussed the sample cases (V, N = 13). Both groups assessed the gait of ducks from video footage. Inter-rater reliability (Fleiss kappa) was lowest for 14 d old ducks (M: k = 0.47, T: k = 0.62), and best for the 32 d old ducks (V: k = 0.75; T: k = 0.8). Overall, intra-rater reliabilities (Pearson's correlation) were high and were unaffected by the scorer's level of training (M: r = 0.87; V: r = 0.87; t21 = 0.43). The results indicate that a 3-point gait score system is a promising tool for assessing the walking ability of ducks at 21 d of age and older.