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IntroductionThe ornamental clownfish Amphiprion ocellaris (Pomacentridae) (A. ocellaris) is one of the most popular ornamental marine teleost species. They are artificially bred worldwide to satisfy the demand for the ornamental fish as well as to reduce the catching pressure on the natural ornamental fish stock. In Vietnam, this species was successfully bred and grew in captivity, however, growth and survival rates are still low. Researches have revealed that antibiotics may boost growth and improve feed consumption [1]. In contrast, the use of chemicals and antibiotics carries many risks including toxicity, resistance, residues and possible harm to human health [2]. This has paved the way in finding new replacements for antibiotic [3]. Besides vaccine, probiotics and prebiotics, such as mannan oligosaccharides (MOS) have received high attention.Prebiotics are non-digestible, but it benefits the host by increase in growth and metabolism of healthy intestinal bacteria of the host [3]. Previous research showed prebiotics can boost growth of many aquaculture species [4][5][6][7][8][9][10], boost non-specific immune and pathogen resistance [11] and improve intestinal function and health [4,10,12]. MOS is used commonly in fish and crustacean diet.There are many studies on effects of MOS on aquatic species, however, to the authors' knowledge, MOS requirement for optimal growth of clownfish is still poorly understood. Inclusion dosage of the prebiotics plays a vital role because inappropriate dose may adversely affect the animals [4,13]. Therefore, the present study aimed to define the optimal range of MOS inclusion in diets on growth performance and protein content of clownfish, A. ocellaris.
Materials and methods
Experimental fish and culture systems
Results:The result showed that growth rate was enhanced significantly in fish fed 0.10% and 0.15% MOS in diets compared to fish fed other MOS levels or control (P < 0.05). Survival rate significantly increased in fish fed diets with 0.20% and 0.25% MOS, compared to control. Fraction rates of protein growth were significantly higher in fish fed diets with 0.15%, 0.20% and 0.25% MOS supplementation than those fish fed other MOS inclusion levels and the control (P < 0.04). Dietary MOS concentrations and clownfish growth rates were significantly correlated. Optimal MOS concentration was predicted to be 0.185%, 0.173% and 0.171% at Days 14, 42 and 70, respectively.
Conclusions:In conclusion, MOS-supplemented diet benefits for boosting growth, survival and body composition of the clownfish, A. ocellaris.