[The protein turnover of different leghorn hybrids]

After N-balance experiments with leghorn-hens of five different genetic origins in the top laying period, the advanced laying period as well as at the end of the laying period and with feeding of soybean meal/fish meal protein, the nitrogen maintenance requirement per live weight kg0.67 was ascertained regressively by approximation of the N-balance from N-increasing experiments to an exponential function. The Net Protein Utilization (PNu) curve and the apparent Net Protein Utilization (PEW) curve could be described as utilisation values from the N-retention curve (e-function). Moreover the relation between N-intake/LW kg0.67 and egg-N-discharge/LW kg0.67 from N-balance made it possible to estimate N-retention in the body. Finally, capability of the five origins at equal protein and S-AA intake respectively were compared.