Introduction: World production of citrus fruits exceeds 124.3 million tons annually. Citrus peels make up about 60–65 % of the citrus fruit body weight, which means that 74.6-80.8 MT of peels may be available annually as animal feeds. Citrus peels are rich sources of functional bioactive compounds, especially phenolic (flavonoids and phenolic acids) and essential phytochemicals that possess health benefits. Therefore, this study investigated the effect of replacement of maize with citrus peels from sweet oranges fermented with Penicillium notatum on the growth, carcass quality and biochemical profile of African catfish.
Materials and methods: Orange fruits were harvested, washed in clean waters and the peels removed, dried at room temperature and blended into fine particles. The particles were fermented for 7 days using Penicillium notatum. The fermented citrus peel was used to replace 0, 25, 50, 75, and 100% of maize in the diets of Clarias gariepinus juveniles (12.50±14g) and the fish were fed in triplicate groups to apparent satiation twice daily for 56 days.
Results: Table 1 shows that fermentation improved the nutritional quality of the citrus peels, which helped to improve fish performance and nutrient utilization. The fermented peels have protein of 26.2% which is more than double the protein of 10% contained in maize.
Growth performance, Table 2, shows that the fermented peels could replace up to 75% of maize in the diets of the fish. Wt. gain and SGR were statistically the same in the fish fed diets with up to 75% of citrus peels. Peels also increased (P<0.05) carcass ash and protein.
Biochemical profile indicates that total cholesterol, triglycerides, LDL, urea and MDA decreased marginally while HDL increased marginally with increasing levels of peels in the diets.
Conclusion: Replacing maize with fermented citrus peels positively influenced growth, carcass minerals and fish quality.