Selected hematological, biochemical, and acid-base variables of Paso Fino horses living at different altitudes

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 P_vCO₂ 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 P_vCO₂ were identified in horses living between 1000 and 3000 masl. This study showed that the Htc, Hb, and P_vCO₂ 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.