Changes in immunoglobulin levels in whey during experimental Streptococcus agalactiae mastitis.

Total protein and immunoglobulin levels in the wheys of eight first lactation heifers, four vaccinated and four unvaccinated, were measured during three consecutive experimental intramammary infections with Streptococcus agalactiae. There were no significant differences between infections 1, 2 and 3 in the protein or immunoglobulin content of the uninfected quarters. Peak whey total protein of the infected quarters came earlier with each infection, until by the third they were seen after eight hours. During this acute phase a reversal of the normal milk IgG1/IgG2 ratio in all infected quarters was measured. Increases in whey IgA and IgM in the infected quarters of the vaccinates were also noted. A similar response only occurred following the third infection of the unvaccinated animals. All whey immunoglobulin levels returned to normal by 48 hours after infection, after which only IgG1 levels increased in infected quarters.