The microbial diseases cause economic losses in aquaculture on global scale and the use of commercial antibiotics for disease treatment produces undesirable side effects. Because many medicinal herbs have evolved potent defense against pathogenic bacteria, there is a growing interest in these herbs as sources for natural antibacterial agents. In this context, green tea (GT), Camellia sinensis L., is considered as a promising source that may be used for improving the growth, survival, and protection of Nile tilapia, Oreochromis niloticus, against Aeromonas hydrophila infection. The present study was undertaken to evaluate the use of GT in practical fish diets and its impact on fish growth and health. GT leaves were ground and added to the ingredients of tested diets to represent 0.0 (control), 0.125, 0.25, 0.50, 1.0, or 2.0 g/kg diet. Fish (1.5–2.0 g) were distributed to various treatments at a rate of 20 fish per 100‐L aquarium and fed one of the experimental diets for 12 wk. After the feeding trial, fish of each treatment were challenged by pathogenic A. hydrophila, and they were kept under observation for 10 d during which abnormal clinical signs and the daily mortality was recorded. The growth‐promoting influences of GT were observed and the optimum growth and feed utilization were obtained at 0.5 g GT/kg diet. The inclusion of GT in fish diet up to 0.5 g/kg diet enhanced the protein contents in fish body, while the lowest lipid contents were obtained at 0.0–0.5 g GT/kg diet. Hematological and biochemical parameters were improved in fish fed 0.25–2.0 g GT/kg diet, while the lowest values were obtained in the control. The survival of fish challenged with A. hydrophila increased with increasing GT level in fish diets. These results indicate that GT supplement is promising immunostimulant, which could improve fish performance, health, and prevent tilapia aermoniosis and the optimum GT level was 0.5 g/kg diet.
A use natural feed additive is becoming useful for fish feeding rather than classic chemical feed additives due to the accumulative effect of the chemical components induced deterrent effects on human health. We study the effects of different levels of dried basil leaves (DBL) on performance, body composition and cost-benefit analysis of hybrid tilapia, Oreochromis niloticus x O. aureus. Four experimental isonitrogenous and isoenergitic diets were formulated to contain 0, 0.5, 1.0 and 2.0% of DBL. Eight glass aquaria (96-L) were used in duplicates to stock ten fish having the same initial weight (13g/fish) in each. Fish were fed 3% of the body weight three times daily, six days a week for 112 days. The dried basil leaves improved digestibility of protein and energy and declined the digestion of lipid and carbohydrates. Incorporation of DBL in test diets improved significantly (P <0.05) growth rate than the control diet especially at 2% DBL which achieved the best inclusion level. Palatability index increased as DBL levels increased and resulted in a reduction in feed waste percent from 33.48% with the control diet to 8.43% with diet contained 2% DBL level. Consequently, low incidence cost and high profit index were significantly (P <0.05) with the diet containing 2% DBL level. There is a positive impact for growth and feed efficiency to use DBL in Tilapia feeds.
Bacterial fish diseases are considered as major constraint in aquaculture production. The use of natural phytochemicals is promising in aquaculture because they are safe for the environment and human health, biocompatible and biodegradable. The present study was carried out to investigate the effect of Ocimum basilicum oil on the non-specific immune response of Nile-tilapia (Oreochromis niloticus) and resistance against Aeromonas hydrophila infection. A hundred and eighty Nile-tilapia (Oreochromis niloticus) (20±2 g/fish) were randomly distributed and divided into four equal groups in well prepared glass aquaria supplied with continuous areation. The 1 st group was assigned as non-treated control group. The 2 nd , 3 rd and 4 th groups were fed on treated ration with basil oil at concentration of 0.25, 0.5 and 1% of basil oil /kg diet for 42 days, respectively. The obtained results showed that the orally administrated basil oil has been shown to enhance the non-specific immune response in the treated fish (hematocrit levels, respiratory burst activity, serum lysozyme and serum bactericidal activity) all over the experiment period in compared with the control group. Also, significant decrease in total bacterial count of fish muscles in compared with control group. Mortality rates post challenge infection, were significantly lesser in treated groups in compared with control group. It was observed that the mortalities among the challenged fish are dose related. These findings are supportive of the potential of basil oil use as ecofriendly alternative measures of disease prevention for sustainable aquaculture. Effect of basil oil (O. basilicum) on nonspecific immune response of Oreochromis niloticus
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