Nutrition for juvenile African cichlids: The effects of varying dietary protein and energy levels on growth performance and liver condition

The objectives of this dissertation were (1) to determine the minimum requirements for protein and energy for juvenile African cichlids needed to provide normal growth without pathological changes in liver cells; and (2) to formulate a cost-effective model diet. A 12-week feeding trial was conducted to evaluate growth performance and hepatocyte changes of juvenile African cichlids (Pseudotropheus socolofi and Haplochromis ahli) fed commercial diets used on cichlid farms in South Florida. Growth was significantly greater (P < 0.05) for both species fed a trout starter pellet (52% crude protein, 17% lipid) than for fish on a mixed flake feed (45% crude protein, 7% lipid). This trial showed that the trout starter pellet may be suitable for commercial production of juvenile African cichlids up to 12 weeks of age; but prolonged feeding may result in excess lipid deposition and necrosis of the liver.; A 10-week trial was conducted to observe the effects of varying protein levels on growth performance and changes in hepatocytes of juvenile P. socolofi (0.09 g; 1.8 cm). Six diets were formulated with protein levels ranging from 32.5 to 58.8%. Survival was greater than 95% for all treatments. The minimum range of dietary protein to produce optimum growth of P. socolofi without significant changes in liver lipid levels or pathology was determined to be 36.9 to 42.5%.; A third feeding trial was conducted for 8 weeks to observe the effects of varying energy (ranging from 4,000 to 5,300 kcal/kg) at two protein levels (36 and 50%) on growth performance and hepatocyte change of P. socolofi (0.89 g; 4.1 cm) and H. ahli (2.04 g; 5.65 cm). Based on growth performance and liver condition, a diet containing 36% protein, 9.5% lipid at an energy level of 4000 kcal/kg, was determined to be suitable for commercial production of these juvenile African cichlids. With these requirements, the formulation of a practical diet became possible. This diet should improve nutrient use, provide growth rates equivalent to or better than growth rates of commercial feeds currently in use, decrease the level of liver and carcass fat deposition, and maintain good water quality.