Somatotropin antibody formation in cows treated with a recombinant bovine somatotropin over two lactations

Blood plasma from cows treated with somidobove, a form of recombinant bovine somatotropin, was assayed for development of antibodies against the protein. Forty-three Holstein cows, selected from an animal safety study, were monitored. Cows were divided into four groups and treated with placebo, 960, 2880, or 4800 mg somidobove per dose at 28-d intervals during two successive lactation periods. Blood plasma was collected at intervals prior to and during the lactations, and levels of IgG antibody reactive with somidobove were determined in an enzyme-linked immunosorbent assay. Virtually all of the cows treated with somidobove developed low levels (less than 40 micrograms/ml) of antibody against somidobove. One or two cows from each group responded with some-what higher levels, ranging from 40 to 200 micrograms/ml. Responses generally increased during the first 3 mo of treatment, then decreased, and remained constant with continued treatment. There was no sign of a memory response within or among the lactation periods, and no adverse health effects or decreases in lactational performance were associated with antibody production.