Abstract
Feeding experiment was conducted to determine the influence of dietary phosphorus levels on growth and mineral availability to juvenile rainbow trout. Mono-basic potassium phosphate was supplemented to semipurified diet at 2, 4, 6, and 8%, in order to obtain graded dietary phosphorus (P) levels (11.7_??_29.7mg/g). Growth, PER and NPU were not influenced by the dietary P at the level of 19.7mg/g, butwere decreased by 25.1mg P/g or more. P, zinc (Zn) and manganese (Mn) contents in vertebrae were significantly lowered by the diet containing P of more than 25.1mg/g. Zn absorption was significantly influenced by the excess amount of dietary P, namely it was lowered by P at levels exceeding 19.7mg/g diet.
The study demonstrated that excess amounts of dietary P at a level three times higher than the P requirement lowered protein utilization and Zn absorption, induced poor growth andreduced Zn and Mn in the body of rainbow trout. It is suggested that the available P content inrainbow trout diet might be regulated to be less than 15mg/g.
