Abstract
ABSTRACTGenetic selection for increased growth rate and muscle mass in broiler chickens has been accompanied by mobility issues and poor gait. There are concerns that the Pekin duck, which is on a similar selection trajectory (for production traits) to the broiler chicken, may encounter gait problems in the future. In order to understand how gait has been altered by selection, the walking ability of divergent lines of high- and low-growth chickens and ducks was objectively measured using a pressure platform, which recorded various components of their gait. In both species, lines which had been selected for large breast muscle mass moved at a slower velocity and with a greater step width than their lighter conspecifics. These high-growth lines also spent more time supported by two feet in order to improve balance when compared with their lighter, low-growth conspecifics. We demonstrate that chicken and duck lines which have been subjected to intense selection for high growth rates and meat yields have adapted their gait in similar ways. A greater understanding of which components of gait have been altered in selected lines with impaired walking ability may lead to more effective breeding strategies to improve gait in poultry.
Highlights
Intense selection for production traits in poultry over approximately 60 generations has led to considerable genetic gain
The lines unselected for high muscle mass both walked with a significantly narrower step width than their heavier conspecifics (P
There was a line by age interaction in Experiment 1 (P=0.021); step width increased substantially after five weeks in both chicken lines whereas no substantial increase in step width was observed after five weeks in the Pekin commercial hybrid (Fig. 2A)
Summary
Intense selection for production traits in poultry over approximately 60 generations has led to considerable genetic gain. During this period the body mass of the meat type (broiler) chicken has increased by 300% (Knowles et al, 2008). Estimates of the prevalence of gait problems in broiler chickens have been reported between 15% and 30% (Kestin et al, 1992; Sanotra et al, 2001, 2003; Knowles et al, 2008). The true prevalence of gait problems is difficult to obtain, because of variation between studies in the strains of birds assessed, the gait scoring systems used, the age at which birds are assessed and the
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