1. The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. 2. In experiment 1 a high energy diet (HED, 14.8 kj ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. 3. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. 4. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. 5. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.
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