Abstract
Blood chemistry normal ranges in rainbow trout Oncorhynchus mykiss were assessed using an automated blood analyser. Non‐haemolysed serum from the caudal vessel of 45 clinically healthy, randomly selected fish (standard length, mean ± s . e . = 25·82 ± 0·68 cm; body mass, mean ± s . e . = 240·10 ± 19·40 g) were analysed for the following blood chemistry variables: glucose, urea, creatinine, total bilirubin, aspartate aminotransferase (EC 2.6.1.1), alanine aminotransferase (EC 2.6.1.2), alkaline phosphatase (EC 3.1.3.1), creatine phosphokinase (EC 2.7.3.2), lactate dehydrogenase (EC 1.1.1.27), gamma‐glutamyl transferase (EC 2.3.2.2), total protein, albumin, triglycerides, cholesterol, Ca, P, Mg, Na, K and Cl. The analytical method performed failed to assess serum gamma‐glutamyl transferase. Descriptive statistics, normality assessment by means of Kolmogorov–Smirnov test, Gaussian range (mean ± 1·96σ), Gaussian range after square root and logarithmic transformation, 2·5th–97·5th percentile range were computed for each variable. With regard to data distribution, 12 variables out of 19 (glucose, total bilirubin, aspartate aminotransferase, total protein, albumin, triglycerides, cholesterol, Ca, P, Mg, Na and K) were normally distributed. Irrespective of distribution type, 2·5th–97·5th percentile range appeared to be a reliable method in normal range evaluation. Estimates obtained were compared with previously reported ranges. General agreement was noted with some exceptions (glucose, alkaline phosphatase, lactate dehydrogenase, creatine phosphokinase, P and K) possibly due to different acclimation (17–22° C) and analytical (37° C) temperature and to methodology (serum v . plasma; caudal vessel withdrawal v . cardiac puncture). The blood automated analyser proved to be a valuable and reliable instrument for the estimation of blood chemistry over normal ranges in rainbow trout, although caution should be taken when comparing estimates obtained using different analytical techniques and acclimation temperatures, using plasma rather than serum or using different withdrawal methods.