Effects of medicinal plants Origanum vulgare L. and Aloe vera on immune system of rainbow trout (Oncorhynchus mykiss)
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Ghorban Sasani, Hassan
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AbstractIn recent years, according to increase in consumption of fish in the world, however, due to the lack of control of many common diseases with disease-causing pathogens, the total world production of fish is threated in aquaculture industry. Rainbow trout (Oncorhynchus mykiss) is one of the most preferred species in aquaculture of Iran. Development of an economical artificial to accelerate the growth and to maintain the health status of this fish is of major importance for sustainable rainbow trout culture. Fish diseases are a serious threat to economic viability of any aquaculture practice. Currently, the commercial aquaculture industry prefers to reduce the costs of production. Because the cost of antibiotics used for prevention and treatment of diseases, and excessive use of growth hormones for improving growth performance is very high. However, the development of antibiotic resistant bacterial strains, accumulation of residue in cultured fish and environmental problems associated with the use of chemicals have led to investigate on suitable methods of disease management. Therefore, a new approach to immunotherapy is actively used to prevent or treat fish diseases, increased disease resistance, feed efficiency and growth performance of fish in a sustainable aquaculture industry. In this regard, extensive research has been carried out to test the new compounds led to the development of the aquaculture industry. It has been proved that use of medicinal herbs in fish diet enhance the immune system against infections with various bacteria, especially, Aeromonas hydrophila in different species of fish, which is of the major bacterial pathogens, leading to heavy mortality rate and decrease the productivity efficiency, causing high economic loss of the fish farmers. The aim of this study was to evaluate the effects of aqueous-alcoholic extracts of two medicinal herbs, Origanum Vulgare L. and Aloe vera on the immune system of rainbow trout (Oncorhynchus mykiss). Aqueousalcoholic was prepared by percolation method and concentrated. After, they were dried by dry evapory. The study was conducted in two stages. First, 1200 of rainbow trout (Oncorynchus mykiss) fry with an average initial weight of 13 ±0.05 g, and the second, 2400 of fry rainbow trout with an average initial weight of 2±0.13 g. At each stage, the fish in 4 groups: 1) placebo-treated group (negative control), 2) treatment with Origanum vulgare extract, 3) treatment with Aloe vera extract and 4) treatment with levamisole (positive control). Each group was consisted of three replicates. Fish were distributed in 12 circular concrete tanks with volume 1000 liters of water and flow 2.5L per second. In the first phase were used of 100 fish 13 grams and the second phase of 200 fish 2 grams. During the experiments, a number of physico-chemical factors, including water temperature, dissolved oxygen and pH were measured. In this study, Origanum vulgare, Aloe vera extracts and placebo (70 % lactose, 10 % starch and 20 % talc) were used at a rate of 1% and levamisole at a rate of 0.1% of weight feed at a rate 2% of body weight. At each stage of the experiments, each group of fish were fed once a day and in the first feeding for 10 weeks. Other promises were fed with regular food (no additives). During the experiments, the fish were weighed weekly throughout the biometry and measured every 2 weeks. To measure the weight, total biomass of fish from each replicate was divided the number of fish in the same replicate. To measure the length from each replicate 15 fish were randomly netted and anaesthetized with 50 mg/L of tricaine methanesulfonate (MS222, Sigma Chemical Co. St. Louis, MO, USA) and then the mean was calculated. During bleeding, fish were rapidly netted, tranquillized with 50 mg/L of MS222. Fish 13 gram were bled from caudal vein using 1 ml insulin syringe fitted with 24 gauge needle and 2 gram by cutting the caudal. To minimize the stress to fish, 1 ml of blood was drawn and the whole bleeding procedure was completed within 1 min. A total number of 15 blood samples were collected from 15 fish from each group (5 fish from each replicate) at the end of every 2 weeks, 24 h after final feeding period for the analysis of the hematological and serological parameters. The blood pooling of 5 fish from each replicate divided into 2 haves. Half collected in serological tubes containing a pinch of lithium heparin powder, shaken gently and kept at 4ºC to test hematological parameters. Other half collected in tubes without of anticoagulant and allowed to clot at 4ºC for 2hrs to test serological parameters. The clot was the spun down at 2000g for 10 min to separate the serum. The serum collected by micropipette and was stored in sterile Eppendorf tubes at -20ºC until used for assay. Blood samples for measurement of hematological parameters including red blood cell count (RBC) and white blood cell count (WBC), differential cell counts (monocytes, lymphocytes and neutrophiles), and blood indices, mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC), percentage of hemoglobin (Hb) and hematocrit (Hct), and also blood biochemical parameters including serum total protein, albumin, globulin and also immunological parameters such as lysozyme activity, phagocytic activity and respiratory burst activity were done. The results showed that there were not significant differences in hematological parameters between experimental groups with placebo group in identical weeks (p>0.05), but there were significant differences in biochemical parameters and immunological parameters between experimental groups with placebo group in identical weeks (p<0.05). Levels of serum total protein, albumin, and globulin and also lysozyme activity, phagocytic activity and respiratory burst activity were higher in experimental groups than placebo group in identical weeks. Immunology indicators of changes were compared between the two groups of fish 13 g and 2 g at the end of the eighth week after feeding. The results were indicated that the response of the respiratory burst activity; phagocytic activity and serum lysozyme activity were higher in juveniles of 13 gram than juveniles 2 gram. In conclusion, dried Origanum Vulgare and Aloe vera extracts at a rate of 1% of weight feed increased specific and non-specific immune systems in rainbow trout (13 and 2 gram) in identical weeks (2, 4, 6, 8 and 10). Therefore, these extracts can use to enhance immune system in aquaculture industry.
Publisher or UniversityIranian Fisheries Science Research Institute
Series : Nr46462;