KRILL MEAL IMPROVES FEED EFFICIENCY IN JUVENILE Litopenaeus vannamei AND REDUCES RELIANCE ON FISHMEAL AND OTHER COSTLY INGREDIENTS
Previous studies have shown that dietary inclusion of krill meal in diets for whiteleg shrimp, L. vannamei, increases the number of pellets eaten and prolong feed intake. The present study evaluated the amount of fishmeal that can be replaced by soybean meal, when low doses of krill meal are added in diets for juvenile whiteleg shrimp, L. vannamei. The control diet was formulated to contain 15.0% fishmeal, 36.4% soybean meal, 3.0% fish oil, 1.0% squid meal, 0.63% L-Lysine, 0.14% DL-Methionine, 0.26% L-Threonine, and 0.01% cholesterol. From this diet, three other diets were formulated by substituting half of fishmeal for soybean meal (SBM) and adding either 1.0, 3.0 or 5.0% krill meal at the cost of squid meal and cholesterol. Shrimp of 1.13 ± 0.19 g (n = 3,210) were stocked at 100 animals/m2 in 30 outdoor tanks of 1.0 m3 (1.02 m2) and raised for 65 days with experimental diets after a 6-day acclimation period. Shrimp were fed using an automatic feeding device which operated daily between 07:30 am and 05:30 pm. To measure feed attractiveness, harvested shrimp were transferred to five indoor tanks of 0.5 m3 and stocked at 88 animals/m2. Animals were fed twice a day for 7 days using four feeding trays per tank. Feed attractiveness was based on apparent feed-intake responses and consisted of offering all diets simultaneously in the same rearing tank. Each diet was placed individually in a feeding tray rested on the tank bottom opposite to each other. In the end of the grow-out period, shrimp survival was 96.2 ± 3.0% and unaffected by dietary treatment. Final shrimp body weight significantly dropped with fishmeal replacement, but stabilized at 5% krill meal compared to the control diet (P > 0.05). Daily weight gain (0.10 ± 0.01 g) and final shrimp yield (650 ± 41 g/m2) were not statistically different. FCR and the amount of feed delivered was significantly reduced when shrimp were fed 3 and 5% krill meal (P < 0.05). Results from the attractability assay indicated that diets containing krill meal showed a significantly higher apparent feed intake than the control diet. This study demonstrated that a 5% dietary inclusion of krill meal is sufficient to reduce the dependence on fishmeal and other costly ingredients, while maintaining shrimp performance through an improved stimulation of feed intake.