In order to clarify the requirements of dietary minerals, i. e., calcium, phosphorus, potassium, magnesium, iron, and trace metals, by the prawn, Penaeus japonicus, the effect of these minerals on the growth and the feed efficiency was examined with a purified diet.
The supplements of calcium, magnesium, and iron did not improve the nutritive value of the diet at levels of 2%, 0.3%, and 0.02%, respectively. The supplement of iron rather reduced the value. The improved effect of phosphorus supplementation was noticed at a 2% level in the diet, and this was more pronouced in the absence of calcium. The group fed on the diet supplemented with potassium at a level of 1% showed higher growth and feed efficiency than those of the group fed on the diet without it. The suitable level of trace metals supplemented in the diet was found to be 0.2%, while levels over 0.2% resulted in a lower nutritive value than the diet without the supplement.
From these findings, it appears that 2% of phosphorus, 1% of potassium, and 0.2 % of trace metals should be supplemented into the purified diet for favorable growth of the prawn, while calcium, magnesium, and iron supplements are dispensable.