Reusing progesterone devices in Bos taurus beef cows: effects on circulating progesterone and fertility variables after a 7-day synchronization protocol and timed artificial insemination.

This study evaluated how many times progesterone (P4)-releasing intravaginal devices (CIDRs; 1.38 g P4) could be reused in a 7-day CO-Synch + CIDR protocol for Bos taurus cattle. In Experiment 1, heifers (n = 21) without a corpus luteum were assigned treatments lasting 7 days: New CIDR, CIDR used 1, 2 or 3 times (CIDR1, CIDR2, and CIDR3, respectively) and disinfected with chlorhexidine, or autoclaved (A-CIDR1, A-CIDR2, and A-CIDR3 respectively). Circulating P4 concentrations were measured for 7 days. Autoclaving CIDRs did not affect circulating P4 concentrations during the insertion period (P > 0.1). On the last day of the 7-day period, all treatment groups had a mean concentration of P4 above 1 ng/mL. In Experiment 2, lactating multiparous and primiparous cows were submitted to a 7-day CO-Synch + CIDR protocol followed by timed artificial insemination (TAI; Day 0 [D0]). Cows were submitted to the following treatments: new CIDR (CIDR0; n = 319), A-CIDR1 (n = 309), A-CIDR2 (n = 304), and A-CIDR3 (n = 306). The number of CIDR uses reduced the circulating P4 concentrations (P = 0.0041) and increased the largest follicle diameter (P = 0.055) on D-3 but did not affect proestrus length or estrous expression. The number of CIDR uses did not affect pregnancy/AI in multiparous cows, but A-CIDR3 reduced pregnancy/AI by 46.2% in primiparous cows. There is a chance that used CIDRS inducing follicular persistency and reducing fertility. Our observations suggest that CIDRs can be reused up to 3 times in multiparous cows, but only up to 2 times in primiparous.