An evaluation of mineral supplementation of fish meal-based diets for African catfish

Abstract

Thirteen minerals have been demonstrated to be essential components of the diet of most terrestrial animals, and they may also be essential for fish (Davis and Gatlin 1991). However, unlike terrestrial animals, fish are able to absorb some minerals from their external aquatic environment, and this can complicate the determination of mineral requirements. Nevertheless, minerals are required for the maintenance of normal metabolic and physiological functions, and the lack of an essential mineral in fish diets may lead to several deficiency signs (NRC 1993; Watanabe et al. 1997). Consequently, aquafeed manufacturers usually supplement their feed formulations with mineral premixes. Fish meals contain high concentrations of minerals, including phosphorus in the form of bone ash. Additional phosphorus is usually added to fish diets but with growing concerns for the environmental effects of phosphorus discharge from aquaculture systems, research is being carried out to determine the minimum required amount of phosphorus supplementation (NRC 1993; Li et al. 1996; Eya and Lovell 1997). The need for dietary mineral supplementation for African catfish (Clarias gariepinus) fed practical diets containing high levels of fish meal has not been evaluated. The present study was conducted to evaluate the need for mineral supplementation, and also the suitability of two mineral supplements (a formulated mineral mix and a commercial Orykta TM mineral supplement) in practical diets for the African catfish.