The Effects of Oxidized Fish Oil on Growth Performance, Body Composition, and Intestine Histology of Nile Tilapia ( Oreochromis niloticus ) Fingerlings

Fish oil is a major source of energy and essential fatty acids for farmed fish; however, it is highly susceptible to oxidation during storage. This study aimed to evaluate the effects of oxidized anchovy oil on growth performance, body composition, and intestinal histology of Nile tilapia ( Oreochromis niloticus ) fingerlings. Juvenile fish with an initial mean body weight of 15.07 ± 0.58 g were randomly stocked into nine fiberglass tanks, with three dietary treatment groups and a stocking density of 50 fish per tank. Experimental diets were prepared using fish oil with varying peroxide values: fresh oil (4.95 meq/kg) for the control group, and oxidized oil (50 and 100 meq/kg) for the second and third treatment groups, respectively. All diets were formulated to be isoproteic (35% crude protein) and isolipidic (8% crude lipid), and fish were fed at 3% of body biomass. Results indicated that fish fed with fresh anchovy oil exhibited significantly higher growth rates, increased body protein and unsaturated fatty acid content, and normal intestinal morphology compared to fish fed oxidized oil. In conclusion, the inclusion of oxidized fish oil negatively impacted growth performance, body composition, and gut histology in O. niloticus fingerlings.