Red cell distribution width values and red cell distribution width‐to‐platelet ratio in Thoroughbred foals in the first 24 hours of life

Objectives To report red cell distribution width (RDW) values, to calculate RDW‐to‐platelet ratio (RPR), and to investigate a possible correlation of RDW and RPR index values in neonatal foals classified as healthy or at risk based on clinical information from a population of foals up to 24 hours of life. Design Retrospective study conducted from records and CBCs of foals born between June and November from 2018 to 2020 foaling seasons. Setting Breeding farm. Animals Three hundred and nine neonatal full‐term Thoroughbred foals. Interventions None. Measurements and Main Results Foals were evaluated by a veterinarian within 15 minutes after birth, and a blood sample was collected within 24 hours of life. Based on clinical information, 88 of 309 foals (28.4%) were considered at risk of perinatal disease, and 201 were healthy. Mean gestational age for the foals was 346.3 ± 9.7 days. RDW values did not differ between groups. Gestational length demonstrated to have a negative correlation with RDW (r = –0.156, P = 0.005) and mean corpuscular volume (r = –0.135, P = 0.01), indicating a link of these variables to foal maturity. RPR index was higher for at‐risk (0.073 ± 0.018) than for healthy foals (0.068 ± 0.014, P = 0.01). Conclusion RPR might be a promising early indicator of disease for the field triage of neonatal foals.