Potassium requirement of fingerling channel catfish, Ictalurus puntatus

Abstract

An 8-week feeding study was conducted to determine the potassium requirement of juvenile channel catfish. Six dietary levels of potassium ranging from 0.01 to 0.49% were fed to triplicate groups of catfish (initial average weight of 16.6 g) in flow-through aquaria at a water temperature of 26.7 ± 1.1 °C. The rearing water contained 4 mg/l potassium. No significant differences were observed in either weight gain or feed efficiency among the experimental groups. No dose-response relationship was apparent between dietary potassium level and whole body potassium concentration, indicating that these animals do not have a dietary requirement for potassium with potassium in the rearing water at a concentration of 4 mg/l or higher. However, when these data were used to calculate the whole body potassium balance for each group of fish it became clear that the fish do have a potassium requirement that can be met by either dietary potassium or the uptake of potassium from the rearing water. Linear regression analysis of the dietary potassium levels vs. whole body potassium balance values indicated a potassium requirement value of 0.26%. This requirement value is similar to the dietary potassium requirement of the rat, chick and young pig.