OPPORTUNITIES TO REDUCE FISHMEAL LEVELS IN SHRIMP FEED USING THE RIGHT SOURCE OF SUPPLEMENTAL METHIONINE

Fishmeal (FM) has traditionally been the primary source of protein and amino acids (AA) in commercial shrimp feeds.  However, its limited availability, sustainability concerns, and volatile prices are driving the aquaculture industry towards increased use of alternative vegetable-protein sources. To successfully replace FM, it is required that diets are appropriately balanced for all essential nutrients. In soybean-based shrimp diets, methionine (Met) is typically the first limiting AA and thus supplemental Met sources are routinely used. More recently, a dipeptide of DL-Met (DL-Methionyl-DL-Methionine) or in short 'Met-Met' (AQUAVI^® Met-Met, Evonik Nutrition & Care GmbH, Germany) was specifically developed for shrimps. Previous studies have shown that Met-Met is the most effective source of supplemental Met for shrimps due to its low solubility, leaching and better utilization. Although several studies have been conducted replacing FM levels in shrimp feeds, variable results have been reported. Some of the inconsistent results may be attributed to imbalanced AA profiles and lower efficiency of supplemental Met sources used. Therefore, the objective of this paper is to review the potential of FM reduction in shrimp diets based on 4 recent studies conducted in China, Indonesia, Brazil and Vietnam under different production conditions but with the use of supplemental Met-Met. In all trials, dietary treatments were isonitrogenous and included a "high" FM diet and a "low" FM diet in which the FM level was reduced by 50% of the high FM diet without any supplemental Met but balanced for all other nutrients (Table 1). The low FM diet was then supplemented with increasing levels of Met-Met. Results from all the trials demonstrated that shrimps fed the "low" FM diet without supplemental Met had significantly (P < 0.05) reduced final BW, specific growth rates and increased FCR. However, as the Met deficiency was corrected with the use of supplemental Met-Met, growth performance was restored to the same level achieved by the high FM diets. Overall, these results demonstrate that shrimps do not have a requirement for a specific ingredient such as FM, but rather to specific nutrient levels. In conclusion, FM levels can be successfully reduced in shrimp diets by maintaining an optimal balance of essential AA and meeting the sulfur AA requirements using supplemental Met-Met.