22 SEPTEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG Study Results of Dietary Krill Meal Inclusion The effect of inclusion of krill meal on penaeid shrimp performance has been investigated (Cordova-Murueta and GarciaCarreno 2002, Nunes et al. 2011, Sá et al. 2013, Smith et al. 2005, Suresh et al. 2011, Williams et al. 2005) and the benefits are summarized in Table 2. Krill meal as a feeding stimulant Among different feeding effectors commercially used in shrimp feeds (betaine, hydrolysates, squid and crustaceans), crustacean and krill meal are the most efficient drivers of feed intake in tiger shrimp (Smith et al. 2005). Moreover, krill meal increases the number of pellets eaten by whiteleg shrimp in a concentration-dependent manner by promoting longer, rather than faster consumption (Derby et al. 2016). Krill meal as a growth accelerator Rapid growth is one of the most desirable culture parameters in shrimp farming. High growth rates can improve production efficiency, survival rates and yield. This can be achieved through a shorter culture period and greater crop turnover. “Unknown growth factors” are thought to exist in some protein meals derived from marine invertebrates, such as squid, polychaetes, shrimp, krill and mollusks (Cruz-Suarez et al. 1987, Guillaume et al. 1989). The growth-enhancing activity is partly explained by the supply of inorganic elements and nutrient balance having positive influence on feed intake. A growth factor is present in the insoluble protein portion in crustacean-derived ingredients (Smith et al. 2005, Williams et al. 2005). Juvenile tiger shrimp grow 20 percent faster on feeds containing crustacean meal or krill meal (Smith et al. 2005), while growth of shrimp increased from 0.58 g/wk with a basal diet to 1.22 g/wk with diets containing krill meal (Williams et al. 2005). Krill meal enhances culture performance of juvenile whiteleg shrimp fed a soy protein concentrate-based diet containing only 5 percent fishmeal (Sá et al. 2013). A combination of whole squid meal and krill meal at dietary levels starting at 0.5 percent (as is basis) enhances shrimp final body weight. A more pronounced effect is found when incorporation of both feed ingredients sums to 2 percent of the diet. Krill meal in plant-based diets While shrimp feed increases production, it is also costly, making up more than 60 percent of the operational costs of shrimp farming. Between 25 and 40 percent of shrimp feed is protein, which has traditionally originated from fishmeal. However, limited supplies and high prices have increased the interest in plant-based protein diets, mainly using soybean meal. These diets often lack palatability and contain anti-nutritional properties that can depreciate shrimp performance. The minimum inclusion level of krill meal in plant-based feeds to enhance growth is low (Sabry-Neto et al. 2016). A dietary inclusion of 1 percent krill meal is sufficient to enhance feed intake, but acceleration of growth, increased yield and a reduction in FCR is only observed at 2 percent inclusion. Krill meal in animal by-product meal diets Rendered animal by-products such as spray-dried blood meal, meat and bone meal, poultry by-product meal and hydrolyzed feather meal are also common sources of protein in shrimp feeds. They can be included in shrimp feeds at dietary levels that range from less than 5 to more than 20 percent. Some proteins of terrestrial origin are poor feeding stimulants for juvenile whiteleg shrimp (Nunes et al. 2006). Behavioral observations carried out in a Y-maze apparatus indicate that bloodmeal and meat and bone meal can promote some level of attractiveness, but act as a repellent at the time of feed intake (Nunes et al. 2006). In diets for blue shrimp Litopenaeus stylirostris designed to contain 20 percent poultry by-product meal, feed attraction was improved by including 3 percent squid meal or krill meal. However, feed palatability and shrimp growth was only enhanced when krill meal was used (Suresh et al. 2011). Therefore, formulators should be aware of the need to supplement feeds based on a high inclusion of animal by-products with krill meal to account for the poor feeding stimulation caused by feeds containing animal by-product meals as a protein source. Krill meal as a cost saver To fully meet shrimp nutrient requirements, feeds must rely on costly ingredients that include fish oil, soybean lecithin and cholesterol, among others. Krill meal at 5 percent can generate a formula cost savings of more than 10 percent without compromising shrimp growth performance (Nunes et al. 2011). This was achieved by eliminating the dependence on soybean lecithin and reducing the use of fishmeal, fish oil and cholesterol. Cholesterol can be completely removed from whiteleg shrimp diets when 3 percent krill meal is used in combination with a minimum of 5 percent fishmeal. This generated a formula cost saving of 6.1 percent, while improving shrimp performance parameters such as body weight, survival, yield, feed intake and FCR. Conclusions Due to its inherent advantages – i.e. as a feeding stimulant, omega-3 fatty acids bound to phospholipids, highly digestible peptides, naturally pure and stable, sustainably sourced – including krill meal in shrimp feed shows promise to improve shrimp culture performance without adding costs. In particular, in diets low in fishmeal, krill meal’s feed attractants increase palatability and improves growth performance of shrimp. Omega-3 phospholipids present in krill meal assure that fats (cholesterol and triglycerides) are efficiently emulsified and digested, stored in the hepatopancreas and mobilized when needed. Full energy reserves in the hepatopancreas and efficient mobilization ensure the best protection against stress situations. Key Points • In shrimp farming, increasing attention is given to Antarctic krill Euphausia superba, a shrimp-like swarming pelagic crustacean living in the Southern Ocean, to improve yield and stress resistance without increasing production costs. • High-protein krill mill is used as a feed additive in diet formulations as an attractant and shrimp growth accelerator. • Krill meal is a sustainable and pure alternative to fishmeal, consisting of around 11 percent omega-3 phospholipids. • Shrimp produce phospholipids inefficiently and depend on dietary addition for building membranes, fat storage/transport and resisting to adverse growing conditions.
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