Influence of Body Size on Blood Hemogram in Rainbow Trout Oncorhynchus Mykiss (Walbaum, 1792)

Aim: The aim of this study was to investigate the influence of body size on hematological parameters in Rainbow trout Oncorhynchus mykiss (Walbaum, 1792). Materials and Methods: For the purpose of the study, fifty Italian trout were divided into two groups: Group S1 (n=25) of weight (300-500 g) and length (25-32 cm); Group S2 (n=25) of weight (510-700 g) and length (33-38 cm). Blood samples were collected from each fish, to record the count of white blood cell (WBC), red blood cell (RBC), determine the hemoglobin concentration (Hb), hematocrit (Hct) value, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) mean corpuscular hemoglobin concentration (MCHC), and thrombocyte count (TC). Results: The collected blood was analyzed using an automatic method to determine the hematological parameters. Statistical analysis (unpaired t-test) showed a significant effect of size (p<0.05) on the RBC count, Hb concentration and Hct value. No statistically significant differences were observed in the WBC count, MCV, MCH concentration, MCHC and TC. Conclusion: The data reported in this study contributed towards the knowledge of hematological evaluation in farmed trout and showed that fish size was an important factor that helped establish the “physiological range” supporting the accurate interpretation of hematological parameters in examining the health status of this species.