Abstract

The excessive intensive production of poultry meat and egg caused significant changes in poultry husbandry, behavior, and welfare. Therefore, animal welfare and behavior have become an important issue in poultry production and arises the necessity to reconsider all husbandry practices including group size and density. This review aims to investigate the association of group size with growth performance, detrimental behaviors, and welfare by reviewing current norms and regulations, as well as scientific literature in industrial poultry farms, including chicken, turkey, and quail. It has been found that group size can affect production performance, especially growth rates, feed efficiency, and number of competitors, which can lead to damaging behavior and consequently injuries in poultry. Due to the intensification of the poultry production systems, many natural behaviors of domesticated poultry, including food search strategies, hierarchy formation, and aggressiveness, are changed or modified, compared to their ancestors. Therefore, challenging behaviors in commercialized conditions and large groups of poultry must be investigated. The current recommendations and regulations of the industry for commercial poultry on group size and space requirements differ from scientifically investigated trials. On the other hand, available scientific research about the impact of flock size on poultry welfare, behavior, and production, has been carried out in experimental settings with flock sizes that are varied considerably from those used in the commercial settings. In conclusion, results from studies on optimum group size have indicated some degree of confounding and interactions between enclosure size and density. Furthermore, the social and physical environment can have a significant impact on a variety of welfare-related aspects and behavioral indicators. It is important to note that this evaluation focused on studies conducted in experimental settings, making it difficult to extrapolate the findings to commercial settings where thousands of birds are reared at once © 2022, Journal of World's Poultry Research.All Rights Reserved.