Fish Meal Replacement in Practical Diets for Pacific White Shrimp (Litopenaeus vannamei) Reared in Green Water Systems
Type of DegreeThesis
DepartmentFisheries and Allied Aquacultures
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A series of experimental studies were conducted with Pacific white shrimp, Litopenaeus vannamei, to evaluate the use of plant protein sources as replacement ingredients for fish meal in commercially manufactured diets for shrimp reared in green water environments. In the first study, juvenile (mean weight + S.D. 0.031 + 0.0005g) shrimp were stocked in 16 0.1-ha low-water-exchange ponds and reared over an 18-week culture period. Four commercially extruded diets formulated to contain 35% crude protein and 8% lipids were evaluated. These diets included 16% poultry by-product meal and varying levels of fish meal (9, 6, 3, and 0%), which was replaced by a combination of soybean meal and corn gluten meal to replace the protein originating from fish meal. At the conclusion of the culture period, there were no significant differences (P>0.05) on any of the production parameters evaluated among the test diets, whereas feeding costs were significantly (P<0.05) reduced as more plant proteins were included in the diets. Mean gross production, final weight, FCR and survival were evaluated at the end of the 18-week culture period. Final values ranged from 5,363 - 6,548 kg/ha, 18.4 - 20.7 g, 1.12 - 1.38 and 84.0 - 94.0 %, respectively. This study demonstrated that fish meal can be completely substituted by alternative vegetable protein sources in commercially manufactured shrimp feeds, without negatively compromising the productive and economic performance of L. vannamei reared in ponds. In the second study, juvenile (mean weight + S.D. 0.74 g ± 0.03, n=30) shrimp were stocked in an outdoor covered recirculating system composed of 24 800-L tanks with 30 shrimp per tank and four replicates per treatment. Experimental treatments included four diets with varying levels of fish meal in the diet (9, 6, 3 and 0%), a plant protein-based diet, and a commercial reference feed. Feeds were commercially extruded and offered as sinking extruded pellets with 35% crude protein and 8% lipids. Production parameters at the end of the study demonstrated no significant differences (P> 0.05) among any of the treatments evaluated. Mean net production, final weight, weight gain (%), FCR and survival were evaluated at the end of an 81-day culture period. Final values for these parameters ranged from 564.4 - 639.0 g/m3, 17.4 - 19.5 g, 2,249 - 2,465 %, 1.07 - 1.20 and 83.3 - 89.2 %, respectively. These results indicate that fish meal can be replaced with solvent extracted soybean meal when diets contain 16% poultry by-product meal. In addition, plant protein sources such as soybean meal, corn gluten meal and corn fermented solubles can be used without affecting shrimp performance in diets with no animal protein sources. Feed costs per unit of production indicate that feed costs can be reduced if fish meal is replaced with alternative protein sources. Findings from these two studies provide evidence that shrimp reared in green water systems can successfully use alternative plant based diets with no fish meal. In addition, it indicates that shrimp have the capacity to effectively use a plant protein based diet without negatively compromising shrimp performance. The use of alternative shrimp diets is therefore recommended as a way to reduce pressure and dependance on fish meal and other animal protein sources, with the subsequent reduction on feed production costs as cheaper, high quality plant ingredients are included. Provided that these reduced feed costs are effectively transferred from the feed companies to the shrimp producers, shrimp producers could gain from better profit margins as cheaper feeds are used. An additional reason for using alternative plant-based diets is that they open an opportunity for new markets that would be willing to pay a higher price, for shrimp fed and produced under more ecologically and sustainable conditions that do not represent a threat to the environment or the human health.