APPARENT DIGESTIBILITY OF Rhizoclonium riparium FOR THE PACIFIC WHITE SHRIMP, Penaeus vannamei  

Macroalgae and microalgae have emerged as popular alternative ingredients in the modern aquaculture industry and have shown beneficial effects when incorporated into fish diet formulations. The filamentous alga, Rhizoclonium riparium, though considered by some as a nuisance species, shows potential as an alternative ingredient. It was successfully fed together with other algae in a composite algal mix to Oreochromis mossambicus as a supplement. There is, however, limited information on the possible use of Rhizoclonium riparium as a feed ingredient in penaeid diets. The present study aimed to determine the in vivo apparent digestibility coefficients of Rhizoclonium riparium meal (RM) as a feed ingredient in the diet of Pacific white shrimp, Penaeus vannamei.

Pacific white shrimp weighing 11g were randomly stocked in polyethylene tanks and fed a reference diet and a test diet (consisiting of 30% RM) with 1.0% diatomaceous earth (acid insoluble ash, AIA) used as inert marker. Fecal matter was collected in triplicate. Proximate analysis of the RM, feeds, and pooled fecal matter for dry matter, crude protein, crude lipid, and AIA were used to determine the digestibility coefficients of the nutrients. The dry matter, protein, and lipid digestibility coefficients of the test diet were not significantly different from that of the reference diet (Table 1). The information obtained in this study could promote the use of Rhizoclonium riparium meal as a substitute ingredient in low cost diets for Pacific white shrimp.