Increase of serum gamma-glutamyltransferase in neonatal Standardbred foals.

The study was conducted to analyze the level of a certain enzyme, gamma-glutamyltransferase (GGT), and its changes in newborn Standardbred foals from birth to day 28. Researchers found that GGT levels in foals did not significantly change over this period and were consistently higher than in mares, suggesting that the increased GGT came from an internal (endogenous) source, not from the mare’s first milk (colostrum).

Study Design and Analysis

• The researchers collected serial blood samples from 16 newborn Standardbred foals from the moment of birth until the 28th day after birth.
• The joined component, or serum, from these samples were analyzed for three substances—gamma-glutamyltransferase (GGT), aspartate transaminase, and immunoglobulin G (IgG).
• The colostrum—first milk produced by the mares—of the respective foals was also tested for GGT activity.

Findings

• The scientists found that the average serum aspartate transaminase activities were notably increased by postpartum hour 48 and continued to increase gradually over the first 14 days.
• The average serum IgG concentrations, which offer protection from infection to the foals in their early life, were significantly higher than the values before the foal consumed colostrum, as early as 5 hours after the foals first suckled. This increased IgG concentration lasted throughout the 28-day sampling period.

Serum GGT Activity Analysis

• Serum GGT activity did not show a significant change over the period sampled. However, it did vary considerably from one foal to another.
• The level of GGT in the blood of the foals was notably higher than that in the mares throughout the study.
• The pattern of GGT activity over time did not show any clear trend or pattern of change in each foal. This suggests that the increased serum GGT activity in foals is not linked to the intake of colostrum.
• The researchers found no correlation between serum GGT activities and IgG concentrations 24 hours after the foals first suckled.

Implications of the Findings

• The researchers did not find any evidence to suggest that the increase of serum GGT activity in foals comes from the colostrum of the mares, contradicting some previous assumptions.
• The study suggests that the increased GGT activity in the serum of foals is due to endogenous (internal) sources within the foal itself, rather than external influences or intakes. This finding requires further investigation and could have implications for the understanding of foal health and development.