Electrolytes and pH of Mammary Gland Secretions Assessments to Detect Impending Parturition and Associations With Placental and Neonate Features in Donkeys.
Authors: Magalhaes Humberto B, Canuto Lucas E F, Canisso Igor F
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Predicting parturition in donkeys (jennies) remains challenging in clinical practice, prompting researchers to evaluate whether mammary gland secretion analysis—a well-established tool in mares—could reliably forecast impending foaling. Over one breeding season, 37 multiparous jennies were monitored from day 350 of gestation onwards, with daily pH measurements using a hand-held device and serial electrolyte analysis (calcium, magnesium, potassium, and sodium) of mammary secretions collected in the five days preceding birth. Mammary pH demonstrated strong predictive value with 90% sensitivity for foaling within 24 hours, though specificity was modest at 70%, whilst elevated calcium (>10 mmol/L) offered better specificity (85%) and positive predictive value (72%) despite lower sensitivity (71%). A notable species difference emerged: whilst most mares display a rapid pH drop, 65% of jennies exhibited a slow pH decline profile with mean parturition pH of 6.4 ± 0.02, and a smaller subset (32%) showed a faster drop from pH 7.3 to 6.6 over the final 24 hours. These findings suggest that pH monitoring remains a valuable clinical tool for donkey breeding operations, though practitioners should recognise the predominance of slow-drop profiles in jennies and consider combining pH with calcium assessment to maximise predictive accuracy, particularly given the 97% negative predictive value of pH alone—essentially ruling out imminent foaling when values remain elevated.
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Practical Takeaways
- •pH monitoring of mammary secretions is a reliable practical tool for predicting parturition in donkeys within 24 hours, with excellent negative predictive value for ruling out imminent foaling
- •Unlike horses, most donkeys (65%) show a slow rather than fast pH decline, so practitioners should not apply equine pH drop patterns when managing jenny parturition
- •Calcium concentration measurement adds diagnostic value but is less reliable than pH alone; using both together may improve prediction accuracy for imminent foaling
Key Findings
- •Daily pH measurement of mammary gland secretions showed 90% sensitivity for predicting foaling within 24 hours in jennies, with 97% negative predictive value
- •Calcium concentration >10 mmol/L demonstrated 71% sensitivity and 85% specificity for predicting parturition, with 72% and 84% PPV and NPV respectively
- •65% of jennies displayed a slow pH drop profile with mean acidic pH of 6.4±0.02 at foaling, differing from horses where fast pH drop is more common
- •Significant reductions in sodium and increases in calcium, magnesium, and potassium concentrations occurred leading to foaling; foal sex did not affect gestation length or fetal/maternal weight proportions