Efficiency of Previously used CIDR Stored for a Prolonged Period

| This study investigated the efficiency of the previously used controlled internal drug release (CIDR) stored for 30 days before reusing. In the first experiment, twenty seven Holstein cows at the day of estrus (day 0) received either no treatment (control), new or reused CIDR and blood samples were collected at day 0, 1, 3 and 7. At day 1 and 3, serum progesterone concentration in cows received new CIDR (1.417 and 1.616 ng/ml) was significantly higher than in cows received a reused one (0.545 and 0.954 ng/ml) which in turn was higher than the control group. In the second experiment, estrous cycle was synchronized using Ovsynch, New-CIDRsynch or Reused-CIDRsynch. Cows in Ovsynch (n=119) received GnRH on day 0 then PGF2α on day 7. Fifty six hours after the PGF2α cows received another dose from GnRH and inseminated 18 h latter. Cows in new-CIDRsynch (n=870) and reused-CIDRsynch (n=220) were treated in the same way with exception of inserting a new or reused CIDR between day 0 and day 7. Non returned cows were examined for pregnancy diagnosis at 30 and 70 days post-insemination. Pregnancy-30 and 70 rates after New-CIDRsynch (36.1% and 30.5%) and Reused-CIDRsynch (36.4% and 31.8%) tended to be higher than after Ovsynch (27.7% and 25.2%) (P= 0.07: 0.08). In conclusion, the previously used CIDR -stored for 30 dayshave residual progesterone and incorporating new or reused CIDR into Ovsynch improved the efficiency of the protocol in a similar way.