Insemination timing affects pregnancy rates in beef cows treated with CO-Synch protocol including an intravaginal progesterone insert.

Our objective was to determine the optimal time to artificially inseminate lactating beef cows (Bos taurus typicus) after using the standard CO-Synch protocol that also included a progesterone-releasing, intravaginal controlled internal drug release (CIDR) insert. Cows (N=605) at three locations were inseminated at four different times after CIDR insert removal and the prostaglandin F(2alpha) administration of the CO-Synch+CIDR protocol: 48, 56, 64, or 72h. Blood samples were collected 9 to 10 d before and on the day of CIDR insertion.

Detection of anovulation by heatmount detectors and transrectal ultrasonography before treatment with progesterone in a timed insemination protocol.

Our objective was to determine the accuracy of identifying noncycling lactating dairy cows before the application of a timed artificial insemination (AI) protocol [with or without progesterone supplementation via a controlled internal drug-release (CIDR) insert and 2 different timings of AI] by using heatmount detectors and a single ovarian ultrasound examination. At 6 locations in the Midwest, 1,072 cows were enrolled in a Presynch protocol (2 injections of PGF(2alpha) 14 d apart), with the second injection administered 14 d before initiating the Ovsynch protocol (injection of GnRH 7 d before and 48 h after PGF(2alpha) injection, with timed AI at 0 or 24 h after the second GnRH injection). Heatmount detectors were applied to cows just before the first Presynch injection, assessed 14 d later at the second Presynch injection (replaced when activated or missing), and reassessed at initiation of the Ovsynch protocol.

Factors influencing upfront single-and multiple-ovulation incidence, progesterone, and luteolysis before a timed insemination resynchronization protocol.

Our objectives were to determine relationships among factors influencing responses to the first GnRH injection in a timed artificial insemination (TAI) protocol and subsequent fertility after altering timing of the second GnRH injection and AI relative to PGF(2alpha) injection. Replacement heifers (n = 86) and 613 lactating cows previously inseminated were diagnosed not pregnant to form 77 breeding clusters spanning 36 mo. At not-pregnant diagnosis (d 0), females received 100 mug of GnRH, and then 7 d later, they received 25 mg of PGF(2alpha).

Ovarian traits after gonadotropin-releasing hormone-induced ovulation and subsequent delay of induced luteolysis in an Ovsynch protocol.

Our objective was to determine whether delaying the PGF2alpha injection by 24 or 48 h after the first GnRH injection in an Ovsynch protocol (from a standard 7 d) altered ovarian characteristics in lactating dairy cows. Beginning 9 d after removal of a progesterone-releasing controlled internal drug release (CIDR) insert and injection of PGF2alpha (d 6.4 of the estrous cycle), 36 Holsteins (average body weight = 707 +/- 12 kg and body condition score = 2.

Interventions after artificial insemination: conception rates, pregnancy survival, and ovarian responses to gonadotropin-releasing hormone, human chorionic gonadotropin, and progesterone.

We hypothesized that increasing concentrations of progesterone (P4) after artificial insemination would increase fertility. Our objective was to assess changes in ovarian structures, incidence of ovulation, and change in serum P4 in response to GnRH, human chorionic gonadotropin (hCG), or exogenous P4 (controlled internal drug release; CIDR insert) treatment beginning 4 to 9 d after artificial insemination (d 0) and again 7 d later (experiment 1). Blood was collected from 753 cows in 3 herds on d 0 and 7.