Long-Term Assessment of Baseline Blood Biochemistry Parameters in Rainbow Trout (Oncorhynchus mykiss) Maintained under Controlled Conditions

SIMPLE SUMMARY: Baseline blood biochemistry parameter values, which are well established for humans and other higher vertebrates, are fundamental for diagnosis. In this study, provided for the first time are baseline biochemical values for rainbow trout maintained under controlled conditions (the density, water temperature and photoperiod were kept constant over time). Fish weight was found to influence the parameters analyzed. These findings permit the advancement of knowledge of blood parameters in fish and provide useful measures for assessing health status. ABSTRACT: Twelve biochemical parameters were measured in serum blood samples from rainbow trout (Oncorhynchus mykiss) maintained under controlled conditions. Forty-five samples were taken every 3 months (T1–T4) over the course of one year to define baseline values. The effect of fish total weight (TW) was also evaluated. Principal component analysis showed a clear separation between T4 and T1, and T2 and T3, indicating an increase in certain biochemical parameters with weight. Linear regression analysis showed how TW significantly explained 11–67% of the variability observed for nine parameters out of 12. Pearson’s correlation matrix showed a significant positive correlation (p < 0.05) between TW and albumin, alkaline phosphatase, alanine-aminotransferase, creatinine, gamma-glutamyl transferase, magnesium, phosphorus and total protein. Furthermore, significant correlations (p < 0.05) between the majority of the biochemical parameters were found, indicating that growth can influence several parameters at the same time. The present study provides several useful baseline values for assessing the health of O. mykiss, indicating that fish weight is an important factor for interpreting the blood biochemical profile.