Shrimp farming can be a highly lucrative business around the world, but has increasingly been characterized by intensification, with greater inputs of feed. Intensification has increased the risk of disease outbreaks and the proportion of operating costs represented by feeds can be as much as 60 percent. Various strategies have been investigated to address these issues, such as using functional feeds designed to improve the productivity and health of shrimp by additions of supplements. Moreover, researchers are continually evaluating appropriate replacements for more-expensive marine ingredients (Gatlin et al. 2007).

One of the potential constraints in shrimp feeds, however, is the requirement for expensive cholesterol and pigments. Additional supplements such as probiotics, prebiotics, extracts and organic acids to create functional feeds further increases feed cost. Consequently, the purchase of commercial aquafeeds may be out of reach for many small-scale farmers around the world.

Alternatively, farmers can make pellets on site with locally available ingredients and/or using trash fish (Gonzalez and Allan 2007). There are several drawbacks to this practice, such as inefficient use of feeds, leading to water quality deterioration, variable ingredient quality and the potential introduction of pathogens (Kim et al. 2007).

In this situation, a potentially better approach might be to combine the “Aquamimicry” concept that relies on the use of fermented rice bran (FRB) to stimulate natural zooplankton (Romano 2017) with the sole provision of fermented soybeans (FSY) as feed for shrimp. This combination that completely replacesthe need to buy or create pellets is referred to as “Aquamimicry fermented soybeans” (AFSY). Despite being contrary to traditional farming practices, AFSY has been successful in the extensive and semi-intensive farming of black tiger shrimp and whiteleg shrimp in some parts of Thailand, Vietnam, Ecuador and India.

This brief article will describe the overall methodology of pellet-free farming by using AFSY as a potential means to improve the cost-effectiveness and sustainability of shrimp aquaculture. Application of AFSY does not require harsh chemicals or antibiotics because diseases are minimized and water quality improved. Efforts are underway to disseminate this knowledge to farmers throughout the world and to share their experiences, opinions and advice with others (Figs. 1 and 2).

Study Methods

This method relies on implementing the Aquamimicry concept within ponds by adding FRB to stimulate the natural production of zooplankton (particularly copepods) prior to stocking shrimp. To create FRB, rice bran is ground to a fine powder, added to water at a 1:1 ratio and then Bacillus probiotics or hydrolytic enzymes are added with aeration. After 24 hours, an initial application of the mixture is made to ponds at 50-100 ppm. Copepods will bloom within two weeks, depending on water source, temperature and previous pond management, but can be as early as two days. Periodic applications of probiotics to pond water and dragging a chain around the pond bottom should also be done. It is not necessary to have a split-pond design as required for Aquamimicry. More details on this protocol can be found at Romano (2017) and at www.bioshrimp.com.

After the copepod bloom, early post-larvae are stocked at 20/m2, a density that is substantially lower than intensive farms. The exact stocking density depends on pond size, growth rates, water quality and market demand. After stocking, FRB is added daily at 1 ppm throughout the culture cycle to serve two important functions. First, this will create some biofloc to help maintain water quality, but at a much lower scale (< 25 mL/L as measured by an Imhoff cone) than an established biofloc-based system. Second, FRB will support pond zooplankton and act to provide supplemental nutrition to the shrimp. In addition to the post-larvae directly feeding on live feeds, it is believed that the larger and more benthic shrimp consume copepod eggs when they sink to the pond bottom. Once shrimp reach 40-50 g (around 180 days of culture), the crop should be partially harvested to ensure that stocking densities do not become excessive.

To create FSY, soybean meal crumble is fermented with additional ingredients in smaller amounts. An example of this formulation is shown in Table 1 and can be done in simple containers (Fig. 3) or in cement mixers. Other farms use variations of this formulation, based on experience and availability of ingredients. For example, fermented soy sauce can substitute for salt and wheat bran can substitute for rice bran. When applying this mixture to ponds, feeding trays should be used to gauge and adjust feeding rates. Table 2 shows a general feeding schedule, but as a rule, underfeeding is preferred to overfeeding to minimize the negative effects of excess FSY decomposing in the pond.

Reasons for Success

Based on reports from farmers applying this management system, shrimp growth reportedly can be up to 0.5 g/d and survival over 80 percent with no serious disease outbreaks. There are several contributors to the success of this protocol, including improvement in water quality, production of live feeds that are consumed by shrimp and the pretreatment of SBM to improve its nutritional value and palatability.

Copepods are a natural food source of shrimp, containing astaxanthin, amino acids and fatty acids, such as omega-3 fatty acids, that are not found in terrestrial plant-based ingredients, such as soybean meal. Therefore, the consumption of live foods by shrimp is essential, inasmuch as soybean meal is nutritionally inferior to fishmeal in the diets of crustaceans (Taher et al. 2017). In addition to deficiencies in certain nutrients, plant proteins often contain high amounts of antinutritional factors, including phytic acid, non-starch polysaccharides, protease inhibitors and tannins that disrupt nutrient utilization and can impart a bitter taste to the shrimp.

Read the rest of this article in the December 2017 issue of World Aquaculture Magazine here