The Role of Oral Immunoglobulins in Systemic and Intestinal Immunity of Neonatal Calves

Neonatal dairy animals are born agammaglobulinemic and must obtain immunoglobulins (Ig) during the period of macromolecular transport within the first 24 h of life. Maternal colostrum has been the traditional source of Ig and recommendations for provision of 2 L of colostrum in two separate feedings within the first 24 h are widespread. However, stubbornly high levels of neonatal mortality and evidence of persistence of failure of passive transfer in calves indicates that too many calves consume too little Ig from colostrum or are unable to efficiently absorb IgG. Further, recent research has suggested that methods of collecting, handling and feeding of colostrum promote the transmission of biologically and economically important diseases such as Johne’s. Several approaches to improving passive transfer and reducing risk of disease transmission have been proposed, including feeding larger amounts (4 L) of colostrum at the first feeding, pasteurization of colostrum and feeding exogenous sources of Ig. Colostrum supplements and colostrum replacers are products containing <100 or ≥100 g of IgG per dose, respectively. Sources of colostrum include lacteal secretions (milk, whey or colostrum), blood and eggs (using chicken IgY). Research suggests that the efficiency of IgG absorption varies markedly by product, method of processing and source of Ig. Immunoglobulins derived from egg and supplements containing IgG from lacteal secretions are poorly absorbed by calves. Conversely, highly concentrated IgG from blood or colostrum appear to be well absorbed. More highly concentrated products (colostrum replacers) appear to have better efficiency of absorption than supplements. Immunoglobulins can also be provided to the animal following cessation of macromolecular transport (closure) as a source of local, intestinal immunity. There is firm evidence that IgG initially absorbed from colostrum into the bloodstream is resecreted into the intestinal by crypt cells. These IgG assist in reducing the incidence and severity of many different types of gastrointestinal infections, including enteropathogenic Escherichia coli, rotavirus and Cryptosporidium parvum. Sources of IgG for oral administration following closure are similar to that of colostrum supplements; however, variation in efficacy of products depending on source is different from that of colostrum supplements and replacers. Chicken egg IgY and IgG derived from colostrum and blood all appear to be effective, but degree of effectiveness depends on the specificity of Ig against specific pathogens.