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.