An evaluation of six dietary protein-to-energy (P/E) ratios was conducted to the early juvenile lobsters (Panulirus ornatus) by investigating the ratio effects on physiology, digestive enzyme activities, body composition, and amino acid profiles. Juvenile lobsters (0.25±0.01 g) were individually kept in aquaria and treated with six isoenergetic formulated diets of P/E ratios of 21.8, 22.5, 23.5, 24.6, 25.3 and 26.6 mg KJ−1. After 8 weeks of feeding experiment, the differentiation on dietary P/E ratios was found to have affected the specific growth rates, but not the survival, moult increment, moulting rate, moult interval and average daily moulting rate of juvenile lobsters. The dietary P/E ratio also influenced the protease, lipase, super oxidase dismutase activities, and body composition of juvenile lobster. The increase in dietary protein levels significantly affected the increase of the specific growth rate, while increased dietary lipid levels only affected the length increments. Both protein and lipid content were found in the whole body of the juveniles which reflected the treated dietary composition. Results indicated that a P/E ratio of 26.6 mg KJ−1 (55% dietary protein and 9% dietary lipids) can yield the maximum growth and digestive enzyme activities from among the studied diets.
