Modelling nitrogen use efficiency by world poultry production systems in 2050

Poultry production is highly efficient in terms of nitrogen retrieval among livestock species. Nevertheless, more than 60% of nitrogen feed to animals is lost, mostly as manure. The evolution of these production systems in future is uncertain and will be strongly affected by global economic and food systems development. A model describing poultry production systems, resources consumption and production efficiencies has been developed. A strong effect of socioeconomic pathways has been found. According to the results obtained, poultry production in future will be only sustainable under a paradigm of moderate meat and eggs demand and improving nutrient recycling.

Poultry production is one of the most animal agriculture efficient systems leading to a high protein recovery rate (Mottet et al., 2017). This high efficiency, as well as the ability of poultry to recycle by-products and food waste into cheap and high-value protein sources for humans (Truong et al., 2019), has led to a continuos increase of poultry production worldwide (poultry population increased almost 4-fold in the last 50 years acording to FAO, 2019), that is expected to continue in future (Alexandratos and Bruinsma, 2012). Nevertheless, the average recovery rate for protein on these animales ranges between 10 and 30% (Motet et al., 2017). The residual nitrogen from the poultry production system is mostly found on manure, that can be a source of pollution. More than 90% of poultry are chickens, providing more than 4.5 Gg of Nitrogen as feed in 2017 (FAO, 2019), mainly as chicken meat (c. 70%). Production systems are highly variable with different management, performances and which, in turn, affect local and global demand of resources as well as the N use efficiency. With the growing share in total population and animal products demand, poultry production will therefore play an important role in the global agro-food system during the next decades, as a food resource, feed consumer and manure producer.