Factors Affecting Flock Uniformity in Broiler Production: Individual, Environmental, and Management Characteristics.

Flock uniformity is a critical factor influencing productivity, production efficiency, animal welfare, and overall economic outcomes in broiler production. Despite its importance, uniformity is often overlooked in commercial settings, where production goals typically focus on maximizing average BW and overall flock performance rather than minimizing variation among individual birds. This review aims to summarize the diverse factors that affect flock uniformity in broilers. Under standard conditions between days 14 and 49, flock uniformity typically reaches approximately 90%. Both intrinsic factors, such as genetics, initial BW, age, sex, and rearing method, and extrinsic factors, including housing, management, and vaccination practices, have been shown to influence uniformity. Environmental and management challenges, such as heat stress, nutrient deficiencies, microbial infections, high stocking density, feed form, and mixed-sex rearing, can further reduce uniformity by 2.5-15%. These findings highlight the high sensitivity of flock uniformity to multiple stressors, which may interact rather than act independently. Moreover, these findings highlight the need to consider both baseline and challenging factors in broiler production and support the development of targeted management and environmental strategies to improve flock uniformity and enhance overall production efficiency.