A Method for Measuring Specific Antibodies in Bovine Lacteal Secretions During the Nonlactating Period

¹ Livestock and Poultry Sciences Institute, Agricultural Research Service, USDA, Beltsville, MD 20705
² Department of Animal Sciences, University of Maryland, College Park 20742

A large portion of new IMI in dairy cattle occurs during the nonlactating period. Because antibiotic infusions at the beginning of the nonlactating period are only partially effective, attempts have been made to stimulate the production of protective antibodies in lacteal secretions during this period. However, measurement of antibodies in mammary secretions during the nonlactating period has been hampered by the complex, viscous nature of these secretions. This report describes the use of caprylic acid to clarify secretions from the bovine mammary gland during the nonlactating period to provide a more accurate measurement of specific antibody. Six healthy Jersey cows were injected in the area of the supramammary lymph node with an encapsulated strain of Staphylococcus aureus in dextran sulfate at the beginning of the nonlactating period and 15 and 30 d later. Seven healthy unimmunized Jersey cows served as controls. Lacteal secretions taken at the beginning of the nonlactating period; at 15, 30, and 45 d into the nonlactating period; and at calving were treated with caprylic acid prior to assay for specific antibodies using ELISA. Purified S. aureus capsule was used as the antigen in the ELISA. Caprylic acid lowered non-specific binding of IgG₁ and IgM in secretions during the dry period from unimmunized control cows and lowered IgM from immunized cows. The most pronounced effect of caprylic acid was an increase in IgG₂ binding in secretions from immunized cows. Treatment with caprylic acid more accurately measured specific activity of Ig in mammary secretions during the nonlactating period.

Key Words: dry period • isotype • antibody • lacteal secretions

Submitted on January 27, 1995
Accepted on February 12, 1996