Reduction of dietary protein in broiler diets not only reduces n-emissions but is also accompanied by several further benefits

SUMMARY In the light of recently revised German legislation on on-farm nitrogen (N) management, the impact of decreasing dietary N-load at balanced dietary amino acid supply on growth performance and N-excretions was examined in 5000 mixed-sex Ross 308 broilers from 1 to 40 d of age (20 floor pens with 250 birds each). In addition to diets representing the German standard with 22.0, 20.6, 20.0, and 19.5% crude protein (CP) in starter (1–10 d), grower I (11–16 d), grower II (17–30 d), and finisher feed (31–40 d), a N-reduced German standard (21.0%, 20.0%, 19.6%, and 18.9% CP) was fed in treatment 2. Dietary CP was further reduced in treatment 3 (21.0%, 19.5%, 18.7%, and 18.0% CP) and treatment 4 (21.0%, 19.0%, 18.0%, and 17.0% CP). Growth performance, feed conversion (FCR), carcass quality, N-utilization and litter quantity (at termination) were examined. Final body weight were similar between treatments 1, 2, and 3 but slightly impaired in treatment 4 (P 0.05). Dietary N-reduction resulted in gradually improved N-utilization (P