Preliminary evaluation of the seaweed Gracilaria cervicornis (Rhodophyta) as a partial substitute for the industrial feeds used in shrimp (Litopenaeus vannamei) farming

The aim of this study was to evaluate the use of Gracilaria cervicornis meal as a partial substitute for the industrial feeds used in shrimp (Litopenaeus vannamei) farming. A total of 90 L. vannamei juveniles (0.34 g) were assigned randomly into nine experimental units at a stocking density of 10 shrimp tank⁻¹ and fed a commercial shrimp feed (CSF; 35% crude protein) as a control treatment, a feed made entirely of G. cervicornis (GCM), and a mixture of equal parts of the commercial shrimp feed and the Gracilaria meal (MIX) for 30 days. Over the first 2 weeks of the experiment, the survival was high (100%) in all dietary treatments. However, at the termination of the feeding trial survival decreased to 40% in shrimp fed GCM, significantly lower (P<0.05) than survival of shrimp fed the commercial diet control (CSF) or MIX treatments (100%). The highest growth performance was obtained in the CSF or MIX treatment groups. The absolute growth increase in these groups was significantly higher than for shrimp fed GCM. Similarly, the specific growth rates (SGRs) of shrimp given feeds containing CSF (5.11% day⁻¹) and MIX (4.71% day⁻¹) were significantly greater (P<0.05) than that of shrimp fed GCM pellets (0.44% day⁻¹). The feed efficiency ratios (FERs) were 64 for CSF, 54.3 for MIX and 3.3 for GCM. The results obtained in this study indicated the effectiveness of using G. cervicornis as a partial substitute for shrimp feeds. To our knowledge, this is the first time that the concept that macroalgae can partially substitute for the industrial feeds used in shrimp (L. vannamei) farming has been demonstrated.