Abstract
A 6-week feeding trial was conducted to evaluate the effects of dietary supplementation of Rhodotorula mucilaginosa JM-01 in different forms (i.e. LC, live cells; FS, fermentation supernatant; CLS, compound of live cells with fermentation supernatant; SKE, sonication-killed cell-free extracts; HK, heat-killed cells; control, basal diet without R. mucilaginosa) on the growth performance, shell pigmentation, immune responses, and disease resistance of the shrimp Penaeus vannamei. The results indicated that the final weight and specific growth rate of shrimp were significantly improved and the feed conversion ratio was significantly reduced in the CLS and HK groups compared to the control. The redness and yellowness of the ventral body color and shell astaxanthin contents in the LC, CLS, SKE, and HK groups were significantly elevated relative to the control, while the lightness was significantly reduced. The challenge test to Vibrio parahaemolyticus demonstrated that the cumulative mortality was significantly lower than the control in all experimental groups. Compared to the control, acid phosphatase, alkaline phosphatase, total superoxide dismutase, lysozyme, total nitric oxide synthase, and catalase activities and total antioxidant capacity and phenoloxidase contents in the serum of shrimp were significantly higher in all experimental groups except the FS group. The relative expression levels of the proPO, SOD, CAT, LZM, Imd, Toll, Relish, TOR, 4E-BP, elF4E1α and elF4E2 genes in the shrimp intestine were significantly enhanced in the LC, CLS, SKE, and HK groups, but only partially induced in the FS group. When the growth performance, body color, astaxanthin contents, and immune responses of shrimp were considered collectively, the compound of live cells with fermentation supernatant exhibited the greatest beneficial effect. However, the postbiotics, i.e. heat-killed cells or sonication-killed cell-free extracts, would be more suited than probiotics in shrimp farming practice, considering the shell-life for storage and the convenience for transportation.
Published Version
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