Hemato-immunological and zootechnical parameters of Nile tilapia fed essential oil of Mentha piperita after challenge with Streptococcus agalactiae

摘要

Essential oils are obtained from vegetal material and present antibacterial activities, antioxidant, antiviral, antifungal properties and may replace the use of chemotherapeutics for treating and prophylaxis in fish farm. The objective of this study was to verify the influence of essential oil of Mentha piperita in the prevention of Streptococcus in Nile tilapia. A total of 300 fish with approximately 5 g were divided into 20 tanks with 15 fish each were fed diet supplemented with essential oil at concentrations of Mentha(0.075%); Mentha(0.125%); Mentha(0.25%) and two controls (commercial feed and feed+ cereal alcohol) in quadruplicate, during 50 days. At the end of the supplementation period, four fish from each experimental unit were collected for hemato-immunological analysis and the rest of the animals were challenged against Streptococcus agalactiae intraperitoneally. During seven days after infection, the fish were monitored every three hours for mortality registration. Zootechnical performance indexes were measured based in the biometries each 15 days along the experimente and did not present significant difference as well as the hematological parameters. Total plasmatic protein was higher in fish fed Mentha(0.125%) than those fed Mentha(0.25%). After the challenge, unlike the animals whose diet did not contain essential oil, the animals that received supplemented ration maintained their alimentary activity. The supplementation with the essential oil increased the resistance of the fish after the challenge with S. agalactiae and survival was significantly higher in fish fed with Mentha(0.25%).