Effects of dietary tricalcium phosphate on the growth and mineral availability in Japanese flounder

A 10-week feeding trial was conducted to investigate the effects of dietary tricalcium phosphate(TCP) on growth and mineral availability in juvenile J apanese flounder (Paralichthys olivaceus). A 0.25% Ca supplement from Ca-la ctate to the diet (diet 2) significantly increased the growth of fish compa red to the basal diet 1 without a Ca supplement. However, a dietary supplem ent of 2.5% Ca from TCP (diet 3) did not improve the growth and decreased Z n and Mn contents of bone when compared to the basal diet 1. A 0.25% Ca sup plement from Ca-lactate to the diet (diet 4), in addition to the 2.5% Ca su pplement from TCP, also could not improve the growth and Zn and Mn contents of bone. A Zn supplement to the diet (diet 5), in addition to the 2.5% Ca supplement from TCP, increased the Zn content of bone but did not improve t he growth. The present study suggests that dietary TCP introduces decreased growth and low availability of Zn and Mn in Japanese flounder and that eas ily digestible Ca supplementation to the TCP-riched diet alone can not impr ove the growth and mineral availability. In a TCP-riched diet (fish meal di et, for example), both easily digestible Ca and higher amounts of Zn and Mn supplements may be necessary for obtaining improved growth and mineral ava ilability in juvenile Japanese flounder.