Dietary Rosmarinic Acid Improved the Growth, Immunity and Antioxidation of Litopenaeus vannamei

This study investigated dietary effects of rosmarinic acid (RA) on the growth and immunity of Litopenaeus vannamei, and performed hepatopancreatic transcriptomic analysis to explore potential underlying molecular associations. RA was added to basal diet at 0 mg/kg (RA0), 50 mg/kg (RA50), 150 mg/kg (RA150), and 450 mg/kg (RA450) to feed L. vannamei (1.80 ± 0.03 g) for 8 weeks. The RA450 group exhibited higher weight gain and a lower feed conversion ratio than the control (p < 0.05). Serum ACP and ACH50 activities in all RA-supplemented groups (RA50, RA150 and RA450), as well as AKP and LZM activities in the RA150 and RA450 groups, were significantly higher than those in the control (p < 0.05). The RA150 and RA450 groups also showed higher T-AOC, R-cell count, lower MDA content in hepatopancreas, and greater intestinal villus width and muscular thickness than the control (p < 0.05), as well as lower mortality in Vibrio parahaemolyticus challenge (p < 0.05). Transcriptomic analysis showed that DEGs in the three RA-supplemented groups were enriched in metabolism pathways such as arachidonic acid, glycosaminoglycan degradation, fatty acid biosynthesis and peroxisome. Among them, growth-related genes (cyp2l, hexb, hacd) and immune/antioxidant genes (ddo, xdh, npc2, galst, gst3) were upregulated by dietary RA. In summary, dietary RA improved the growth, immune and antioxidant functions of L. vannamei and its resistance to V. parahaemolyticus. The improvements were associated with transcriptional changes in lipid-metabolism-related pathways and immune/antioxidant-related genes. These findings provide a theoretical basis for the application of rosmarinic acid as a green additive in the sustainable aquaculture of L. vannamei.