Abstract

Various intravaginal progesterone-releasing devices are commercially available and each is impregnated with different amounts of progesterone. An experiment was designed to characterize plasma progesterone release profiles from Cue-Mate in comparison with other commercially available progesterone-releasing devices. Cycling, lactating Holstein cows (n = 60; BCS between 2.0 and 3.0 out of 5) from commercial dairy farms in Argentina were used in 2 replicates. All cows received 2 injections of D+ cloprostenol (PGF, Bioprost-D^®; Biotay, Buenos Aires, Argentina) 14 days apart and were randomly assigned to one of four groups to receive intravaginal devices as follows: Cue-Mate (1.56 g progesterone; Bioniche Animal Health, A/Asia Pty, Armidale, Australia; n = 10), DIB (1 g progesterone; Syntex SA, Argentina; n = 10), CIDR with 1.9 g progesterone (Pfizer Salud Animal S.A., Buenos Aires, Argentina; n = 10), or CIDR with 1.38 g progesterone (Pfizer Animal Health, Groton, CT, USA; n = 10). All devices were inserted 24 hours after the second PGF and were left in place for 31 days. Blood samples were taken for progesterone analysis at 6-hour intervals for the first 24 hours, then daily for a week, and every 2 days for an additional 25 days. Plasma progesterone concentrations were measured with a modified human double-antibody RIA kit (DPC Coat-A-Count^®; Diagnostic Products Corporation, Los Angeles, CA, USA). Cows were observed twice daily to confirm that vaginal inserts were still in place. Time-series hormone data were analyzed using the MIXED procedure for repeated measures (SAS Institute, Inc., Cary, NC, USA). Main effects of device and time, the highest mean concentration of progesterone, and the mean day on which this occurred were compared by a protected LSD test. There was no evidence of cow discomfort with any of the vaginal devices, and loss rates did not differ. There was an effect of group (P < 0.001) and day (P < 0.001) for progesterone concentrations, but there was no interaction (P = 0.89). Peak concentrations of progesterone (ng mL^-1) did not differ among groups (Cue-Mate: 5.0 ± 1.1; DIB: 3.9 ± 0.6; 1.9-g CIDR: 4.6 ± 0.6; 1.38-g CIDR: 3.7 ± 0.4; P = 0.51). Mean (± SEM) concentrations of progesterone over the 31-day insertion period differed between 1.9-g CIDR (1.8 ± 0.2 ng mL^-1) and DIB (1.5 ± 0.1 ng mL^-1, P < 0.006), with Cue-Mate (1.5 ± 0.2 ng mL^-1) and 1.38-g CIDR (1.6 ± 0.1 ng mL^-1) intermediate and not different from either. When data were evaluated from insertion until Day 7, mean plasma progesterone concentrations did not differ among groups (Cue-Mate: 2.2 ± 0.2 ng mL^-1; DIB: 2.2 ± 0.1 ng mL^-1; 1.9-g CIDR: 2.6 ± 0.2 ng mL^-1; 1.38-g CIDR: 2.1 ± 0.1 ng mL^-1). However, progesterone concentrations from insertion until Day 21 were higher (P < 0.03) in cows with a 1.9-g CIDR (2.1 ± 0.1 ng mL^-1) than in those with a DIB (1.6 ± 0.1 ng mL^-1) or a 1.38-g CIDR (1.6 ± 0.1 ng mL^-1), with Cue-Mate (1.7 ± 0.1 ng mL^-1) intermediate and not different. Based on progesterone release patterns, it was concluded that Cue-Mate intravaginal devices can be used in protocols for synchronization of estrus and ovulation as with other progesterone-releasing devices.