WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2016 21 for membrane function, lipoprotein transport, hormone production and absorption/transport of fatty acids. Cholesterol uptake and distribution in shrimp depends on the availability of phospholipids. Dietary cholesterol levels can be decreased from 0.35 to 0.05 percent when phospholipid levels are simultaneously increased to 5 percent (Gong et al. 2000). Almost no dietary phospholipids are needed when cholesterol levels are high. In short, penaeid shrimp has an inadequate ability to make phospholipids, choline and omega-3 fatty acids. Krill meal delivers protein and feeding stimulants, phospholipids, choline and omega-3 fatty acids in an all-in-one combination in the form of omega-3 lecithins. This blend of factors makes krill meal particularly attractive as a shrimp feed ingredient to improve growth, stress resistance and survival of larvae, post-larvae and juveniles. (CONTINUED ON PAGE 22) TABLE 1. Characteristics of krill meal that have beneficial effects when incorporated into aquaculture feeds. Parameters Explanation Effects of krill meal/astaxanthin krill oil References Cholesterol replacement Cholesterol is expensive and availability inconsistent. Shrimp have limited ability to make cholesterol and show reduced growth, if insufficient cholesterol is present in the diet. ↑ Growth without dietary cholesterol Unpublished results Consumer sensorial preference Optimizing feed ingredients of diets can affect not only the animal’s zootechnical performance, but also the qualitative characteristics of the final product such as color, texture and flavor. ↑ Natural color in end product ↑ Flavor in end product ↑ EPA/DHA content in shrimp tails Castro et al., 2016 Submitted for publication Feeding stimulation Different attractants are used to stimulate shrimp to feed. Krill meal is a chemostimulant that increases the feeding time (not the speed) and thus the amount eaten. ↑ Feed intake ratio ↑ Weekly growth Derby et al., 2016 Smith et al., 2005 Growth accelerator A growth factor was found in the insoluble protein fraction of krill meal. ↑ Weekly growth ↓ Feed conversion ratio Williams et al., 2005 Hypersalinity stress Osmotic stress leads to slower shrimp growth, poor feed conversion ratio and lower survival. ↑ Growth in hypersaline conditions Castro et al., 2016 Submitted for publication Poultry protein diets Poultry by-‐product meal is used as replacement for fish meal in some shrimp feed, but palatability and feed intake are challenges. ↑ Palatability ↑ Attractability ↑ Weekly weight gain Suresh et al., 2011 Plant protein diets Vegetable-‐based diets are used as replacement for fish meal in some shrimp feeds because of increasing fish meal prices and market volatility. ↑ Feed intake ↑ Growth ↑ Yield ↑ Final body weight Sabry-‐Neto et al., 2016 Sustainability Historically, fish meal has been the main source of protein in shrimp feed. With reduced wild catch due to over hunting, a new sustainable attractant for shrimp feed is needed. ↑ Sustainability ↑ Fish in the sea ↓ Need for wild caught fish for fish meal Waite et al., 2014 TABLE 2. A summary of studies indicating the benefits of including krill meal in shrimp diets.
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