Influence of Dietary Phosphorus Levels on Growth and Mineral Availability in Rainbow Trout

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∼29.7 mg/g). Growth, PER and NPU were not influenced by the dietary P at the level of 19.7 mg/g, but were decreased by 25.1 mg P/g or more. P, zinc (Zn) and manganese (Mn) contents in vertebrae were significantly lowered by the diet containing P of more than 25.1 mg/g. Zn absorption was significantly influenced by the excess amount of dietary P, namely it was lowered by P at levels exceeding 19.7 mg/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 and reduced Zn and Mn in the body of rainbow trout. It is suggested that the available P content in rainbow trout diet might be regulated to be less than 15 mg/g.