Comparison of hematologic variables among Warmbloods, Thoroughbreds, and Western stock horse breeds.

Background: Hematology is a diagnostic tool used to evaluate the health status of horses. However, breed differences are often not considered.

Objectives: The objective was to compare complete blood count variables among Warmbloods, Thoroughbreds, and stock horses (SH).

Methods: Ninety-six healthy horses were grouped by breed (Warmbloods, Thoroughbreds, and SH). Samples were collected through venipuncture for complete blood count analysis. One-way ANOVA with Tukey's tests or Kruskal-Wallis with Dunn's post hoc tests were used to compare hematologic variables among groups.

Results: Warmbloods had a significantly lower total white blood cell (WBC) count (6.08 ± 1.11 × 10/L) and lymphocyte count (1.76 ± 0.41 × 10/L) than Thoroughbreds (7.28 ± 1.45; 2.28 ± 5.16 × 10/L, respectively; P < .001) and SH (7.21 ± 1.18 × 10/L, P < .01; 2.10 ± 5.17 × 10/L; P < .05). Warmbloods had a significantly lower red blood cell count (7.7 ± 0.8 × 10/L) and higher mean corpuscular volume (MCV, 49.4 ± 2.2 fL) than Thoroughbreds (8.42 ± 1.2 × 10/L, P < .01; 47.3 ± 3.0 fL). Warmbloods had lower MCVs than SH (49.4 ± 2.2 vs 51.2 ± 2.6 fL). The mean cell hemoglobin concentration (MCHC) was higher in Warmbloods (35.0, 33.8-36.2 g/dL) and Thoroughbreds (34.9, 33.4-35.7 g/dL) than in SH breeds (34.0, 33.4-35.4 g/dL; P < .001, both). Total protein concentrations were significantly lower in Thoroughbreds (67, 59-80 g/L) compared with SH (71, 64-83 g/dL) (P < .05).

Conclusions: Warmbloods had decreased WBC and lymphocyte counts compared with Thoroughbreds and SH, and Thoroughbreds had increased red blood cell counts. Thoroughbreds had lower total protein concentrations than SH. Clinicians should consider breed differences when interpreting hematologic values.