Genetic selection of broilers and welfare consequences: a review

The genetic selection of broilers over the past 60 years has focused narrowly and intensely on production traits, namely growth rate and feed efficiency. This has led to significant welfare problems in birds grown for meat, including leg disorders, cardiovascular diseases, and resulting high mortality rates, while the breeder birds are subjected to severe feed restriction. Bone problems such as bacterial chondronecrosis and tibia dyschondroplasia are prevalent, and recent studies have reported the prevalence of birds with moderate to severe gait impairment to be between 5.5 and 48.8%. Worldwide, over 66 billion broilers are slaughtered annually. This huge scale of meat chicken production means that welfare problems are widespread and are likely to increase in severity due to the increasing global human population, increasing demand for meat, and a continued focus on efficiency of production in the agricultural sector. The commercial broiler industry therefore represents some of the most serious animal welfare issues in agriculture. There is an urgent need to address these problems by making welfare traits high priorities in breeding programmes and integrating these with other breeding goals. Many studies recommend the use of slower-growing breeds that do not have the same welfare problems. Addressing these welfare issues is essential to improve bird welfare and for social acceptability and sustainability of the broiler industry worldwide.