Location: Aquatic Animal Health Research2013 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-week feeding study was conducted with sexed-reversed male Nile tilapia using nine diets containing 0 (diet 1, control), 10, 20, 30 and 40% sorghum distillers’ dried grains with solubles (SDDGS) without (Diet 2-5), and with (Diet 6-9) lysine supplementation as replacements of a mixture of soybean meal (SBM) and corn meal (CM). Weight gain (WG), feed intake (FI) and feed efficiency ratio (FER) did not differ among all treatments. Hematological and immunological parameters and mortality after challenge and cumulative mortality 3 weeks post challenge with Streptococcus (S.) iniae were not affected by dietary treatments. Another 8-week study evaluated lipid-extracted distillers’ dried grains with solubles (LE-DDGS) at 0, 20, 30, 40 and 50% without added lysine and 40 and 50% LE-DDGS with added lysine as replacements of SBM in hybrid tilapia diets. Survival was not affected by dietary treatments. Weight gain significantly decreased at LE-DDGS inclusion levels of 40 and 50%. Growth improvement was obtained when lysine was added to the 40% LE-DDGS diet but not for the 50% LE-DDGS diet. However, apparent net protein retention (ANPR) and apparent net energy retention (ANER) were similar for all diets containing LE-DDGS but these were significantly lower than those of fish fed the control diet. Two trials (12 and 9 weeks) were conducted to examine the effect of diets containing distillers’ dried grains with solubles (DDGS), distillers’ dried grains (DDG), distillers' soluble concentrate (DSC) and DDG + DSC as replacement of SBM and corn meal combination on growth and resistance to Flavobacterium (F.) columnare in channel catfish (Ictalurus punctatus). Results suggest that inclusion of corn distillers by- products that contain the DSC fraction improved weight gain and feed efficiency ratio of channel catfish, although not significant for each parameter between trials. The improvement is most likely due to the presence of brewer’s yeast and nucleotides in the diets containing the DSC. Improved survival following F. columnare challenge of channel catfish fed corn distillers by-product formulations for 12 weeks was noted in trial 1 as compared to the control diet. In trial 2 (9 weeks), the fish had an underlying chronic bacterial infection that likely influenced our results (i.e., no improvement in survival following challenge). Another 10-week study evaluating the effect of various ratios of linoleic acid (LA) to linolenic acid (LN) for hybrid tilapia juveniles showed that LA to LN ratio had no significant effect on WG, FER, hematological variables, immune response and resistance of tilapia to S. iniae challenges. Either LA or LN at a level of about 1% will meet the essential fatty acid requirement of tilapia. Linoleic acid alone, however, appeared to promote better growth than LN or a combination LA and LN. Diets containing 1.0% LN or higher but with less that 0.5% LA appeared to provide poor growth performance.
Li, E., Lim, C.E., Cai, C., Klesius, P.H. 2012. Enhancement effects of dietary wheat distiller's dried grains with solubles on growth, immunity, and resistance to Edwardsiella ictaluri challenge of channel catfish, Ictalurus punctatus. Journal of the World Aquaculture Society. 43(6):814-827.