The worldwide expansion of aquaculture has resulted in a rising demand for fishmeal and fish oil for the manufacture of aquafeeds. However, relying on these resources is ecologically unsustainable. Therefore, the search for alternative sources of protein has intensified. One such alternative is bacterial-based single cell protein (SCP), which is considered sustainable because it can be produced using a variety of low-cost agricultural by-products and wastes, yielding a product that may contain high levels of protein and an attractive profile of essential amino acids. In the present study, the bacterial-based SCP MRD-Pro® was incorporated into diets for Pacific white shrimp (Litopenaeus vannamei) juveniles.
Based upon a control diet formulated with 21.4% fishmeal and containing 35% total crude protein and 6% crude fat, fishmeal was replaced with a single cell protein called MRD-Pro® (Meridian Biotech, LLC, Lexington, Kentucky, USA), produced by utilizing two different proprietary mixtures of organic coproducts and waste stream feedstocks as substrates. Meridian Biotech, LLC has developed a platform of sustainable and transformative technologies that repurpose low value by-products from multiple fermentation industries to produce value added, multifunctional feed ingredients for a variety of major and niche global markets including aquaculture.
For the first product, MRD-Pro® produced in Kentucky, USA (MRD-Pro®-Kentucky), 0%, 25%, 50%, 75%, and 100% of the fishmeal was replaced on a protein basis. For the second product, MRD-Pro® produced in India (MRD-Pro®-India), 0%, 25%, 50%, and 75% of the fishmeal was replaced on a protein basis. All diets were isoproteic and isolipidic.
Groups of twenty-five juvenile L. vannamei with an overall initial mean weight of 1.87 ± 0.02 g were stocked into 250-L circular tanks (71 cm diameter, 0.40 m2 bottom area, filled to 200 L of seawater) in a recirculating aquaculture system (RAS). The RAS was equipped with aeration, sump tanks, biofilters, sand filters, UV light chambers and in-line heaters. Each experimental treatment was randomly assigned to five replicate tanks. Based upon pre-weighed feed rations, shrimp were fed to apparent satiation following visual cues to monitor consumed feed and adjust the ration daily, which was divided into three portions, administered at 08:00, 13:00, and 19:00 h.
The comparative feeding trial has just finished. The shrimp performance is being evaluated in terms of growth, survival, and feed utilization indices. Laboratory determinations, such as the in vivo apparent digestibility coefficients of the diets and the in vitro activity of trypsin and chymotrypsin from the digestive tract of shrimp in response to diet, are presently underway. In addition, the fatty acid composition of shrimp tissues and diets is being determined. Preliminary analysis of shrimp growth indicates that MRD-Pro® has a high nutritional value for L. vannamei.