Controlled delay of the expulsive phase of foaling affects sympathoadrenal activity and acid base balance of foals in the immediate postnatal phase.

This research investigates the impact of a short delay in foaling on the newborn foal’s stress response and acid-base balance. Findings suggest that while a 5-minute delay in foaling can influence the release of stress hormone and acid-base balance, it does not significantly alter the overall neonatal acclimatization process.

Research Methodology

The study was conducted on two groups of mares ready to give birth. The first group consisted of six mares whose foaling process was deliberately delayed by 5 minutes by moving them into an unfamiliar environment when the allanto-chorion, the fetal membrane, ruptured. The second group was a control group of five mares that were left undisturbed during birth.

Various metrics related to the newborn foals were analyzed, including time taken to first stand and suckle, heart rate, heart rate variability, and salivary cortisol concentration. Blood was also collected immediately after birth and 30 minutes post-birth for hematological analysis and blood gases.

Findings

• There was no significant difference between the two groups in terms of time taken for the foals to first stand and suckle.
• The heart rate of the foals remained constant during birth but increased within 15 minutes after birth.
• Heart rate variability declined during the first hour post-birth for foals in both groups.
• Immediately after birth, the base excess, which is a measure of total base in the body and its impact on the pH level, was lower in foals from the delay group compared to the control group.
• The concentration of epinephrine, a stress-related hormone, was higher in the delay group immediately after birth. In the control group, this hormone increased from the point of birth to 30 minutes after birth.
• Cortisol, another stress hormone, peaked at 1 hour after birth in both groups.
• White blood cell (leukocyte) and polymorphonuclear neutrophils (PMNs) count decreased from birth to 30 minutes after birth.

Conclusion

The conclusion drawn from the research is that a 5-minute delay in foaling does affect the release of the stress hormone, epinephrine, and the acid-base balance in newborn foals. However, this delay does not significantly alter the overall process of neonatal adaptation, as indicated by metrics such as time taken to stand and suckle, heart rate, and cortisol concentration.