A commercial seaweed extract increases growth performance, immune responses, and related gene expressions in whiteleg shrimp (Litopenaeus vannamei)

Abstract

Seaweed liquid extracts are an attractive source of phytochemicals with high potential applicability in the aquafeed-additive industry. A commercial seaweed liquid extract (True Algae Max, TAM®), which has a marine seaweed odor, also dislplays significant levels of polysaccharides, phytochemicals, phenolic, and flavonoid compounds showing antioxidant activities and DPPH inhibition. This study investigates the impact of diets supplemented with TAM® as a functional additive on the growth, nutrient utilization, immune responses, and immune-related gene expressions of whiteleg shrimp (Litopenaeus vannamei). A total of 750 postlarvae (PL, with an average initial weight of 0.053±0.001 g) were divided into five experimental groups, comprising three replicates per dietary treatment. For an eight-week experimental period, all groups were fed identical diets except for the variation in TAM® inclusion levels. The basal diet (control diet) had no inclusion level of TAM® (TAM0_%). Groups 2–5 each contain TAM® inclusion at levels of 1% (10 mL gk^{− 1} diet TAM_1%), 2% (20 mL gk^{− 1} diet TAM_2%), 3% (30 mL gk^{− 1} diet TAM_3%), and 4% (40 mL gk^{− 1} diet TAM_4%), respectively. The results concluded that TAM® has great potential as a feed additive for whiteleg shrimp, compared to the control group. The group TAM_2% significantly achieved final weight (4.337 g), weight gain (4.287 g) specific growth rate (3.423% / day), feed conversion ratio (1.970), feed efficiency ratio (0.507), and protein efficiency ratio (1.407), compared to the control group (3.900 g, 3.850 g, 3.347%/day, 2.183, 0.458, and 1.270, respectively). Whole-body composition of protein and lipid contents were significantly improved by all TAM group including TAM_2% (51.18% and 4.49%, respectively), compared to the control group (49.38% and 4.15%, respectively). As well as, shrimp in group TAM_2% achieved the highest values of lysozyme (3.92 µg mL^{− 1} ), superoxide dismutase (SOD, 11.92 IU mL^{− 1} ), catalase (CAT, 13.04 IU g^{− 1} ), lipase (31.24 IU L^{− 1} ), and amylase (31.24 IU L^{− 1} ), compared to the control group (3.19 µg mL^{− 1} , 8.80 IU mL^{− 1} , 10.84 IU g^{− 1} , 17.35 IU L^{− 1} , 21.65 IU L^{− 1} , respectively). For gene expressions experiment, four immune-related were performed in this study; Peroxiredoxin (Prx), Prophenoloxidase (PPO1), P53-like protein isoform delta (p53), and Hemocyanin subunit L5 (L5H). The results showed that shrimp in group TAM_2% achieved the highest significant P53 gene transcription compared to the control group or the other TAM groups. Compared to other groups, the TAM_1% group considerably increased PPO1 gene transcription, while TAM_3% displayed the greatest Prx gene transcription. On the other hand, compared to control group, all TAM groups significantly improved L5H gene transcription. In conclusion, the current study revealed that TAM® diet supplementation (20 mL of TAM® per kg diet) represents a promising, eco-friendly, and sustainable feed additive in the shrimp aquadiet industry.