Failure of Passive Transfer in neonatal foals – a review.

Overview

• This article reviews the condition called Failure of Passive Transfer (FPT) in newborn foals, focusing on how it affects their health and survival by impairing their ability to receive protective antibodies from their mother’s colostrum shortly after birth.
• It discusses the physiological basis of passive immunity, risk factors for FPT, diagnostic approaches, treatment options, and preventive measures to improve the health outcomes of foals.

Introduction to Failure of Passive Transfer (FPT)

• FPT occurs when newborn foals do not receive or properly absorb sufficient immunoglobulin G (IgG) antibodies from their mother’s colostrum during the first hours after birth.
• IgG antibodies provide critical early immune protection against infections, such as diarrhea and pneumonia, which can be fatal if left unchecked.
• Because foals are born with an immature immune system and no antibody production, passive transfer from colostrum is the primary source of immune defense in early life.

Physiology of Passive Immunization in Foals

• Colostrum ingestion must occur within the first few hours of life because the foal’s intestines are only permeable to large antibody molecules for a limited time post-partum.
• Immunoglobulin G is absorbed through the intestinal lining and enters the bloodstream, providing systemic immunity.
• Absorption efficiency decreases rapidly after birth, making early nursing critical.

Risk Factors for Inadequate IgG Absorption

• Poor quality or insufficient quantity of colostrum from the mare due to age, health, or nutritional status.
• Delayed or inadequate suckling behavior by the foal, possibly from weakness or illness.
• Premature or dystocia-affected births that may impair absorption or nursing ability.
• Maternal diseases or mastitis reducing colostrum antibody levels.

Diagnostic Methods for FPT

• Assessment of IgG levels in foal serum using laboratory assays such as radial immunodiffusion or enzyme immunoassays.
• Field tests like zinc sulfate turbidity or SNAP Foal IgG test provide quick point-of-care assessment.
• Early testing, ideally within the first 12-24 hours of life, enables timely intervention.

Therapeutic Strategies

• Administration of high-quality colostrum as soon as possible after birth if initial nursing was inadequate.
• Oral supplementation with colostrum or plasma transfusion to increase circulating antibodies.
• Intravenous plasma transfusions are used if oral supplementation is too late or ineffective.

Preventive Measures and Management

• Ensuring mares have good overall health, nutrition, and vaccination status to produce high-quality colostrum.
• Monitoring foaling closely to assist with early nursing and to detect dystocia or neonatal weakness.
• Routine early screening of foal immunoglobulin status to identify FPT before clinical signs appear.
• Educating breeders and veterinarians about the critical window for passive transfer and prompt intervention protocols.

Importance and Implications

• Timely diagnosis and management of FPT significantly reduce the incidence of neonatal infections and mortality.
• Improved survival rates contribute to better long-term health and performance in horses.
• Consistent application of evidence-based practices enhances equine breeding outcomes and reduces economic losses related to foal morbidity and mortality.