Foal Reference Ranges

Age-specific CBC and serum chemistry reference intervals for foals from birth to one year, in conventional US units. Pick an age to read the intervals, or paste analyzer output to have the values checked against them.

Compiled from Koterba, Drummond & Kosch, Equine Clinical Neonatology (tables 24-1 to 24-3 and 27-2 to 27-5); Harvey et al. 1984, Equine vet. J. 16(4), 347–353; and the Rossdales Laboratories neonatal Thoroughbred panel. Nothing on this page is computed or estimated — every interval is transcribed from a published table.

1 · Age of foal

Brackets are the ages the sources actually publish. Pick the closest one; for a foal between two brackets the younger is the more conservative choice.

CBC & haematology

Serum chemistry

2 · Check values

Paste analyzer output — one analyte per line, name then value. Only values outside the interval for the selected age are reported. The lab's own printed ranges are ignored.

Notes and sources

Where each interval comes from

Koterba is primary for every age-series analyte — it is the only source giving a full birth-to-one-year series in conventional units, and it carries age points the others lack (under 1 hour before nursing, 5 days, adult). Harvey et al. 1984 supplies MCH, the one analyte Koterba does not report. The under-36-hour supplement comes from the Rossdales neonatal Thoroughbred panel and covers analytes no age-series source reports at all, IgG among them.

The source for each analyte is shown in the tables above. Adult leukocyte values come from Jain, Schalm's Veterinary Hematology, 4th ed., 1986, by way of Koterba.

How the intervals were constructed, and where the sources disagree

Koterba publishes intervals as mean ± 2 S.D.; Harvey publishes the observed minimum and maximum alongside mean ± SD. Comparing the two across every shared analyte and age, their intervals overlap by only about 84% on average — so a value sitting close to a boundary here may be inside the interval a different text would give. For a borderline value, treat it as borderline rather than as a clean abnormal.

The electrolyte intervals (sodium, potassium, chloride, TCO₂, phosphorus, calcium, magnesium, anion gap) are derived arithmetically from a mean ± 2 S.D. table, so their bounds are statistical rather than observed. On small skewed samples this occasionally produces an implausible bound — magnesium at 3 weeks derives a negative lower limit, and the checker below will not flag a low magnesium at that age.

Known artifacts in the published tables
  • Magnesium at 3 weeks derives a lower bound of −0.7 mg/dL. Low magnesium is not flagged at that bracket.
  • Cholesterol at 9 months is printed as 11–187 mg/dL. The lower bound is out of step with every neighbouring age and is almost certainly a typographical error for 111, so low cholesterol is not flagged at that bracket.
  • Lymphocytes at 1 month in Harvey's table are printed with an upper bound duplicating the neutrophil row; that source is not used for lymphocytes here.
What the checker will not flag

RDW, MPV, nRBC, reticulocytes, osmolality, lactate and ionised calcium have no published foal interval in these sources. Analyzer sample-quality indices (lipemia, hemolysis, icterus index flags) are not the same measurement as the icterus index in the haematology table and are ignored. Differential percentages are only checked for foals under 36 hours, where the Rossdales panel provides them.

These are population reference intervals derived from healthy foals — not decision thresholds, and not a diagnosis. A value inside the interval does not exclude disease, and a value outside it does not establish one. Interpret alongside the foal's clinical picture, hydration status and serial trend. Verify against your own laboratory's methods before acting on any result.