OBJECTIVES: Effect of long-term oral administration of three different concentrations (0.5, 1.0, and 2.0%) of micronized β-1.3/1.6-D-glucan derived from oyster mushroom (Pleurotus ostreatus, Hiratake) on biometrical, haematological, biochemical, and immunological indices of half-year-old rainbow trout (Oncorhynchus mykiss) was assessed in the study.
DESIGN: Rainbow trout were feed commercial feed pellets containing β-1.3/1.6-D-glucan in the concentrations of 0.5, 1.0, and 2.0% for 85 days. Biometrical indices consisted in total and standard length, body and liver weight, from which derived somatic parameters such as Fulton´s condition factor and hepatosomatic index were calculated. Haematological parameters were evaluated according to unified methods for haematological examination in fish. Plasma biochemical profile was analysed using biochemical analyser Konelab 20i and Easy Lyte Analyzer. A phagocyte cells metabolic activity (induced chemiluminescence of phagocytes) was determined as an immunological parameter by a microplate luminometric method on Immunotech LM-01T.
RESULTS: No clinical signs of behavioral, respiratory, or neurologic distress were observed in rainbow trout. Fish showed normal feeding behavior. As for biometric parameters, no significant changes in total and standard length, body weight, liver weight, as well as in condition factor and hepatosomatic index of experimental and control fish were found. In the course of the study, weight gains in rainbow trout were similar and continuous. Shifts in PCV (p<0.05), haemoglobin (p<0.05), and MCHC (p<0.01) were found within haematological indices. Plasma concentration of glucose, lactate, total protein, cholesterol, calcium, natrium, potassium (all p<0.05), albumins and chlorides (both p<0.01), as well as catalytic activities of ALT and AST (both p<0.05) were changed in the course of the study. A phagocyte cells metabolic activity (luminol-induced chemiluminescence) in rainbow trout was not altered by oyster mushroom β-1.3/1.6-D-glucan administration.
CONCLUSION: After long-term oral administration of three concentrations of micronized β-1.3/1.6-D-glucan derived from oyster mushroom (Pleurotus ostreatus, Hiratake) shifts in haematological and biochemical profiling were found in half-year-old rainbow trout (O. mykiss) in environmental conditions of a commercial rainbow trout fishery. Biometrical indices were not found significantly altered. No specific effect of β-glucan on immune system response of rainbow trout was found in the study. The use of β-glucan in prosperous, clinically healthy aquaculture is still an issue, nevertheless, its use in breedings endangered by stress stimuli, infectious diseases or adverse environmental factors is indisputable.