Location: Aquatic Animal Health ResearchTitle: Growth performance and resistance to Streptococcus iniae of juvenile Nile tilapia (Oreochromis niloticus) fed diets supplemented with GroBiotic - A and Brewtech Dried Brewers Yeast) Author
Submitted to: Journal of Applied Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/11/2011
Publication Date: 8/14/2012
Publication URL: http://handle.nal.usda.gov/10113/56495
Citation: Vechklang, K., Lim, C.E., Boonanuntanasarn, S., Welker, T.L., Ponchunchuwong, S., Klesius, P.H., Wanapu, C. 2012. Growth performance and resistance to Streptococcus iniae of juvenile Nile tilapia (Oreochromis niloticus) fed diets supplemented with GroBiotic - A and Brewtech dried brewers yeast. Journal of Applied Aquaculture. 24(3):183-198. Interpretive Summary: Tilapia are increasingly recognized as the species of choice for intensive aquaculture and are likely to become the most important cultured fish in the world. However, one major problem associated with intensive culture is the increased susceptibility of tilapia to Streptococcus iniae infection that caused an estimated annual loss of over $100 million. Commercially, antibiotics have been supplemented in aqua feeds for treatment and prevention of bacterial disease of aquatic animals. The use of antibiotics can lead to the emergence of antibiotic-resistant bacteria, and contamination in food products and the environment. Consequently, a wide variety of immunostimulants such as Brewtech® dried brewers yeast (BY) and GroBiotic®-A (GB) have been added in diets of some fish species to stimulate immune system function, and/or their resistance to infectious diseases. Thus, this study was conducted to evaluate the effects of feeding diets supplemented with BY and GB on growth performance, proximate body composition, immune response and resistance of juvenile Nile tilapia (Oreochromis niloticus) to S. iniae challenge. Result of this study indicated that weight gain, feed intake, survival and whole body proximate composition of Nile tilapia following 12 weeks of feeding were not significantly affected by dietary supplementation of 1 and 2% BY or GB. The significantly lower feed efficiency observed in fish fed the 1% GB diet was probably not related to dietary treatments. Among the serum immunological components evaluated, only serum complement activity was significantly affected by dietary treatments. Total mortality 20 days after challenge with S. iniae was not significantly affected by dietary treatments. However, fish fed diets supplemented with 1% BY and 2% BY or GB had substantially reduced mortality and mortality ended earlier as compared to those of other treatments. Thus, BY and GB may be beneficial in improving the resistance to tilapia to S. iniae infection. However, more study are needed to confirm these findings.
Technical Abstract: This study was conducted to evaluate the effect of dietary levels of Brewtech® dried brewers yeast (BY) and GroBiotic®-A (GB) on growth performance, proximate body composition, immune response and resistance of juvenile Nile tilapia to Streptococcus iniae challenge. A practical basal (control) diet formulated to contain approximately 32% crude and 6% lipid was supplemented with 1 and 2% of BY or GB. Each diet was fed to Nile tilapia in quadruplicate aquaria for 12 weeks. Weight gain, feed intake, survival and whole body proximate composition of fish were not significantly affected by dietary treatments. Serum total protein, total immunoglobulin, lysozyme and agglutinating antibody titer to S. iniae were not significantly different by dietary supplementation of BY or GB. However, serum haemolytic complement activity (SH50) of fish fed 1% BY was significantly higher than those of fish fed the control diet and diets supplemented with 2% BY or GB. Cumulative mortality of fish 20 days post-challenge with S. iniae was unaffected by dietary treatments. However, fish fed diets supplemented with 1% BY and 2% BY or GB had substantially reduced and earlier cessation of mortality.