This work evaluated if dietary supplementation of astaxanthin krill oil (QRILL™ AstaOmega Oil, Aker Biomarine Antarctic AS, Norway) with or without soybean oil to a grower shrimp feed enhances the growth performance of L. vannamei farmed under osmotic stress. Shrimp of 1.08 ± 0.11 g body weight (BW) were reared for 74 days under 135 animals/m2 in 50 outdoor tanks of 1 m3. Half of the tanks operated enclosed by a milky-colored sheeting and the remaining fully exposed. Shrimp were fed a 38% crude protein feed top-coated with astaxanthin krill oil (K) and/or soybean oil (S) at 0K-3S, 1K-2S, 2K-1S, and 3K-0S% of the diet, as fed basis, respectively.
In exposed tanks, mean salinity reached 31 ± 6 g/L compared to 36 ± 4 g/L in enclosed tanks. Shrimp survival was similarly high in both rearing systems (90.6 ± 3.8 and 89.2 ± 5.3% in exposed and enclosed tanks, respectively (Table 1) and was unaffected by oil supplementation (P > 0.05). Shrimp raised in the exposed tanks achieved a significantly higher final BW, weekly growth, gained yield, apparent feed intake (AFI) and a lower FCR (feed conversion ratio) compared to animals in the enclosed tanks. As a result of top-coating feed for the exposed tanks with the 1K-2S oil mix, the highest shrimp final BW (14.03 ± 0.52 g) and yield (1,515 ± 40 g/m²) could be achieved when compared to the enclosed rearing system and all the other diets. Under longer exposure periods to hypersalinity in enclosed tanks, a minimum of 2K-1S was required to maximize BW (10.80 ± 0.63g) when compared to the other enclosed diet groups.