Effect of proline supplementation on anti-oxidative capacity, immune response and stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei

An 8-week feeding trial was conducted to evaluate the effect of proline on anti-oxidative capacity, immune response and stress tolerance of juvenile Pacific white shrimp , Litopenaeus vannamei . Six practical low fishmeal diets (15% fishmeal) were formulated to contain graded levels (2.02, 2.14, 2.27, 2.38, 2.49, 2.6%) of l -proline. Each diet was randomly assigned to triplicate groups of 30 shrimps (approximately 0.41   g) and the shrimps were fed 4 times a day to apparent satiation. Growth performance was not affected by proline levels (P   >   0.05). But higher levels of proline increased hydroxyproline content in the whole body (P   =   0.004). And survival after 60   h acute NH 3 stress increased with the increasing dietary proline levels (P   =   0.015). High levels of proline also increased the proline oxidase (POX), nitric oxide (NO), total antioxidant capacity (T-AOC) and phenoloxidase (PO) activities in hemolymph or hepatopancreas after the 60   h NH 3 stress compared to basic group which had lowest proline level. Broken-line analysis showed that the optimal dietary proline requirement of L. vannamei was 2.29%, 2.32% and 2.34% based on PO, POX and 60   h survival after NH 3 stress. These results clearly indicated that 2.29–2.34% of proline in the low fish meal diet could improve anti-oxidative capacity, immune response, NH 3 stress tolerance of L. vannamei , and proline may be a conditionally essential AA for L. vannamei . Statement of relevance This study indicates that proline may be a conditional amino acid for white shrimp under the environment stress, especially when fed with low fish meal diet. The results will contribute to the low fish meal diet study of the white shrimp.