Effects of total replacement of fish oil on growth performance, lipid metabolism and antioxidant capacity in tilapia (Oreochromis niloticus)

Five iso-nitrogenous (crude protein 32 %) and iso-energetic (gross energy 15 MJ kg−1) practical diets were formulated by totally replacing fish oil (FO) with soybean oil (SO), rapeseed oil (RO), linseed oil (LO) and pork lard (PL), respectively. These diets were fed to triplicate groups of 30 gift tilapia (Oreochromis niloticus) (mean initial weight 9 g). Fish were fed three times a day for 8 weeks at 26.5 ± 2.5 °C. The results showed that the replacement of FO with RO or LO or PL in tilapia diets did not affect growth or feed utilization. Fish fed SO exhibited lower specific growth rate and protein efficiency ratio, and higher feed conversion ratio. The lowest hepatosomatic index, hepatopancreas lipid content, hepatopancreas malondialdehyde contents, lipoprotein lipase and malate dehydrogenase activities in liver were observed in fish fed FO, LO and RO. Fish fed FO or LO exhibited higher aspartate transaminase and alanine transaminase activities in liver and higher total antioxidant capacity, superoxide dismutase and alkaline phosphatase activities in serum, but the values of these parameters were lower in fish fed PL in comparison with the other groups. This study showed that alternative lipid sources could be used successfully in tilapia diets except for SO. Total replacement of dietary fish oil by linseed oil could be possible without adverse effects on fish health.