Effects of liquid and powdered fat on growth, health and muscle quality of juvenile GIFT Oreochromis niloticus

In the current production of aquafeeds, oils are usually added directly or by vacuum coating. However, few reports were seen about the application of fat powders in aquaculture. In this study, with soybean oil (SO, linoleic acid∶linolenic acid = 9∶1) and blend oil consisting of soybean oil and rapeseed oil (BO, linoleic acid∶linolenic acid = 5∶1) as dietary lipids, four formulated feeds (SOl, BOl, SOp and BOp) were prepared by adding SO or BO in liquid or powder forms. After the tilapia juveniles (GIFT Oreochromis niloticus) with an initial average weight of 15.38 g were fed with the diets in indoor aquarium for 8 weeks, the growth indexes including weight gain rate, specific growth rate, feed coefficient, hepatobody ratio and viscera ratio showed no significant difference among the four groups. However, compared with the corresponding indexes in fish fed SOl, the liver catalase and superoxide dismutase activity were significantly increased, while the muscle crude ash content was significantly decreased in fish fed SOp; the serum levels of triglyceride and low density lipoprotein, as well as the whole fish water content were significantly reduced, while the liver total antioxidant capacity, whole fish protein content and muscle shear force values were significantly increased in the SOp, BOl, BOp groups. In addition, the serum catalase activity and muscle hardness of BOp group were significantly higher than those of SOl, BOl and SOp groups. The fatty acid composition of liver and muscle showed little difference among the groups, reflecting the fatty acid profile of feed. The results indicated that compared with liquid oil, fat powder had no adverse effect on the growth of tilapia and could improve the health and muscle quality of fish. The effect of blend oil is better than that of soybean oil. Combined with the advantages of packaging, transportation, storage and usage, fat powder is worth promoting and applying in aquaculture production.