Submitted to: International Symposium on Talipia in Aquaculture
Publication Type: Proceedings
Publication Acceptance Date: 7/12/2006
Publication Date: 9/6/2006
Citation: Lim, C.E., Garcia, J.C., Aksoy, M., Klesius, P.H., Shoemaker, C.A., Evans, J.J. 2006. Growth response and resistance to Streptococcus iniae of Nile tilapia Oreochromis niloticus fed diets containing distiller’s dried grains with solubles. 7th Proceedings International Symposium on Tilapia in Aquaculture. September 6-8, 2006 Veracruz, Mexico. on-line http://ag.arizona.edu/azaqua/ista/ISTA7/Papers/DDGS_Lim.doc
Interpretive Summary: Feed is generally the single largest expenditure in aquaculture operations, and protein is the most expensive component in feeds for fish. Soybean meal (SBM), because of its low-cost, consistent quality and availability and high nutritional value, is the most commonly used plant ingredient in aquaculture feeds. Replacement of SBM with less expensive protein sources would be beneficial in reducing feed costs. Distiller’s dried grains with solubles (DDGS), a by-product of the ethanol distillery industry is less expensive than SBM. Approximately 98% of the DDGS in North America is from plants that produced ethanol for fuel, while the remaining 1 to 2% is produced by the alcohol beverage industry. DDGS has a relatively high protein content (~ 30% crude protein) without the presence of antinutritional factors commonly found in most plant protein sources. At present, DDGS is widely used as a protein supplement in terrestrial animal feeds, but its use in fish feed is limited due to its low content of essential amino acids, especially lysine No studies have been conducted on the effect of dietary levels of DDGS on fish immune functions. This study was conducted to evaluate the influence of the dietary levels of DDGS on growth performances, immune responses and resistance of Nile tilapia to Streptococcus iniae challenge. DDGS can be incorporated in tilapia diet at a level of 20% as a substitute for a combination of SBM and corn meal without affecting their growth performance, body composition, hematological parameters, immune response and resistance to S. iniae infection.
Technical Abstract: This study was conducted to evaluate the effect of dietary levels of distiller’s dried grains with solubles (DDGS) on growth performance, body composition, hematology, immune response and resistance of Nile tilapia to Streptococcus iniae challenge. Five isocaloric diets containing DDGS at levels of 0, 10, 20 and 40%, and 40% DDGS + lysine (diet 1 to 5) as partial replacements of a combination of soybean meal (SBM) and corn meal on an equal protein basis were fed to juvenile Nile tilapia (9.41 ± 0.14 g) in four replicate aquaria twice daily to apparent satiation for 10 weeks. Results showed that of fish fed diet 4 had significantly lower (P<0.05) weight gain than those fed diets 1, 2 and 3, but did not differ from fish fed diet 5. Weight gain of fish fed diet 5 was significantly lower than that of fish fed diet 2 but was not different from those fed other diets. No significant differences were found in feed consumption and survival of fish in various treatments. Feed efficiency of diet 4 was significantly lower than that of diet 1 but was not different from those of other diets. Protein efficiency ratio (PER) of diet 4 was significantly lower than those of diets 1, 2 and 3 but did not differ from that of diet 5. PER of diet 5 was significantly lower than that of diet 1 but did not differ for those of other diets. No significant differences were observed among whole body moisture, lipid and ash. Fish fed diet 4 had significantly lower body protein than the group fed diet 1 but did not differ from those fed other diets. Red and white blood cell counts and hematocrit did not differ among treatments. Plasma protein, lysozyme and post-challenge agglutinating antibody titers against S. iniae were not affected by dietary treatments. Likewise, there were no significant differences among the average number of days to first mortality after S. iniae challenge and cumulative mortality 14 days post-challenge among fish in various treatments. DDGS can be incorporated in tilapia diet at a level of 20% as a substitute for a combination of SBM and corn meal without affecting their growth performance, body composition, hematological parameters, immune response and resistance to S. iniae infection.