Growth and Immune Response of Pacific White Shrimp Cultured in Low Salinity Water and Fed Diets Containing Different Levels of a Humic Substance

Authors: SIMPSON, KELLY - Auburn University; Garcia, Julio; MARTIN, BRITTANY - Auburn University; DAVIS, D. - Auburn University; BRUCE, TIMOTHY - Auburn University; Beck, Benjamin; KELLY, ANITA - Auburn University; ROY, LUKE - Auburn University

Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2026
Publication Date: 2/3/2026
Citation: Simpson, K., Garcia, J.C., Martin, B., Davis, D.A., Bruce, T.J., Beck, B.H., Kelly, A.M., Roy, L.A. 2026. Growth and Immune Response of Pacific White Shrimp Cultured in Low Salinity Water and Fed Diets Containing Different Levels of a Humic Substance. American Fisheries Society Annual Meeting [ABSTRACT]. Georgia AFS 2026 Annual Meeting, Jekyll Island, GA. February 3-5, 2026

Interpretive Summary: Vibrio parahaemolyticus is a gram-negative bacterium commonly found in estuarine, marine, and coastal environments and is known to induce disease throughout the global shrimp aquaculture industry, including on commercial farms in the Southeastern U.S. states that culture shrimp. Hence, shrimp farmers are interested in strategies that would help them improve survival when this pathogen is identified on their farms. A trial was designed to investigate the possibility of immunostimulant properties and growth of Menefeed 150© humic reed-sedge peat substance offered to Pacific white shrimp (Litopenaeus vannamei) at different dietary levels for 6 weeks, followed by a bacterial challenge against Vibrio parahaemolyticus. Juvenile L. vannamei were stocked at 15 shrimp per tank and fed four different treatment diets four times daily for six weeks. Gene expression from intestine and hepatopancreas samples were analyzed to determine if any immune-related genes were affected by dietary treatment. Remaining shrimp were redistributed within their respective treatments in quadruplicate, and stocked at 15 per tank to carry out a bacterial challenge via reverse gavage injection of V. parahaemolyticus at 1.23 x 108 CFU/shrimp. The negative control group was injected with 100 µL of sterile marine broth, and the positive control group was injected with 1.37 × 108 CFU/shrimp. Shrimp fed any level of MFG 150 had significantly higher survival than shrimp fed the basal diet (p = 0.00502, p = 0.00089, and p = 0.000007, respectively). There was significantly higher weight gain for shrimp fed 1 g/kg MFG 150 than those fed 4 g/kg MFG 150 (p = 0.0289). Gene expression analysis revealed a significant difference between treatments in tumor necrosis factor alpha (tnf-a). Shrimp fed 1 g/kg MFG 150 experienced higher weight gain than 4 g/kg MFG 150. All treatments offered MFG 150 experienced significant protection from a known virulent strain of V. parahaemolyticus compared to the control, indicating the possibility of several benefits for L. vannamei cultured in low salinity conditions which could be of value to farmers that struggle with V. parahaemolyticus infections.

Technical Abstract: Vibrio parahaemolyticus is a gram-negative bacterium commonly found in estuarine, marine, and coastal environments and is known to induce disease throughout the global shrimp aquaculture industry, including on commercial farms in the Southeastern U.S. states that culture shrimp. Hence, shrimp farmers are interested in strategies that would help them improve survival when this pathogen is identified on their farms. A trial was designed to investigate the possibility of immunostimulant properties and growth of Menefeed 150© humic reed-sedge peat substance offered to Pacific white shrimp (Litopenaeus vannamei) at different dietary levels for 6 weeks, followed by a bacterial challenge against Vibrio parahaemolyticus. Juvenile L. vannamei were stocked at 15 shrimp per tank and fed four different treatment diets four times daily for six weeks. Gene expression from intestine and hepatopancreas samples were analyzed to determine if any immune-related genes were affected by dietary treatment. Remaining shrimp were redistributed within their respective treatments in quadruplicate, and stocked at 15 per tank to carry out a bacterial challenge via reverse gavage injection of V. parahaemolyticus at 1.23 x 108 CFU/shrimp. The negative control group was injected with 100 µL of sterile marine broth, and the positive control group was injected with 1.37 × 108 CFU/shrimp. Shrimp fed any level of MFG 150 had significantly higher survival than shrimp fed the basal diet (p = 0.00502, p = 0.00089, and p = 0.000007, respectively). There was significantly higher weight gain for shrimp fed 1 g/kg MFG 150 than those fed 4 g/kg MFG 150 (p = 0.0289). Gene expression analysis revealed a significant difference between treatments in tumor necrosis factor alpha (tnf-a). Shrimp fed 1 g/kg MFG 150 experienced higher weight gain than 4 g/kg MFG 150. All treatments offered MFG 150 experienced significant protection from a known virulent strain of V. parahaemolyticus compared to the control, indicating the possibility of several benefits for L. vannamei cultured in low salinity conditions which could be of value to farmers that struggle with V. parahaemolyticus infections.