Development and Application of Grain Distillers Dried Yeast for Pacific White Shrimp Litopenaeus vannamei
Type of Degreethesis
Fisheries and Allied Aquacultures
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In recent years there has been an increasing interest in developing low-cost feeds for the Pacific white shrimp, Litopenaeus vannamei. High prices and limited supply are the main factors that have affected primarily feed manufacturing companies. Therefore, animal and plant-based proteins have been evaluated as protein sources in order to reduce commercial shrimp feed costs. Facing this scenario, the idea of replacing fish meal with alternative protein sources, has reduced the dependence on marine ingredients commonly utilized in shrimp formulations. Fish meal has been used in shrimp diets as an excellent protein source due to its high level of nutrients as well as palatability. Nevertheless, the supply of fish meal have become very limited and most importantly, fluctuations in the price has stimulated alternative feed ingredients to be considered. Generally, animal proteins are more expensive than plant ingredients resulting in a considerable interest to evaluate plant by-products as protein sources. Shrimp formulations have included soybean meal, an acceptable protein ingredient with suitable digestibility and steady supply. However, soy products have a lower nutrient content compared to fish meal with regards to protein, essential amino acids, fatty acids, and minerals. Toward this goal, grain distillers dried yeast (GDDY), a co-product obtained from the bioethanol industry, has been evaluated in sunshine bass and rainbow trout with positive results. Therefore, a series of growth trials were conducted to evaluate the substitution of soybean meal with GDDY in clear and green water systems as well as pond conditions for shrimp culture. Results from these studies suggest that formulated diets containing increasing percentages of GDDY (20, and 30% of diet) with or without lysine supplementation can be utilized as a protein source. Positive results were demonstrated using GDDY up to 30% of diet without affecting growth, feed conversion ratio, and survival in clear water tanks. Consequently, GDDY was assessed up to 15% of diet in green water tanks as well as production ponds. Feed response was acceptable for all commercial shrimp feeds and production parameters were at suitable levels. There were no significant differences between any of the GDDY dietary treatments in either ponds or tank growth trials. Overall, results from these studies reveal that GDDY can be utilized as a promising protein source in combination with soybean meal in formulated diets for Pacific white shrimp, as long as dietary nutrients are well-balanced to meet their requirements. In conclusion, diets formulated with GDDY (up to 30% of diet) as the main protein source, did not impair shrimp performance. Furthermore, utilizing GDDY in commercial feeds might reduce feed costs and most importantly, promotes optimum growth.