The effects of garlic-supplemented diets on antibacterial activities against Photobacterium damselae subsp. piscicida and Streptococcus iniae and on growth in Cobia, Rachycentron canadum

Abstract

Abstract Photobacteriosis and streptococcosis are the most threatening diseases in cage-cultured cobia, Rachycentron canadum , due to high mortality of 50–80% and annual outbreaks in Taiwan. Garlic, Allium sativum , has long been known to have broad antibacterial properties. This study aimed to examine the in vitro antibacterial activities of garlic and the effects of dietary garlic on disease resistance against Photobacterium damselae subsp. piscicida and Streptococcus iniae and on growth in cobia. The results revealed the marked inhibitory effect of garlic against both P. damselae subsp. piscicida and S. iniae , and feeding garlic diet significantly conferred resistance to challenge with P. damselae subsp. piscicida or/and S. iniae . Cobia fed garlic powder at doses of 0.5 and 1.5 g/kg b.w. for 28 days produced significantly (p P. damselae subsp. piscicida and higher percent weight gain. Cobia fed garlic powder at a dose of 1.2 g/kg b.w. for 21 days and at doses of 0.4 and 1.2 g/kg b.w. for 28 days provided significant (p S. iniae infection. A diet containing garlic powder at a dose of 1.2 g/kg b.w. for 28 days provided significant (p P. damselae subsp. piscicida plus S. iniae combined infection in cobia.