Godfrey Kubiriza

Makerere University

Godfrey is a Lecturer at the Department of Zoology, Entomology and Fisheries Sciences, Makerere University, Uganda. He was a UNU-FTP fellow in 2009/2010 and specialized in sustainable aquaculture management at Holar University College, Iceland. He has completed his PhD thesis (pending defense) in aquaculture fish nutrition at the University of Iceland. Godfrey has published paper in reputable journals on several aquaculture aspects including on the effects of lipid oxidation on farmed fish, alternative protein sources in East Africa, and on the implementation of cage culture on Lake Victoria among others. In addition to teaching, Godfrey is an active researcher and extension agent with special interest aquaculture fish nutrition and seafood safety.

SESSIONS:

Opportunities in aquaculture, Mon 15:20

Rosemary oil promotes growth and antioxidant enzyme activity of juvenile Arctic charr compared to ethoxyquin and bladderwrack powder

ABSTRACT

Continued use of synthetic antioxidants such as Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA) and Ethoxyquin (EQ) in fish feeds has raised concerns related to animal welfare and food safety. The aromatic amine EQ (1, 2-dihydro-6-ethoxy-2, 2, 4-trimethyl quinoline) is commonly used in aquafeeds, but its continued use has raised concerns related to animal welfare and food safety. Concerns have been raised about the potential carcinogenic effects that could arise among humans consuming fish contaminated with EQ. Therefore, there is interest to search for alternative antioxidants with minimal adverse effects not only on the consuming fish and humans, but also on aquafeed colour, flavour and odour. This study examined the relative efficacy of the natural antioxidants rosemary oil (RM) and powdered Bladder wrack (BW), a sea weed from the coastal waters of Iceland to the synthetic Ethoxyquin (EQ) in stabilizing lipid oxidation in herring oil. The effects of these antioxidants on the growth and antioxidant enzyme activity were studied in Arctic charr. Lipid oxidation stability was monitored by assaying free fatty acids (FFA), peroxide value (POV) and anisidine value (AnV) of herring oil treated with either RM or BW or EQ at five concentrations (i.e., 100, 200, 300, 400, 500 ppm EQ equivalent). Growth and antioxidant enzymes activity (for Catalase, CAT; Glutathione peroxidise, GPx and Superoxide dismutase, SOD) were studied in Arctic charr fed diets containing RM or BW or EQ at 100, 300 and 500 ppm EQ equivalent, respectively. To a reasonable extent, both RM and BW stabilized lipid oxidation in herring fish oils, although RM was more effective than BW. At elevated concentrations, the efficacy of RM was very close to that of the synthetic EQ. Growth was significantly affected by antioxidant types and concentration level, being fastest in fish fed a diet without antioxidants, followed by the group fed RM-treated diets. Slowest growth was in the fish groups fed diets treated with EQ and BW. CAT, GPx and SOD activities increased with dietary concentration of RM, but not with BW and EQ. These results suggest that RM can be used at elevated concentrations to stabilize lipid oxidation in aquafeeds instead of EQ. Additionally; RM can