INSECT (BLACK SOLDIER FLY) LARVAL MEAL AND OIL AS A SOURCE OF FEED INGREDIENT FOR RAINBOW TROUT Oncorhynchus mykiss

Currently, soybean meal is most commonly used feed ingredient in the aquafeed industry. High replacement of fishmeal with soybean meal in trout diets cause negative impacts on performance. Recent findings indicate that insect meal contains bioactive peptides, which might have role in boosting the immune function and reducing intestinal inflammation in fish. Therefore, the aim of this study was to: (i) evaluate the additive effect of insect protein in plant-based diets; (ii) examine the insect oil as a substitute for fish oil and vegetable oil in diets for rainbow trout. Experiment I: Four diets were formulated to contain a fishmeal (FM) based diet (Control), and three plant-based diet (21% soybean meal) with and without insect meal (IM) (0%, 8% and 16% supplementation level). Experiment II: Four FM based diets wherein fish oil (FO) was completely replaced with either vegetable oil (VO) or insect oil (IO); and one additional insect oil-based diet supplemented with bile acid (1.5% Ox-Bile) (IOB). Rainbow trout (525, average weight: 32 g) were stocked at 25 fish per tank (145-L) in triplicate. Each tank was supplied with 8 L min^-1 of constant temperature (15°C), gravity-fed spring water. Fish were hand fed to apparent satiation twice daily for 10 weeks.

The results showed that in experiment I, growth performance and nutrient utilization parameters were not significantly different among the groups. However, numerically higher growth performance was observed for IM (8%) and control (FM) fed groups than other groups. Fatty acids profile of fish fillet was significantly affected by supplementation of IM. The total polyunsaturated fatty acid (PUFA) of the muscle was influenced by the diet with a significantly higher deposition observed in insect protein supplemented groups.

For the oil study (experiment II), the lowest growth performance and highest feed conversion ratio was observed in the bile acid supplemented diet group (IOB) compared to other groups (Fig 2). Fatty acids profiles of the muscle showed that fish fed insect oil-based diet had the highest total saturated FA (SAT) and docosahexaenoic acid (DHA) deposition than other oil sources (Fig 2). Immune function and fatty acids metabolism related genes and oxidative stress enzymes will be presented. In summary, the insect protein might act as an additive for plant-based diet for sustainable carnivore fish production. Furthermore, the insect oil could be used as an alternative source of oil without any negative impact on the fish performance and fillet quality.