The transfer of passive immunity to the foal and its relation to immune status after birth.

This study examines the process of passing immunity from a mother horse (mare) to its newborn foal, its efficiency right after birth and how it evolves as the foal ages, especially during the first six months of life.

Objective of the Research

• The primary objective of this research is to understand the mechanism of the transfer of maternal immunity to the foal and its subsequent impact on the foal’s immune system after birth.

Mechanism of Immunity Transfer

• The study reviews the complex interplay between the mare’s immune system and the newborn foal’s physiology. It underlines the fact that specialized cells in the small intestine of the newborn are crucial for this process as they have the maximum ability to absorb macromolecules (large molecules typically formed by polymerization).
• These are eventually replaced by mature cells, which have a reduced capacity for such absorption. This process follows a linear decline whereby absorption capability decreases continuously and stops completely within 24 hours after birth.

The First Six Months of the Foal’s Life

• The research goes on to evaluate the changes in the immune system of the foal over the next six months. It shows that the levels of passively acquired antibodies fall rapidly during the first four weeks.
• The drop is so significant that by the end of this period, the levels are usually less than half of their initial values, and by the time the foal is six months old, the passively acquired antibodies have generally completely disappeared.
• Despite this rapid decrease in maternal antibodies, the study highlights that the foal shows immunological competence or the ability to trigger an immune response soon after birth. This is important as it enables the foal to fight off infections and diseases.

Development of Autogenous Immunoglobulins

• Interestingly, the study points out that while the newborn foal can react to infections, it does not produce any significant levels of its own immunoglobulins (antibodies produced by the immune system to fight off infections) until it is between two to three months old, thus emphasizing the importance of the passive immunity obtained from the mother.