Passive Immunity Establishment Through Colostral IgG Absorption in Neonatal Ruminants: Foundation for Efficient Ruminant Production.

Passive immunity, the acquisition of specific immune protection through external antibodies or immune components, is critically important for neonatal survival. In ruminants, however, neonatal hypogammaglobulinemia, a consequence of their epitheliochorial placental structure preventing prenatal antibody transfer, often leads to high morbidity and mortality. Consequently, neonatal ruminants are entirely dependent on the timely consumption of colostrum to acquire sufficient immunoglobulin G (IgG) for protection. Establishing robust passive immunity is therefore a cornerstone for their survival, healthy development, and future production efficiency. This review synthesizes current knowledge on the establishment of passive immunity in neonatal ruminants. We first outline the fundamental principles of passive immunity transfer, then delve into the specific pathways and molecular mechanisms in ruminants. Key factors influencing this process are subsequently discussed. Furthermore, we highlight the long-term impact of passive immunity on adult production performance. This review aims to provide a scientific foundation for optimizing colostrum management strategies and to stimulate future research into the intricate mechanisms of IgG absorption.