Age- and gender-related variations in hematology, clinical biochemistry, and hormones in Spanish fillies and colts

In order to assess which laboratorial parameters need specific age- and/or gender-related reference values, hematological and biochemical profiles (including hormones) were performed in 205 Spanish foals of 5 groups: A (1-2 months; 20 fillies, 10 colts), B (2-3 months; 24 fillies, 18 colts), C (3-6 months; 25 fillies, 16 colts), D (6-9 months; 20 fillies, 23 colts) and E (9-12 months; 25 fillies, 15 colts). Additionally, 120 adult horses were sampled in order to establish baseline data for this breed in our laboratory. Group E had lower red blood cell number and mean cell volume than B, C and D, and neutrophil count was lower in A. Albumin was lower in A than in D, lactate was higher in B, C and D, CK, AST and K were higher in C. In D and E, cortisol was lower and adrenaline was higher. Urea progressively increases, whereas ALP decreases with age. Packed cell volume was higher in fillies of group A, creatinine was higher in colts of group E and fillies of groups B, C, and D had higher aldosterone than colts. In comparison to Spanish adult horses, mean cell volume, albumin, urea, CK, AST, LDH, and ALP requires specific ranges for foals.