The influence of dietary cation-anion differences on acid-base balance, food intake, growth and nutrient utilisation of juvenile African catfish Clarias gariepinus (Burchell)

摘要

A 5-week study was conducted to examine the effect of dietary cation-anion difference (CAD, Na++K+-Cl-, mEq/kg) on acid-base balance, feed intake and growth of juvenile African catfish, C. gariepinus. Four dietary CAD levels (-100, 100, 500, 700 mEq/kg) were established by altering levels of NaHCO3, CaCl2 and NH4Cl in the diets. 55 fish, 36.4 g, were distributed to each of 12 aquaria (70 litres). The group fed the diet of excess anions (CAD: -100 mEq/kg) had low feed intake and growth rate. Feed intake and growth increased linearly with an increase in dietary CAD within the range -100 to 700 mEq/kg. Blood pH was not significantly influenced by dietary CAD. A quadratic relationship between Na+, Cl- and CAD level in plasma and dietary CAD was found.Body composition of fish and nitrogen/energy utilisation efficiency differed between dietary CAD treatments. The results suggest that dietary CAD influence acid-base regulation and thus the energy costs for maintaining homeostasis. The increased feed intake and growth performance of C. gariepinus at higher CAD levels may be related to a reduced maintenance costs for homeostasis.