Abstract
Objective was to compare serum concentrations of progesterone (P4) in ovariectomized cows receiving new, re-used disinfected, and re-used autoclaved controlled internal drug release (CIDR) inserts. Five ovariectomized (OVX) Brahman x Hereford (F1) cows and one OVX Hereford cow were used in a replicated 3 x 3 Latin square design.. Each experimental period was 7 days, with at least 48 h between periods. Treatments were 1) New, 2) Re-used disinfected (DIS), and 3) Re-used autoclaved (AC). All re-used CIDRs had been inserted previously in beef cows for 7 days. Upon removal, DIS CIDRs were washed thoroughly and soaked in a chlorhexidine gluconate solution (0.03%) for 2 h, rinsed thoroughly with water and air-dried. For the AC treatment, CIDRs were not soaked in disinfectant but were autoclaved at 121°C and 724 mm Hg for 20 min before use. Blood samples were collected at 0, 10, 30, 60, 180, and 480 min relative to time of insertion of CIDRs, daily until day 7, and at 30, 60, and 180 min relative to time of removal for RIA of P4. Mean serum concentrations (ng/mL) of P4 during the 7-day period of insertion were greater (P < 0.03) for New (3.7 ± 0.2) and AC (3.4 ± 0.3) than for DIS CIDRs (2.8 ± 0.2). These effects were created primarily by differences occurring during the first 8 h after CIDR insertion. Within this interval, mean concentrations differed (P < 0.05) among all treatments. Cows bearing DIS CIDRs had a smaller (P < 0.05) area under the curve (AUC) during the first 4 days after insertion compared to New or AC CIDRs. Autoclaved CIDRs had a greater AUC compared to New and DIS during interval from CIDR insertion (0 h) to 8, 24 and 48 h. Autoclaving may be the best option when re-using CIDR inserts because it creates greater concentrations of P4 immediately after insertion and reduces maximally the risk of disease transmission.