Growth and fatty acid composition of Pacific oyster (Crassostrea gigas) spat fed a microalga and microcapsules containing varying amounts of eicosapentaenoic and docosahexaenoic acid

Abstract

Pacific oyster (Crassostrea gigas) spat were fed for 28 days on either a 100% ration of the microalga Dunaliella tertiolecta, which lacks fatty acids greater than C18, or an 80% ration of D. tertiolecta and 20% gelatin-acacia microcapsules (GAM). GAM contained corn oil alone or corn oil supplemented with varying amounts of either eicosapentaenoic acid (20:5n-3, EPA), docosahexaenoic acid (22:6n-3, DHA), or combinations of the two. GAM containing either corn oil, corn oil containing up to 0.16% EPA (dry weight of GAM), 0.63% DHA, or 0.32% of an EPA/DHA mixture did not improve shell length, dry weight, or ash-free dry weight (AFDW) of spat compared with spat fed D. tertiolecta alone. However, GAM containing 0.30 and 0.50% EPA resulted in spat with significantly higher AFDW than spat fed either D. tertiolecta alone or D. tertiolecta plus GAM containing corn oil. There was a significant positive correlation between the level of EPA present in GAM and AFDW of spat. The results suggested that spat growth may improve further at levels of dietary EPA higher than those used in this study. The fatty acid profile of spat generally reflected that of the diet after 28 days. However, the increase in dietary levels of both EPA and DHA were not reflected and unfed spat selectively retained EPA and DHA.

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