CULTIVATION OF WHITE WORMS Enchytraeus albidus USING LOW- OR NO-COST FEED RESOURCES  

Marine aquaculture relies on live foods for larval rearing of many species. The suitability of an organism for use as a food source depends upon its ease of culture (i.e., cost of cultivation, space requirements, minimal labor, etc.), palatability, and nutritional adequacy. Previous studies suggest that white worms Enchytraeus albidus are a good live food candidate that can be cultured on a variety of low-cost feed inputs, including food processing wastes or expired foods; however, it is not known how these various inputs affect the nutritional value of white worms as live food. Accordingly, we evaluated the proximate and fatty acid composition of white worms fed spent coffee grounds, sugar kelp, mixed expired produce (e.g., various leafy greens), stale bread, or spent brewery grains for 12 weeks. Worm cultures and feed resources were sampled weekly, and results were analyzed using repeated measures ANOVA to determine the significance of feed resource and temporal effects on nutrient composition.

Proximate composition of white worms was significantly affected by feed resource and, to a lesser extent, time. Coffee-fed worms had higher lipid levels (26%) and lower protein (51%) and ash levels (5%) compared to those fed the other feeds, all of which were otherwise compositionally comparable (lipid range=11-15%, protein range=60-68%, ash range = 6-7%). Feed resources also affected worm fatty acid composition, with kelp and produce yielding higher levels of eicosapentaenoic acid (EPA; 16.8 and 14.2 g/100 g fatty acid methyl esters [FAME], respectively) than the other feed resources (2.2-6.2 g/100 g FAME).  A similar trend was observed for arachidonic acid (ARA), which was also higher in worms fed kelp and produce versus the other feed resources (26.3 and 22.6 g vs. 4.5-16.1 g/100 g FAME).  Levels of docosahexaenoic acid (DHA) were very low, regardless of feed resource; however, feeding coffee consistently resulted in more than trace levels (0.4 vs. 0.0-0.1 g/100 g FAME).  

Results indicate white worms can be effectively raised on low- or no-cost feed resources, but that choice of feed resource influences the nutritional value of the resultant worms as live foods.  Feeding coffee yields worms that are higher in fat and contain some DHA, but are lower in protein; whereas, feeding sugar kelp yields worms with higher protein, ARA, and EPA levels, but lower total lipid content. Additional research is warranted to determine the relative plasticity of white worm nutrient profiles and to further develop white worms as an inexpensive, though potentially valuable live food for marine aquaculture.