Immunocrit in neonatal piglets: Importance and influencing factors through the eyes of a practitioner

This review critically reflects on the use of immunocrit in neonatal piglets as an indicator of passive immunity status. Under intensive production conditions and with the development of hyperprolific sow lines, reliable techniques are required to objectively assess the success of passive immunity transfer to the piglets. The immunocrit is a cost-effective indirect method for assessing immunoglobulin concentration in serum or plasma samples obtained 12-48 h after the birth of the first piglet, by using the principle of protein precipitation. Reduced growth performance, delayed development, greater vulnerability to illness, and higher pre-weaning mortality are all consistently associated with low immunocrit readings. Higher numbers, on the other hand, indicate effective immunoglobulin absorption and better long-term productivity. Various management strategies, including split suckling, cross-fostering, and farrowing system design, directly influence immunocrit values by affecting colostrum intake and competition among piglets. Certain interventions, such as oxytocin administration or anti-inflammatory treatments, may influence colostrum composition or farrowing conditions, but they do not always result in appreciable changes in immunocrit levels. Its usefulness, quickness, and field application make it an important tool in contemporary swine production, even though it lacks the analytical precision of enzyme-linked immunosorbent assay and radial immunodiffusion that quantify individual immunoglobulin isotypes, such immunoglobulin G. For herd level interpretations the immunocrit results should be complementary to the evaluation of the farrowing and colostrum management practices, the sow diet and the handling of the piglets in supporting corrective measures prenatally.