Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: January 13, 2009
Publication Date: February 15, 2009
Citation: Lim, C.E., Aksoy, M., Klesius, P.H. 2009. Growth Performance and Resistance to Streptococcus iniae of Nile Tilapia, Oreochromis niloticus Fed Various Dietary Levels of Thiamin. In: Aquaculture America 2009, February 15-18,2009, Seattle, Washington. p. 393. Technical Abstract: Thiamin or vitamin B1 functions in all cells as the coenzyme thiamin pyrophosphate that involves in the oxidative decarboxylation of an alpha-keto acids and the transketolase reactions in the pentose phosphate pathway. Thiamin has been demonstrated to be essential in diets of fish, and quantitative requirements have been determined for several fish species including rainbow trout, Pacific salmon, common carp, channel catfish, turbot, yellowtail and tilapia. Results of the few studies with homeotherms on the effect of thiamin on immune function and disease resistance are contradictory. However, to our knowledge, no studies have been conducted on the effect of dietary levels of thiamin on disease resistance in fish. Therefore, this study was conducted to evaluate the effect of dietary levels of thiamine on growth performance, immune response and resistance of Nile tilapia (Oreochromis niloticus) to Streptococcus iniae challenge. An 8-week feeding study was conducted in flow-through 57-L aquaria with juvenile Nile tilapia (3.6 ± 0.2 g) stocked at a rate of 35 fish/aquarium. Casein (vitamin-free)-gelatin based diets supplemented with 0, 2, 4, 8, 16 and 32 mg thiamin/kg were each fed to fish in four replicate aquaria twice daily to apparent satiation. All fish in each aquarium were counted and weighed at 4 week intervals. At the end of 4, 6 and 8 weeks, 2, 2 and 3 fish/aquarium, respectively, were sampled and bled for determination of serum pyruvate and lactate. At the end of week 8, another 3 and 4 fish/aquarium were bled for hematological and serum immunological assays, respectively. Eighteen fish/aquarium (17 only for fish fed the diet without supplemental thiamin) were intraperitoneally injected (IP) challenged with 100 µL of 10,000 CFU/mL of S. iniae and mortality was recorded daily for 14 days. At the end of the challenge period, four surviving fish/aquarium were bled for measurement of serum agglutinating antibody titers against S. iniae. Results showed that Nile tilapia fed the thiamin-unsupplemented diet had significantly (P < 0.05) reduced weight gain, feed intake, feed efficiency and survival relative to fish in other treatments. These parameters did not differ among fish fed diets supplemented with 2 mg thiamin/kg or more. Body protein did not differ among treatments, but lower body lipid and higher moisture and ash were obtained in fish fed the diet without thiamin supplementation. Fish fed this diet also had significantly lower hematocrit than those fed thiamin supplemented diets, but other hematological variables were not influenced by dietary levels of thiamin. Serum pyruvate at weeks 4, 6 and 8 significantly increased in fish fed the thiamin-unsupplemented diet but did not differ for fish fed other diets. Serum lactate, however, was not affected by dietary levels of thiamin. Serum protein, total immunoglobulin, lysozyme and alternative complement activity, and post-challenge antibody titer were not affected by dietary treatments. Cumulative mortality 14 days post-challenge was significantly higher in fish fed the thiamin-unsupplemented diet but did not differ among fish in other treatments.