Cows enrolled in a pilot randomized clinical trial evaluating pegbovigrastim administered to dairy cows at dry-off had reduced incidence of intramammary infection.

Objective: The objective of this pilot study was to determine if an alternative dosing schedule of pegbovigrastim (PEG; Imrestor; Elanco Animal Health) affects mammary gland health, rear udder width, or milk production of healthy dairy cows.

Animals: 20 pregnant late-lactation Holstein cows in November 2019 through April 2020.

Procedures: Cows were randomly assigned to receive subcutaneous injections with either 15 mg of PEG (PEG group; n = 10) or a sham injection with saline (0.9% NaCl) solution (control group; 10) administered 7 days before dry-off and at dry-off. Quarter milk samples were collected for bacterial culture and somatic cells before and after dry-off and after calving. Mammary gland width was assessed before and after dry-off. Daily milk yields were evaluated after calving.

Results: The incidence of intramammary infection was 5 times greater for quarters of cows in the control group than for quarters of cows that received PEG. The effect of treatment on somatic cell count was not significant, but the effects of period and a treatment-by-period interaction were identified. Treatment did not significantly affect milk production in the subsequent lactation, but the effects of period and an interaction of treatment by period were identified. Rear udder width after dry-off was not significantly affected by treatment, but an effect of period was identified.

Clinical Relevance: In this pilot study, cows treated with PEG using an alternative dosing schedule had reduced incidence of intramammary infection and an interaction of treatment by sampling period was observed for milk yield. These results suggest that further studies with larger numbers of cows are warranted.