The Effect of Different Storage Temperatures over Time on the pH of Mammary Gland Secretions in Periparturient Mares.
Authors: Canisso Igor F, Amorim Gabrielle B A G, Magalhaes Humberto B
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Mammary Gland Secretion pH in Periparturient Mares Understanding pre-foaling mammary gland secretions (MGS) is clinically important for assessing colostrum quality and foal welfare, yet little was known about how pH fluctuates during the periparturient period or how sample storage affects measurement reliability. Canisso and colleagues monitored 23 multiparous mares from late gestation through the first postpartum week, collecting MGS samples and measuring pH across multiple timepoints whilst also analysing electrolyte concentrations (calcium, magnesium, sodium, potassium) to characterise the physiological transition to lactation. The research revealed that most mares exhibited sodium–potassium inversion and acidic pH at foaling, with postpartum milk pH remaining neutral for approximately four days before becoming slightly alkaline; critically, storage temperature significantly affected pH readings for samples near the neutral point (pH ~7.5 increased to ~8 after storage), whilst samples at more extreme pH values remained relatively stable. These findings have important implications for practitioners collecting pre-foaling samples for quality assessment—storage conditions must be standardised and samples measured promptly, particularly when initial pH readings sit around 7.5, as delayed analysis could misrepresent colostrum quality and influence management decisions regarding foal supplementation or passive transfer of immunity.
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Practical Takeaways
- •If collecting pre-foaling mammary secretions for assessment, be aware that pH varies widely (6.5–8.0) and storage temperature can affect results, particularly for samples near pH 7.5
- •Sodium-potassium inversion in pre-foaling secretions appears normal in most mares and is not a concerning indicator of colostral quality anomalies
- •Foal colostrum assessment timing matters: milk transitions from acidic prepartum to neutral by day 4, so timing of colostral IgG measurement should account for this pH change
Key Findings
- •pH of mammary gland secretions ranges from 6.5 to 8.0 prepartum and becomes neutral (pH 7) through day 4 postpartum, then slightly alkaline thereafter
- •Majority of mares exhibited sodium-potassium inversion and acidic pH at foaling, with elevated calcium, magnesium, and potassium and reduced sodium concentrations
- •Storage temperature affects pH stability (p < 0.05), with samples at ~pH 7.5 showing increase to ~pH 8 post-storage, while other pH ranges showed minimal variation
- •Milk pH remains neutral up to 4 days postpartum with undetermined clinical significance of subsequent alkaline shift