Hiran Kanghear, Naret Suanyuk, Rewat Khongpradit, Reungchai Tansakul, Sanan Subhadhirasakul and Kitjakarn Supamattaya

pp. 347 - 358

Abstract

The minimal inhibitory concentration of cinnamon bark oil extract against pathogenic Streptococcus
sp. was 250 ppm. An analysis of the extract by gas chromatography and mass spectrophotometer showed
three active substances, cinnamaldehyde (C₉H₈O) at 83.1 %, coumarin (C₉H₆O₂) at 12.6 % and cinnamic acid
(C₉H₈O₂) at 2.2 %.
An effect of cinnamon bark oil extract on growth and resistance to Streptococcus sp. in sex-reversed
red tilapia after feeding the extract-supplemented diets for 8 week was investigated. Four experimental diets
were formulated to contain the extract at 0, 250, 500 and 1,000 ppm. The fish fed diet supplemented with 250 ppm cinnamon bark oil extract showed the best feed conversion ratio (p < 0.05). Although weight gain and specific growth rate were the same as in the control group (p > 0.05), fish fed 250 ppm extract-supplemented diet showed the highest resistance to Streptococcus sp. After
six weeks, the fish fed diet supplemented with cinnamon oil extract at 1,000 ppm showed abnormal hepatic
cells such as atrophy and degeneration and hepatic sinusoids.

Keywords

• Streptococcus sp.
• cinnamon bark oil
• sex-reversed red tilapia