Koh, Chik Boon
(2013)
Effects Of Dietary Organic Acids On Growth Performance Of Red Hybrid Tilapia, Oreochromis Sp., And Inhibition Of Selected Fish Pathogens.
PhD thesis, Universiti Sains Malaysia.
Abstract
Short-chain organic acids have the potential to be viable alternatives to antibiotics by acting as a prophylatic to bacterial disease and enhance fish performance. To test this, three related experiments were set up. The first part of the research was designed to determine the antibacterial effects of various organic acids on Aeromonas hydropilia, in order to develop a tailor-made organic acid blend (OAB). The OAB was then compared with a commercial organic acid product, potassium diformate (KDF) and commonly used antibiotic, oxytetracycline (OTC) on in vitro antibacterial activities to A. hydrophila and Streptococcus agalactiae. All the tested organic acids could completely inhibit A. hydrophila at a concentration of 0.3% or lower. Among the acids, formic acid was the most effective followed by tartaric acid, lactic acid, propionic acid, citric acid and malic acid. The OAB had stronger antimicrobial activity than KDF or OTC when used at 0.2% or higher. It also showed strong bactericidal activity against S. agalactiae. In the second part of the research, two feeding trials were conducted to investigate the practical applications of dietary organic acids in the aquaculture industry. In the second experiment, a 14-week feeding trial was conducted to determine the effects of dietary OAB. The experimental diets were added with 0, 1, 2 or 3 g kg-1 of OAB, or with 2 g kg-1 of KDF and fed to triplicate groups of red hybrid tilapia (Oreochromis sp.). Upon completion, tilapia were challenged by immersion with S. agalactiae. Results showed no significant differences (P>0.05) to growth or nutrient utilization, although a slight improvement was observed for tilapia fed the acidified diets.
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