The benefits of astaxanthin-rich microalgal powder on growth, health, and disease resistance against Fusarium solani in Pacific white shrimp

In shrimp aquaculture, enhancing health and disease resistance is crucial for sustainable production. This study investigates the pioneering effects of astaxanthin-enriched microalgal powder from Haematococcus pluvialis (HP) on Pacific white shrimp (Litopenaeus vannamei), focusing on growth efficiency, body composition, immune and antioxidant responses, intestinal health, histopathology, gene expression, and resistance against Fusarium solani. Shrimp (initial weight 5.27 ± 0.12 g) were separated into four groups and fed diets supplemented with HP at concentrations of 0, 0.5, 1, and 1.5 g/kg feed (control, HP _0.5, HP₁, and HP_1.5), respectively, for 8 weeks. The outcomes revealed marked improvements in growth, feed utilization, and survival rate of the HP-fed groups. The improvement was dose-dependent. The protein and ash content increased and the lipid decreased with HP supplementation. A dose-dependent augmented antioxidant-immune response was obvious in the HP-fed groups. This is proven by the high level of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase, total hemocyte count, respiratory burst, lysozyme (LYZ), phenoloxidase (PO), and phagocytic activity with up-regulation of proPO, LYZ, SOD, and CAT genes. Dietary HP influenced the intestinal bacterial community, where it reduced total aerobic and fecal bacteria and rose total probiotic bacteria and Clostridium counts. Histological investigation showed increased secretory vesicles within B-cells in the hepato-pancreas and larger muscle fibers in the HP-fed groups. Additionally, dietary HP notably lowered mortality rates upon the F. solani challenge, with a reduction from 65.00 % in the control to 45.00 %, 35.00%, and 35.00 % in the HP _0.5, HP₁, and HP_1.5 groups, respectively. Our study recommends adopting dietary HP at the optimal dose of 1.2 g/kg diet relying on the broken line regression model. This study provides valuable insights into the potential of HP as a dietary supplement to improve the health, growth, and disease resistance of L. vannamei, marking a significant advancement in shrimp aquaculture.