Hemato - Immunological and biochemical parameters, skin antibacterial activity, and survival in rainbow trout (Oncorhynchus mykiss) following the diet supplemented with Mentha piperita against Yersinia ruckeri.

This study was aimed to assess the potential effects of Mentha piperita on the hemato - immunological and biochemical parameters, skin antibacterial activity and protection against Yersinia ruckeri infection in rainbow trout Oncorhynchus mykiss. Fish were divided into 4 groups before being fed diets supplemented with 0, 1, 2 and 3% of Mentha piperita (MP) plant extract for 8 weeks. Dose-dependent increases immune (both in skin mucus and blood serum) and hematological parameters (number of red and white cells, hematocrit and hemoglobin contents), as well as in respiratory burst activity, total protein, albumin, and neutrophil levels in fish fed supplemented diets compared to the control fish. Furthermore, dietary MP plant extract supplements have no significant effect on blood biochemical parameters and enzymatic activities of liver determined in serum of rainbow trout. After 8 weeks the cessation of feeding with MP plant extract, survival rates of 54.4%, 63.6% and 75.2% were recorded in groups which received 1, 2 and 3% of MP plant extract of feed, respectively, compared to 34.6% survivals in the control. This study underlying several positive effects of dietary administration of MP plant extract to farmed fish.

Dietary peppermint (Mentha piperita) extracts promote growth performance and increase the main humoral immune parameters (both at mucosal and systemic level) of Caspian brown trout (Salmo trutta caspius Kessler, 1877).

The effects of dietary administration of peppermint (Mentha piperita L.) on Caspian brown trout fish (Salmo trutta caspius) were studied. Fish were divided into 4 groups before being fed diets supplemented with 0% (control), 1%, 2% and 3% of peppermint extracts for 8 weeks. Dose-dependent increases in growth, immune (both in skin mucus and blood serum) and hematological parameters (number of white cells, hematocrit and hemoglobin content), as well as in amylase activity and in the number of lactic acid bacteria on intestine were recorded in fish fed supplemented diets compared to control fish. However, the dietary peppermint supplements have different effects on the number of blood leucocytes depending on the leukocyte cell type. While no significant differences were observed in the number of blood monocytes and eosinophils, the number of lymphocytes was decreased, respectively, on fish fed peppermint enriched diets, respect to the values found in control fish. Furthermore, dietary peppermint supplements have no significant effect on blood biochemical parameters, enzymatic activities of liver determined in serum and total viable aerobic bacterial count on intestine of Caspian brown trout. Present results support that dietary administration of peppermint promotes growth performance and increases the main humoral immune parameters (both at mucosal and systemic level) and the number of the endogenous lactic acid bacteria of Caspian brown trout. This study underlying several positive effects of dietary administration of peppermint to farmed fish.

Effects of dietary peppermint (Mentha piperita) on growth performance, chemical body composition and hematological and immune parameters of fry Caspian white fish (Rutilus frisii kutum).

Peppermint (Mentha piperita L.) is a very popular herb. While numerous effects have been described in mammals, its effects on fish have received so far limited attention. The effects of dietary administration of peppermint on fry Caspian white fish (Rutilus frisii kutum) were studied. Fish were divided into 4 groups before being fed diets supplemented with 0% (control), 1%, 2% and 3% of peppermint extracts for 8 weeks. Dose-dependent increases of growth parameters (WG and SGR), mucus skin (protein concentration, alkaline phosphatase and antimicrobial activity) and seric (lysozyme and IgM) and blood leucocyte respiratory burst activities and different hematological parameters (number of red and white cells, seric hemoglobin and hematocrit content) were recorded in fry fish fed supplemented diets. However, the dietary peppermint supplements have different effects on the number of blood leucocytes depending on the leucocyte cell type. While no significant differences were observed in the number of blood monocytes and eosinophils, the number of neutrophils and lymphocytes was increased and decreased, respectively, on fish fed peppermint enriched diets, respect to the values found in control fish. Present results corroborate that dietary administration of peppermint promotes growth performance and increases the main hematological and immune humoral (both mucosal and systemic) parameters of fry Caspian white fish. This study may provide new applications of peppermint and, at the same time, promote rational development and utilization of peppermint resources.

A histological and ultrastructural study of the skin of rainbow trout (Oncorhynchus mykiss) alevins exposed to different levels of ultraviolet B radiation.

The current study was conducted to evaluate the effects of UV-B radiation on survival rate and histopathological changes in the skin structure and ultrastructure in rainbow trout (Oncorhynchus mykiss) alevins. In laboratory dark conditions, newly hatched rainbow trout alevins were exposed to two different doses of UV-B radiation (high dose: HD: 94.83 µW cm(-2)) and (low dose: LD: 68.75 µW cm(-2)) for 9 days (time of exposure: 15 min per day), whereas specimens kept in darkness served as a control group. At the end of the experiment, alevins exposed to HD-UVB had the lowest survival rate (43.9 ± 0.9%), whereas fish exposed to LD-UVB showed intermediate values (73.6 ± 0.4%) with regard to the control group (91.2 ± 0.2%). Light microscopic and scanning electron microscopic studies revealed necrosis, sunburned cells, epidermis lifting of the epidermis, reduced number of mucous cells, degeneration of mucous cells and destruction of pavement cell microridges in both UV-B exposed groups. Hemorrhage and inflation in the meningeal layer of the brain were also observed in 17% and 42% of fish exposed to LD- and HD-UVB, respectively.