Location: Aquatic Animal Health Research2011 Annual Report
1a. Objectives (from AD-416)
The overall objective of this project is to define the nutritional value and nutrient bioavailability of various protein and oil sources to improve feed formulations, decrease feed costs for channel catfish and tilapia and increase the use of U.S. agricultural products/byproducts. Efficient feeding practices to improve fish performance and health will be developed for improved formulations. Objective 1: Determine the nutritional value and nutrient bioavailability of various protein sources (especially distillers' dried grains with solubles (DDGS)) and essential fatty acids and their effects on growth, feed palatability, stress, immune response and disease resistance. Objective 3: Develop feeds and feeding strategies to improve nutrient retention, production efficiency, product quality and fish health.
1b. Approach (from AD-416)
The U.S. aquaculture industry faces numerous challenges including high feed and energy costs, low-cost imports and lower fish prices paid to producers. Among these, feed cost represents the largest expenditure in aquaculture operations, and protein is the most expensive component in fish feeds. Lower cost alternative protein sources to replace fish meal and other expensive protein sources must be identified. Soybean meal (SBM), because of its low-cost, availability, consistent quality, and high nutritional value, is the most commonly used plant ingredient in fish feeds, comprising up to 45% grow-out diets. Distillers' dried grains with solubles (DDGS) is readily available and less expensive than SBM and other conventional protein sources on a protein-cost basis, but its use in fish feeds is very limited. Replacement of SBM or more costly ingredients by DDGS would reduce feed costs. This proposed project will investigate the nutritional value and nutrient bioavailability of DDGS derived from various grain sources, and corn DDGS from ethanol plants for channel catfish and tilapia, define the essential fatty acid (EFA) requirement, optimum ratio of n-3 to n-6 and their effect on gene and protein expression, identify biologically active compounds in DDGS which may improve fish growth and health, and develop least-cost feed and feeding strategies to improve nutrient retention, product quality and health. This project should lead to reduced feed costs, increased use of DDGS, and improved feeding practices which will lead to improved growth and survival and product quality, lower producton costs, as well as increased demand of DDGS.
3. Progress Report
A 10-weeks feeding study with sex-reversed male Nile tilapia using nine diets, the control diet without wheat distiller’s dried grains with solubles (WDDGS) (diet 1), diets containing 10, 20, 30 and 40% WDDGS without lysine supplementation (diets 2-5, respectively), and diets containing 10, 20, 30 and 40% WDDGS with lysine supplementation (diets 6-9, respectively) as replacements of soybean meal (SBM) and corn meal (CM) showed that fish fed diet 5 (40% WDDGS) had decreased weight gain (WG), feed efficiency ratio (FER), protein efficiency ratio (PER), and whole body moisture content, but had higher body fat compared with those fed the control diet (diet 1). Addition of lysine to the diet containing 40% WDDGS (diet 9) significantly increased WG, FER, PER and whole body moisture as well as decreased body lipid to a level similar to fish fed diet 1. Hematological and immunological parameters and mortality after challenge and total mortality 3 weeks after challenge with Streptococcus iniae were not affected by dietary treatment. A 12-week study with channel catfish using the same set of nine diets showed that WG, FER, PER, survival, body protein and hematological variables were not affected in fish fed diet with 20% WDDGS (diet 3) without added lysine. With lysine supplementation, WDDGS levels can be increased to 40% (diet 9) with no adverse effect on these parameters. Fish fed diets containing 20% or more WDDGS with or without added lysine had increased specific antibody response against Edwardsiella (E.) ictaluri and resistance to E. ictaluri infection. Studies to evaluate nutrient bioavailability of four distiller’s dried grains with solubles (DDGS) sources and six other commonly use ingredients for catfish and tilapia were also conducted. Fish were acclimated to the basal and test diets seven days prior to fecal collection. Samples of experimental feeds and feces collected have been analyzed for dry matter, crude protein, energy and chromic oxide content. Amino acid analysis is being conducted. Apparent digestibility coefficient of dry matter, protein, energy and amino acid of different test ingredient will be determined after completion of amino acid analysis. The feeding study on essential fatty acid requirements of Nile tilapia is on-going. These studies which aim to improve the growth performance and fish health, determine nutrient bioavailability of feedstuffs and essential fatty acid requirement.
1. Wheat distiller's dried grains with solubles (WDDGS) is an economical feed alternative in aquaculture. Feed cost is the single largest expenditure in intensive aquaculture operations and protein is the most expensive component in fish feeds. For the aquaculture industry to be profitable and sustainable, feed costs must be reduced. Distiller’s dried grains with solubles (DDGS), the main byproduct of ethanol industry, are readily available at a lower-cost than most commonly used protein sources but their use in fish feeds is limited. DDGS from corn have been found as a promising alternative protein source in fish feeds. Wheat DDGS differs markedly in nutrient content from corn DDGS. No information is available on its use in fish diets. ARS scientists in Aquatic Animal Health Research Unit at Auburn, AL, evaluated the influence of dietary levels of WDDGS on growth performance, feed utilization efficiency and resistance of tilapia and catfish to bacterial infection. Results of this research showed that 30% and 20% WDDGS can be used in tilapia and catfish feeds, respectively, as replacement, on an equal protein basis, for a mixture of soybean meal (SBM) and corn meal (CM) without requiring the addition of lysine. With supplementation of lysine, WDDGS level can be increased to 40% for both species. Dietary inclusion levels of WDDGS with or without adding lysine had no effect on the mortality of tilapia infected with Streptococcus iniae. With catfish, however, regardless of lysine supplementation, inclusion of 20% WDDGS or higher improved their resistance against Edwardsiella ictaluri infection. Replacement of a mixture of SBM and CM in catfish feed with 20% WDDGS and in tilapia feed with 30% WDDGS or 40% WDDGS with added lysine (for both species) reduced feed cost by at least $15/ton. Moreover, incorporation of DDGS in fish diets will also lead to increase in demand and expand the market of the United States DDGS.
Welker, T.L., Lim, C.E., Aksoy, M., Klesius, P.H. 2011. Effect of short-term feeding duration of diets containing commercial whole-cell yeast or yeast subcomponents on immune function and disease resistance in channel catfish, Ictalurus punctatus. Journal of Animal Physiology and Animal Nutrition. doi:10.111/j.1439-0396.2011.01127.x.