The aims of this study were to detect physiological changes in blood biochemical parameters throughout gestation, to compare the findings in nonpregnant and pregnant Lipizzaner mares in early-mid and late pregnancy, and to provide reference values for clinical chemistry parameters in this horse breed. A total of 136 venous blood samples were collected from 20 pregnant and 10 nonpregnant (control) asymptomatic Lipizzaner broodmares for biochemical analyses. Twelve parameters (albumin, total

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... in, urea, triglycerides, glucose, creatinine, alkaline phosphatase, aspartate transaminase, glutamate dehydrogenase, gammaglutamyltransferase, creatine kinase and lactate dehydrogenase) were measured. For the statistical analyses, correlation, analysis of variance and Kruskal-Wallis H-test were used to evaluate the possible associations between parameters. Serum triglyceride levels proved to be significantly different in pregnant mares compared to the control group. Total protein and urea levels significantly decreased, while glucose, triglyceride and glutamate dehydrogenase values increased from approx. the fifth month of gestation until parturition. Four biochemical parameters (albumin, aspartate transaminase, total protein and urea) were lower and three other variables (glucose, alkaline phosphatase and creatinine) were significantly higher in late-term pregnant mares than in mares in early or mid-gestation. It is concluded that reference values not only reflect the species, breed and sex but also the reproductive status of animals. The values of haematological and biochemical parameters in the peripheral blood change dynamically in physiological and pathological conditions. To provide the highest standard of care, veterinarians require appropriate reference values corresponding to the species, breed, sex and reproductive status of the patient. Recent studies have evaluated haemostatic and haematological changes oc-*