Effect of intrauterine antimicrobial treatment in reducing calving-to-conception interval in cows with endometritis

A prospective clinical trial was conducted on 2 large dairies in the San Joaquin Valley of California to determine whether a single intrauterine infusion with procaine penicillin G or oxytetracycline reduced the calving-to-conception interval in cows with endometritis. Cows with endometritis were randomly assigned to a treatment or a control group. The uterus of treated cows on 1 dairy was infused with 0.8 to 1.0 million U of procaine penicillin G in 40 ml of sterile water, and the uterus of treated cows on the other dairy was infused with 500 mg of oxytetracycline in 20 ml of sterile water, both of which were typical doses used on dairies in the area. A difference was not observed in the cumulative proportion of cows remaining nonpregnant between 87 penicillin-treated and 77 control cows on the 1 dairy (P = 0.356), or between 74 oxytetracycline-treated and 62 control cows on the other dairy (P = 0.174). Results suggest that routine infusion of antibiotics to treat endometritis, as commonly practiced, may not be efficacious.