Abstract
Sulfate-based alginate polysaccharide (SAP) is a novelty marine prebiotic. To investigate the beneficial effects of SAP in Pacific white shrimp (Litopenaeus vannamei) fed low-fishmeal diets, six diets (whole fishmeal group: FM; fishmeal replacement with cottonseed protein concentrate and SAP supplementary groups: SAP0, SAP1, SAP2, SAP3, and SAP4) were formulated and fed shrimp for 56 days. The results showed that SAP2 and SAP3 groups reached the best weight gain and specific growth rate ( P < 0.05 ). In serum, the activities of lysozyme and acid phosphatase showed the trend of firstly increased and then decreased ( P < 0.05 ). In the gut, the highest activities of trypsin, lipase, and amylase were found in SAP2 and SAP3 groups ( P < 0.05 ); the histological indexes gradually improved with SAP levels increased ( P < 0.05 ); sequencing of microbiota revealed that the composition and structure of microbiota have been improved, especially in the decreasing abundance of Vibrio, Pseudoalteromonas, and Candidatus Bacilloplasma at genus level. Besides, transcriptomics revealed a degree of similarity in differential gene expression patterns in shrimp; the comparison of RNA-Seq and qRT-PCR verified that SAP improved antioxidant and immunity in shrimp. The challenge revealed that SAP strengthened the resistance against Vibrio parahaemolyticus. Totally, the supplementary SAP to low-fishmeal diets improved growth, intestinal health, and disease resistance in shrimp. Based on the polynomial curve analysis of specific growth rate among SAPs groups, the optimum SAP supplementary level was 1.91%.
Highlights
Pacific white shrimp (Litopenaeus vannamei) is a widely distributed omnivorous crustacean
The maximum and minimum of final weight (FW) appeared in the SAP2 group and SAP4 group, respectively (P < 0:05)
The FCR in the SAP4 group was the maximum between groups, while FCR in SAP1, SAP2, and SAP3 groups was significantly lower than that in other groups (P < 0:05)
Summary
Pacific white shrimp (Litopenaeus vannamei) is a widely distributed omnivorous crustacean. The shrimp performs excellent traits, such as strong adaptability, rapid growth rate, and abundant nutritional value [1]. The shrimp obtains high economic value, which is well popular with the consumer [2, 3]. Aquaculture has made great progress, providing high-quality food protein for the public. According to the statistics conducted by FAO (Food and Agriculture Organization) [6], the global demand for fishmeal has increased year by year, yet the fishmeal production cannot meet the aquatic industry development [7]. Plant protein has broad application prospect and promotion value. Utilizing plant protein to replace fishmeal is one of the solutions for sustainable aquaculture [8, 9]
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