The nutritional value of poor proteins fed at high levels

The same six high-protein diets that were fed to rats (Carpenter & Anantharaman, 1968) have now been fed to chicks. 2. The net nitrogen retention by chicks, per 100 kcal consumed, was for each diet greater by 20–50% than the retention by rats. For a diet based on a mixture of commercial protein concentrates the NDpCal % was 19·1 (± 0·18); this value greatly exceeded the theoretical maximum of 14·6 obtained from the equations of Miller & Payne (1963). 3. Although groundnut protein plus lysine has a calculated chemical score of only 56, chicks receiving this at a high level retained N at the same rate (NDpCal % of 17·5–17·9) as those receiving a diet which included egg protein at the level (26% of the dietary ME) predicted to be optimal for them. 4. The ‘endogenous + metabolic’ losses of N were in almost the same proportion to metabolic size for chicks as for rats.