Aurantiochytrium limacinum BCC52274 improves growth, hypo-salinity tolerance and swimming strength of Penaeus vannamei post larvae

Long-chain polyunsaturated fatty acids (LC-PUFAs) have been shown to promote growth and health of many larval marine animals. Producing high amounts of LC-PUFAs, thraustochytrids are potential alternatives to fish oil as feed supplement for marine larviculture. Their applications have been assessed in many larval aquatic species but not yet in larval and post-larval (PL) shrimp. Here, growth performance and health of Penaeus vannamei PL were evaluated when fed with a thraustochytrid, Aurantiochytrium limacinum BCC52274 (AL), via enrichment in instar-II Artemia. Instar-II Artemia was enriched with AL for 4 h at the ratio of 400,000 individuals: 600 mg of freeze-dried AL per 1l of 30-ppt water. The feeding experiment consisted of treatment groups fed with varied proportions (from 0 to 100%) of the number of meals offering the non-enriched and enriched instar-II Artemia. Additionally, a reference group was included, in which PL were fed only with instar-I Artemia, the stage commonly used in commercial practice. AL enrichment replenished DHA deficiency in Artemia and increased LC-PUFA content in the fed PL. Increased feeding amounts of the enriched Artemia yielded positive effects on increased biomass gain, longer average length and decreased length variation coefficient of the PL (P < 0.05). The highest growth performance was from the group fed with the highest amount of the enriched Artemia and comparable to that of the instar-I reference group. The supplement resulted in an evident effect on hypo-salinity tolerance of the PL. PL fed with AL were more tolerant to hypo-salinity than those fed with no AL (P < 0.05). From our standardized swimming test, PL fed only with the enriched Artemia also exhibited no negative-rheotaxis swimming, different from the other groups (P < 0.05). AL had no effect on immunology of the PL when evaluated via Vibrio harveyi challenge, phenoloxidase and superoxide dismutase activities (P > 0.05). These findings suggest benefits of AL on growth performance, increasing hypo-salinity tolerance and swimming strength of shrimp PL.