Periparturient dairy cows experience impaired immune function, exhibited as a transient decrease in neutrophil function. This decrease in immune competence is associated with an increase in susceptibility to
bacterial infections, including
mastitis and metritis. Bovine
granulocyte colony stimulating factor (bG-CSF) is an endogenous
protein that enhances neutrophil bactericidal functions and increases the production of neutrophils from bone marrow precursors. Administration of
pegbovigrastim (recombinant bG-CSF covalently bound to
polyethylene glycol) around the time of calving has been shown to reduce the incidence of new clinical
mastitis cases in a natural disease model system. To further explore the application of
pegbovigrastim under herd management systems typical of those found in the US dairy industry, we conducted a multicenter field study to evaluate the efficacy and clinical safety of
pegbovigrastim administered to multiparous cows and heifers approximately 7 d before calving and within 24 h of calving. Responses of treated cows were compared with those of animals treated with sterile saline. Animals treated with
pegbovigrastim exhibited 4- to 5-fold increases in circulating neutrophil numbers within 24 h of treatment initiation, and this increase persisted at least a week beyond the second dose.
Pegbovigrastim-treated animals exhibited a 35% decrease in the incidence of clinical
mastitis relative to the controls during the first 30 d of lactation. Animals treated with
pegbovigrastim also exhibited a 52% reduction in failure to return to visual estrus within 80 d of calving. We observed no differences in somatic cell count or milk composition between treated and control animals. We also found no differences in the duration of pregnancy or proportion of viable calves in treated cows relative to control animals. These results indicate that administration of
pegbovigrastim provides a well-tolerated, novel approach to overcoming periparturient immune suppression, resulting in reduced susceptibility to clinical
mastitis during early lactation.