Saliva and plasma metabolome analysis during the five days before foaling in the mare.

Overview

• This study investigated changes in saliva and plasma metabolites in mares during the five days before foaling to identify potential non-invasive biomarkers for predicting parturition.
• The researchers compared metabolite profiles in saliva and plasma, aiming to find real-time, welfare-friendly indicators of the onset of foaling.

Background and Purpose

• Saliva is an attractive biofluid for monitoring animal health because it can be collected painlessly, stress-free, and non-invasively.
• Some metabolites in saliva reflect systemic physiological changes, making it useful for real-time monitoring of bodily events.
• The study aimed to analyze the saliva metabolome of mares during the last five days of gestation to identify metabolites that change before parturition.
• They also compared saliva metabolites with those in plasma to understand their relationship and assess the utility of saliva for monitoring.

Methodology

• Twelve pregnant mares were sampled once daily in the morning, beginning at day 322 of gestation through the day of foaling (day 0, D0).
• Samples specifically from the four days before foaling (D-4) to the day of foaling (D0) were analyzed.
• Both saliva and blood plasma were examined using proton Nuclear Magnetic Resonance (^1H NMR) spectroscopy to identify and quantify metabolites.
• Fifty metabolites were identified in saliva and fifty-one in plasma.

Key Metabolite Changes in Saliva

• Three individual metabolites and three metabolite groups showed significant changes over the five-day pre-foaling period.
• Acetic acid: Showed a significant decrease 3 days before foaling and again on the day of foaling.
• Isovaleric acid: Increased significantly from 4 days before foaling to the day of foaling.
• Lactic acid: Decreased significantly between 3 and 2 days before foaling.
• Other metabolite groups also showed statistically significant day-to-day differences, indicating dynamic metabolic shifts.

Key Metabolite Changes in Plasma

• Plasma showed significant changes in glucose and four metabolite groups over the last five days.
• D-Glucose: Levels significantly increased between 3 and 2 days before foaling and increased again on the day of foaling.
• This suggests glucose metabolism is notably modified in the maternal bloodstream approaching parturition.

Conclusions and Implications

• Saliva metabolite profiles display significant but relatively subtle changes in the antepartum period, reflecting some physiological preparation for foaling.
• However, changes in salivary metabolites were not strong enough or consistent enough to establish predictive thresholds for accurately predicting the exact timing of foaling.
• In contrast, plasma glucose levels demonstrated clearer significant changes immediately before foaling, highlighting its potential as a biomarker.
• The study suggests that practical, non-invasive sensors for glucose monitoring in mares’ saliva or other fluids might be developed to enhance foaling prediction.
• This approach could improve animal welfare by enabling stress-free, real-time monitoring of imminent parturition without blood draws or invasive methods.