The sensitivity, specificity and predictive value of measuring calcium carbonate in mares' prepartum mammary secretions

Abstract

A colorimetric test kit marketed for water quality analysis was used to measure calcium carbonate changes in diluted prefoaling mammary secretions. Daily samples (1 to 3 ml/day) were obtained from 59 Thoroughbred and Warmblood mares starting 14 days prior to foaling to the day of parturition. The sensitivity, specificity, and positive and negative predictive values of the test were calculated on the data collected from 56 mares and 377 prefoaling mammary secretion samples. The results indicate that this test is both sensitive and specific. The predictive value of a positive test (PVPT; positive test defined as the first occurrence that prefoaling mammary secretion calcium carbonate ≥ 200 ppm) indicated that 51.4% of late term pregnant mares would foal within the ensuing 24-hour period, 84.1% within 48 hours and 97.2% within 72 hours. The predictive value of a negative test (PVNT; negative test defined as prefoaling mammary secretion calcium carbonate < 200 ppm) indicated that 99.6% of late term pregnant mares would not be expected to foal within the ensuing 24 hour period, % within 48 hours and 81.8% within 72 hours. This test is helpful as a prognostic tool in indicating the mare's approaching readiness for birth. It is also an accurate prognostic tool to predict that the mare is not likely to foal within 24h when calcium carbonate < 200 ppm in the diluted prefoaling mammary secretion.