Effects of Varying Dietary Protein and Lipid Levels on Growth Performance and Hepatocyte Changes in Juvenile African Cichlids (Pseudotropheus socolofi and Haplochromis ahli)

Abstract

Abstract African cichlids are popular species produced commercially in South Florida for the aquarium trade. In their natural habitat, African cichlids show variations in feeding behavior, ranging from strict herbivory to omnivory to carnivory, and they are therefore excellent model species for nutrition work. The effects of varying dietary protein and lipid levels on the growth performance and hepatocyte changes of juvenile ornamental African cichlids were compared between Pseudotropheus socolofi, an omnivore, and Haplochromis ahli, a carnivore. It was hypothesized that the omnivore would have a lower protein requirement and show a higher incidence and severity of liver pathology when fed a high‐fat diet than the carnivore. Four diets were formulated using two crude protein (CP) levels (35–36% and 55–56% CP) and two lipid levels (8–10% and 19–20%), with resulting gross energy levels between 4000 and 5300 kcal/kg. P.socolofi (0.89 g, 4.1 cm) and H.ahli (2.1 g, 5.7 cm) were fed three times daily at 10% body weight per day (BW/d) for the first 3 wk, then 6% BW/d for the remaining 5 wks. Survival was greater than 86% for all treatments. Average weight gain of carnivorous H.ahli did not differ among the four diets and was greater than that of P.socolofi. P.socolofi grew larger when fed a high‐protein/high‐lipid diet compared to a high‐protein/low‐lipid diet or both the low‐protein diets. However, pathological changes to the liver were observed in P.socolofi fed a diet high in both protein and lipid. Carnivorous H.ahli tolerated higher levels of dietary lipid than the omnivorous P.socolofi. Both species showed significant growth, with no pathological changes occurring in the liver when they were fed a diet of 36% CP, 10% lipid, and 4000 kcal/kg gross energy.