The relationship between enrichment, fatty acid profiles and bacterial load in cultured rotifers (Brachionus plicatilis L-strain) and Artemia (Artemia salina strain Franciscana)

Rotifers and Artemia are generally used as first foods in marine finfish aquaculture. Because of their poor nutritional value and the incapacity of marine fish to elongate or desaturate 18-carbon of longer polyunsaturated fatty acids (PUFA), it is a common practice to enrich live foods with commercial products. Since live foods represent a significant vector for transmitting bacterial contaminants, this study describes the impact of using different enrichment strategies for rotifers and Artemia on bacterial load, in addition to fatty acid profiles. Rotifers were reared in continuous culture while Artemia were obtained from cysts; both were enriched for 24 h. Total bacterial counts were obtained after a 7-d incubation on marine agar. Docosahexaenoic acid (DHA) levels varied from 9.8 to 34.4% and from 8.3 to 23.2% respectively, for rotifers and Artemia. Eicosapentaenoic acid (EPA) levels ranged from 3.2 to 7.3% for rotifers and from 5.1 to 9.0% for Artemia, while arachidonic acid (ARA) levels varied, respectively, from 0.7 to 2.9 and from 1.4 to 3.7. Total bacterial counts varied from 0.9 × 108 to 56.6 × 108 for rotifers and from 0.2 × 109 to 11.7 × 109 for Artemia. These results demonstrate the importance of the enrichment strategy on the fatty acid composition and the bacterial contamination of live food.