Over the past several decades, the poultry industry has used selective breeding to double the average market weight of chickens raised for meat while cutting nearly in half the amount of time it takes for birds to reach market weight. Researchers at the University of Guelph in Ontario, Canada, recently released a groundbreaking multidisciplinary study that examines how this practice of accelerated growth affects the health and welfare of chickens.
This new research—partially funded by the nonprofit organization Global Animal Partnership (G.A.P.)—assessed the health and welfare of 7,500 chickens of 16 different genetic strains, using indicators such as behavior, physiology, and anatomy, among others. According to the study’s summary, chickens with fast growth rates and high breast yields suffer from poor welfare outcomes, including “lower activity levels, poorer indicators of mobility, poorer foot and hock health, higher biochemical markers of muscle damage, higher rates of muscle myopathies, and potentially inadequate organ development.” A working group of experts will use the results of the study to determine which chicken breeds will be allowed under G.A.P.’s welfare-rating program, with potential to impact the lives of up to 300 million chickens annually raised for meat in accordance with the program’s standards.