Metabolic costs of changing the cation–anion difference in the diet of juvenile African catfish Clarias gariepinus (Burchell) |
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| Authors: | Dersjant-Li Verreth Tijssen Booms Verstegen & Huisman |
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| Institution: | Fish Culture and Fisheries Group, Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands; Animal Nutrition Group, Department of Animal Sciences, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands |
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| Abstract: | The influence of dietary cation–anion difference (CAD, Na+ + K+– Cl–, mEq kg–1) on energy metabolism and nitrogen losses in juvenile African catfish Clarias gariepinus (Burchell) was examined in fish exposed to different dietary CAD levels (–146, 116, 497, 713 and 828 mEq kg–1 diet). The experiment was conducted in open circuit balance respiration chambers over a 3-week period. Five 24-h monitoring periods were carried out at 3-day intervals during the experimental period with O2 consumption, ammonia and nitrate + nitrite (NOx) and CO2 production being measured at 5-min intervals for each chamber. The negative dietary CAD (–146 mEq kg–1) resulted in the highest energy expenditures (83 kJ kg–0.8· d–1). With increasing dietary CAD levels, heat loss gradually decreased to minimum values of 56 kJ kg–0.8 day–1 at a dietary CAD level of 713 mEq kg–1. Consequently, metabolizable energy utilization efficiency (MEU, percentage of retained energy over metabolizable energy) quadratically ( P < 0.05) increased and reached a maximum at a dietary CAD of 713 mEq kg–1. |
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| Keywords: | African catfish electrolyte balance heat production maintenance costs metabolic expenditures O2 consumption |
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