Effect of Oral extract of Mentha longifolia on growth performance and hematological, serum parameter of rainbow trout (Onchorhynchus mykiss) and resistance to bacterial disease

Abstract

In this study, we investigated the effects of oral administration of Mentha longifolia on growth performance, hematological, serum parameters, and resistance to Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). A total of 360 rainbow trout (10.48±0.2 g) were divided into 4 groups and fed with supplemented diets with 0 (control), 0.1, 0.2 and 0.3 % M. longifolia extract in a 4 weeks period. At the end of 4 weeks, 20 fish were selected per treatment and injected intraperitoneally with 0.1 ml (108 cells/ml) of the bacterial suspension. Results showed a significant increase in the final weight, special growth rate, food conversion efficiency, RBC and WBC count, hematocrit (HCT) value, hemoglobin (Hb), total protein (TP) and lysozyme activity in fish fed M. longifolia (especially with 0.2 and 0.3 % concentrations) when compared with control (p<0.05). The lowest mortality was observed in treatment with 0.3 % M. longifolia extract. In conclusion, the oral prescribing of M. longifolia at 0.2 and 0.3 % levels caused improvement in growth performance, some blood and serum parameters, and resistance to Y. ruckeri infection in O. mykiss.

Keywords

• mentha longifolia
• hematological parameter
• growth
• onchorhynchus mykiss