This study aimed at describing selected hematological, biochemical, and acid-base variables of adult horses living at sea level and comparing them to those living at 5 different altitudes. One hundred and thirty-eight healthy Paso Fino horses > 2 years old were enrolled. Altitudes included the following: altitude A (0 to 50 m above sea level, masl; n = 23), B (1000 to 1050 masl; n = 25), C (1450 masl; n = 30), D (1950 to 2050 masl; n = 30), and E (2950 to 3100 masl; n = 30). A portable blood gas analyzer was used to determine selected biochemical and acid-base variables. Hematocrit (Htc) was measured by blood centrifugation and total plasma protein as total solids using a refractometer. A one-way ANOVA with Tukey's HSD post hoc test or a Wilcoxon signed-rank test, depending of the normality of the data, was conducted to compare groups. Horses at sea level had lower Htc (25% ± 2) and Hb (8 ± 0.8 mg/dL) concentration than those horses living ≥ 1000 masl (P < 0.05, for all comparisons). No differences in Htc and Hb were identified in horses living between 1000 and 3000 masl (P > 0.05, for all comparisons). The venous PvCO2 was significantly lower in horses living at altitudes ≥ 1000 masl than those living at 0 masl (42 ± 4.8 mmHg) (P = 0.001, for all comparisons). No differences in PvCO2 were identified in horses living between 1000 and 3000 masl. This study showed that the Htc, Hb, and PvCO2 of horses living at sea level were different compared to those in healthy horses living at altitudes ≥ 1000 masl. However, differences in TPP and electrolyte concentrations were not identified.
Keywords: Glucose; Hematocrit; Hemoglobin; Lactate; Metabolic alkalosis; pH.