article · Aquaculture International
This study evaluated the effects of dietary astaxanthin on juvenile white-leg shrimp across an eight-week feeding trial, followed by a ten-day bacterial challenge using Vibrio harveyi. Shrimps received feed supplemented with zero, 25, 50, 100, or 200 mg of astaxanthin per kilogram of feed. Shrimp receiving astaxanthin showed significantly higher final weight, weight gain, specific growth rate, and feed intake, with optimum growth observed at 100 to 200 mg per kilogram. Astaxanthin improved gut histology, expanding villi dimensions and absorption area without causing tissue inflammation. In addition, supplemented diets strengthened antioxidant enzyme activities, upregulated relevant antioxidant genes in the hepatopancreas, lowered oxidative stress markers, and elevated several immune parameters including haemocyte count and lysozyme activity. Following exposure to Vibrio harveyi, survival rates increased significantly, reaching 82.7 percent in shrimp fed the highest dosage.
Bacterial infections such as Vibrio harveyi pose major health and productivity challenges in commercial shrimp aquaculture. Demonstrating that a dietary supplement can simultaneously boost growth rates, enhance gut structure, and stimulate natural immune defences gives producers viable dietary strategies to improve shrimp survival and health without relying on conventional antimicrobial treatments.
The findings are directly relevant to aquafeed manufacturers and commercial shrimp farming operations seeking functional feed additives. Dietary astaxanthin at 100 to 200 mg per kilogram of feed showed clear efficacy in promoting growth and resisting bacterial infection. As this was an applied feeding and disease challenge trial in juvenile shrimp, the concept is close to commercial feed formulation and testing in production environments.
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Abstract Astaxanthin (AX) is one of the commonly used feed supplements to enhance the growth performance and provide antioxidant and immune functions of several aquatic animals. In the current study, juveniles of white-leg shrimp ( Litopenaeus vannamei ) with mean initial weight of 0.340 ± 0.041 g were fed with diets supplemented with 0 (control), 25, 50, 100, and 200 mg/kg feed for 8 weeks. At the end of the feeding trial, shrimps were exposed to Vibrio harveyi , and their mortality rates were observed for additional 10 days. The growth indices in the AX-fed groups were significantly ( P < 0.05) higher than what were observed in shrimps in the control group. Dietary AX stimulated the final weight, weight gain, and specific growth rate and optimum growth levels were achieved at 100–200 mg AX/kg feed. Furthermore, the AX-enriched diets significantly enhanced feed intake more than the control diet, and the amount of AX had no effects on feed conversion ratios. In comparison to the control group, the AX-fed animals had significantly ( P < 0.05) higher villi length, villi width, and absorption area and their optimum values were observed at 100–200 mg AX/kg feed treatments. Moreover, the intestinal morphometry especially villi and its crypt, both internal and external tunica muscularis, and submucosal tissues did not show any inflammatory and/or degenerative changes in AX-fed shrimp. Furthermore, the dietary AX at escalating levels linearly and quadratically enhanced ( P < 0.05) the activities of serum superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and increased levels of total antioxidant capacity and reduced glutathione. In addition, malondialdehyde levels decreased significantly in AX-fed animals, and the highest levels were observed in the control group (without AX). The expression levels of cMn-SOD , CAT , and GPx genes were significantly upregulated in the hepatopancreas of L. vannamei fed with AX-enriched diets (especially in the 200-mg/kg feed treatment) as compared with the control diet. The immunity indices of the AX treatments (hematocyte count, total protein, lysozyme, phagocytic activity, and phenoloxidase) of L. vannamei were linearly ( P < 0.05) and quadratically ( P < 0.05) increased. This study revealed the antibacterial activity of AX against V. harveyi abundance. After the bacterial challenge, feeding L. vannamei with dietary AX significantly increased ( P < 0.05) the relative percentage of survival, especially in the treatment of 200-mg/kg diet (82.7%). The findings of the current study demonstrate that dietary AX (100–200 mg/kg feed) was effective in enhancing the growth, antioxidant status, immune response, and increasing the resistance of L. vannamei against V. harveyi infection.
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DOI: 10.1007/s10499-022-00876-w
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