Symmetric dimethylarginine concentrations in healthy neonatal foals and mares.
Authors: Bozorgmanesh Rana, Thornton Jessica, Snyder Jackie, Fletcher Caitlin, Mack Rebekah, Coyne Michael, Murphy Rachel, Hegarty Evan, Slovis Nathan
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: SDMA in Neonatal Foals and Periparturient Mares Symmetric dimethylarginine (SDMA) serves as a marker of glomerular filtration rate and renal function in adult horses, but whether standard reference intervals apply to neonates remained unclear. Researchers collected blood samples from 125 healthy Thoroughbred foals and 104 mares at multiple timepoints—foals at <12 hours, 48 hours, 7 days, and 30 days post-partum, with mares sampled during late pregnancy and at corresponding intervals—to establish age-specific SDMA reference ranges for foals during their first month of life. Foal SDMA concentrations declined dramatically from a median of 70 µg/dL at birth to 18 µg/dL by 3–4 weeks, requiring age-specific interpretation: 0–100 µg/dL for birth, 0–85 µg/dL at 1–4 days old, 0–36 µg/dL at 5–10 days old, and 0–24 µg/dL at 20–30 days old, with foal values remaining elevated above the adult reference range for at least the first 20 days of life. Mare SDMA concentrations fell within standard adult reference intervals regardless of pregnancy status, indicating no significant placental transfer or maternal physiological effect. For practitioners interpreting SDMA values in neonatal foals, using adult reference ranges will lead to false concerns about renal compromise; age-matched criteria are essential to distinguish normal physiological patterns from actual renal disease during the critical first month of life.
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Practical Takeaways
- •Do not interpret foal SDMA values using adult reference ranges—use age-specific thresholds to avoid misdiagnosing normal neonatal physiology as renal dysfunction
- •Foal SDMA naturally declines during the first month of life as renal function matures; serial monitoring may be more informative than single measurements in suspected renal disease
- •Mare SDMA concentrations provide no predictive value for foal SDMA or renal status, so they should be interpreted independently
Key Findings
- •Foal SDMA concentrations decline from median 70 µg/dL at birth to 18 µg/dL by 3-4 weeks of life, remaining above adult reference ranges for at least 20 days
- •Age-specific reference ranges established for foals: 0-100 µg/dL at birth, 0-85 µg/dL at 1-4 days, 0-36 µg/dL at 5-10 days, and 0-24 µg/dL at 20-30 days
- •Mare SDMA concentrations did not differ from general adult horse reference intervals and showed no correlation with foal SDMA concentrations (ρ = 0.06, P = 0.58)
- •Upper SDMA limits in foals exceed adult horse reference intervals for the first 20+ days of life, necessitating age-dependent interpretation