Blood Chemistries Of Healthy, Nephrocalcinosis-Affected, And Ozone-Treated Tilapia In Recirculation Systems     Chun-Yao Chen1, Gregory A. Wooster1, Rodman G. Getchell1, Paul R. Bowser1 and Michael B. Timmons2   1Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY; 2Department of Biological and Environmental Engineering, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY     Blood chemistries of Nile tilapia (pure strain Oreochromis niloticus) raised in recirculation systems were studied.  Plasma samples from 120 healthy tilapia, 30 per season, were collected and twenty-nine blood chemistry parameters were measured.  Besides healthy fish, another 30 nephrocalcinosis-affected tilapia, 30 ozone-treated fish and 30 fish with liver pathology were also examined.  Nephrocalcinosis-affected tilapia differed significantly from healthy fish in most electrolyte and metabolite concentrations, and also in ALT, AST and AP activities.  Ozone-treated fish showed significant differences in electrolyte concentrations and ALT, AST, AP activities.  Fish with hepatic lesions differ from healthy controls only in calcium, phosphate, iron concentrations, saturation of iron binding capacity and plasma protein concentration.  Discriminant analysis reveals good separation for each group of fish.  The number of blood chemistry parameters can be reduced from 28 to 12 without losing the ability to separate the groups (both with 91% percent correct prediction).  Most of the incorrect prediction comes from less satisfactory separation of ozone-treated from healthy fish, due to the lack of apparent adverse impact on health after this treatment.