A cohort of 125 cows (Zebu-Holstein crosses) were screened every two months during a period of two years for IgG antibodies to 20 viral, bacterial, rickettsial and parasitic agents. The screening was performed on sera using the ELISA procedure. The IgG levels fluctuated during pregnancy in a regular and similar way for all the antigens tested. IgG reached its lowest levels in the fourth and seventh month of pregnancy, a significant increase ocurred during the last month of pregnancy and this was followed by a precipitous decline during the first month post partum. The IgG fluctuations associated with the different phases of reproductive status may interact with seasonal changes in IgG levels. The changes in IgG levels during pregnancy may have the result that an individual animal oscillates between being seropositive and seronegative. This can have an important impact on serological studies of abortion epidemiology.
cohort; serological screening; pregnancy
