Title : Earthworm vermicompost to enhance shrimp white shrimp litopenaeus vannamei growth and inhibite ahpnd disease in a experimental culture
In Mexico the annual shrimp aquaculture rate production is growing, and thus demands more feeding inputs and diseases inhibitors. Among organic fertilizers, Eisenia foetida solid humus is considered as a great promoter for plankton growth, helping to develop these aquatic organisms. In other hand, the excessive use of antibiotics in aquaculture has negatively affected those species who are farmed (Marshall y Levy, 2011), and also has decreased shrimp growth (Bray et al., 2006) because bacteria are more resistant to antibiotics (Karunasagar et al., 1994). That’s why it is important to find environmental alternatives to reduce shrimp diseases. The aim of this study was to evaluate different solid earthworm vermicompost doses as growth promoter and AHPND inhibitor. Five treatments with three replicates each one was seeded with 120 shrimp larvae in 120L tanks with zero water exchange. The tanks were fertilized with initial doses: control, 0.00mg·L-1 solid Vermicompost [VC], 275, 550, 825 and 1100 mg/L-1. The doses were, thereafter, reduced by half at day fifteen. The experiment lasted 45 days. Growth, Food Conversion Ratio and survival were measured. After the growth experiment, mortality accumulation was evaluated for each treatment when shrimp were challenged against Vibrio parahaemolyticus in three liters bowls with three replicates with 10 shrimp of 1.5g each bowl. Water quality parameters were not constant during the experiment and had significant difference (P>0.05) between oxygen and pH treatments. We found that shrimp reared with the organic fertilizer had the best growth (Figure 1), and the lowest food conversion average. On the other hand, we have that treatment over 550mg/l of vermicompost were effective against V. parahaemolyticus. Less than three shrimps died in these treatments in a period of 72h, contrary to treatments less than 550mg/l who had over 50% of the mortality in the first 18h of the challenge. Control had the highest mortality with 80% of the shrimp dead before the 24h trail. Some studies suggest that vermicompost is an important food resource for juvenile shrimp (Chakrabarty, 2008). This organic fertilizer improves water quality and enhanced phytoplankton production (Bwala and Omoregie, 2009; Chakrabarty et al. 2009). We find that vermicompost is a real option to shrimp growth and can lower productions costs. It also can enhance shrimp survival and increase shrimp production when is used in the first stages of shrimp when it is more susceptible to diseases, but further investigation must be done to find what bacterium conglomerate in the vermicompost acts as inhibitor to AHPND.