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In a protein reduction feeding trial (Study 1) on a commercial broiler farm in northern Germany, it was attempted to be shown that research results from station tests on protein reduction can be transferred to agricultural practice. In a second study, the limits of the N reduction were tested in a research facility. In Study 1, commercial standard feeds were fed to the control group (variant 1:210,000 animals; n = 5 barns). In the test group (variant 2:210,000 animals; n = 5 barns), the weighted mean crude protein (CP) content was moderately reduced by 0.3%. The nitrogen reduction in the feed did not affect performance (feed intake (FA), daily gain (DG), feed conversion (FCR)), but nitrogen conversion rate increased from approx. 61% to approx. 63%. The solid litter weight was reduced by 12% and nitrogen excretion by 9% (p < 0.05). Significantly healthier footpads were due to lower water intake (−4%; p < 0.05) and a numerically drier bedding. In Study 2, responses of treatments (1250 broiler per variant; n = 5) showed that sharper N-lowering (−1.5% CP; weighted average) did not impair performance either, but N-conversion improved and N-excretions decreased significantly. Converted to a protein reduction of one percentage point, the N excretions were able to be reduced by 22% in Study 1 and 18% in Study 2. Feeding trials in the commercial sector, such as the present Study 1, should convince feed mills and farmers to allow the latest scientific results to be used directly and comprehensively in commercial ration design. [ABSTRACT FROM AUTHOR]