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Abstract

This study evaluated the effects of different processed brown seaweed on the growth, nonspecific immune responses, and resistance to Vibrio alginolyticus of white shrimp (Litopenaeus vannamei). A basal diet was supplemented with 0.25 and 0.5 g kg-1 of a seaweed hot-water extract (HWE), 2.5 g kg-1 of a heat-treated seaweed meal (HSM), and an untreated seaweed meal (USM). A basal diet without seaweed product supplementation served as the control. In total, five experimental diets were each fed to triplicate groups of white shrimp (initial wt: 5.58  0.03 g) in an indoor static rearing system for 16 wks. After the 16-wk feeding trial, the shrimp were challenged with the pathogen V. alginolyticus. Weight gain and feed efficiency were higher (P < 0.05) in shrimp that were fed diets containing 0.25 and 0.5 g kg-1 of the HWE and HSM than in shrimp that were fed other diets. Shrimp that were fed the HSM diet showed higher phenoloxidase activity than did shrimp that were fed the diets with 0.25 g kg-1 of the HWE and USM and the control diet. Superoxide anion production was higher in shrimp that were fed the HSM diet than in shrimp that were fed the control diet. From 96 to 168 h after the V. alginolyticus challenge, the survival of shrimp that were fed the HSM diet was significantly higher than that of the shrimp that were fed other diets. The results indicate that the HSM can enhance the growth, nonspecific immune responses, and resistance to V. alginolyticus of white shrimp.

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