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

A study was conducted to examine the effect of dietary cation-anion difference (CAD, Na⁺+K⁺-Cl^–, mEq kg ^–1) on acid-base balance, food consumption and growth of juvenile African catfish, Clarias gariepinus. Four dietary CAD levels (-100, 100, 500, 700 mEq kg^–1) were established by altering levels of NaHCO₃, CaCl₂ and NH₄Cl in the diets. The group fed the diet of excess anions (CAD: -100 mEq kg^–1) had low food consumption and growth rate. Food consumption and growth increased linearly with an increase in dietary CAD within the range -100 to 700 meq. kg^–1. 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 food intake and growth performance of C. gariepinus at higher CAD levels may be related to a reduced maintenance costs for homeostasis.