Effects of supplementing two species of marine algae or their fractions to a formulated diet on growth, survival and composition of shrimp (Litopenaeus vannamei)

Experimental diets were processed by supplementing either whole algae or algae fractions to a formulated control diet to test their effects on growth, survival and composition of juvenile shrimp (Litopenaeus vannamei). Diatom (Thalassiosira weissflogii) and Nannochloropsis cultures were freeze-dried and partially extracted with acetone into a carotenoid fraction and a residue fraction. Seven diets were prepared by individually adding whole diatoms (T. weissflogii), whole Nannochloropsis, a combination of the whole diatoms and Nannochloropsis, their carotenoid fraction, or their residue fraction, to a control diet. After the eight-week feeding trial, shrimp fed diets containing either the whole diatoms, whole Nannochloropsis, a combination of the two, or their residue fractions, achieved higher (P < 0.05) growth (0.57 to 0.64 g week(-1)) and survival rates (93.8 to 100%) than those fed the control diet (0.46 g week(-1); 79.2%). This enhanced growth effect might not be attributable to the macronutrient composition of the microalgae, because their addition reduced the levels of crude protein, crude lipid, and gross energy in the control diet. The growth rate of shrimp fed diets containing the carotenoid fraction of the diatoms and Nannochloropsis (0.54 and 0.47 g week(-1)) was similar (P > 0.05) to that of shrimp fed the control diet. The addition of whole algae also increased the fatty acid and astaxanthin contents of shrimp tail muscles. The improved growth rates indicate the potential advantages of using dried algae as a feed additive, and the benefits of developing phytoplankton in shrimp ponds. (C) 2009 Published by Elsevier B.V.