Four experiment stations (IL, KS, MN, and MO) conducted experiments to determine effects of introducing a CIDR (controlled internal device release) into an ovulation control program for postpartum suckled beef cows. Five hundred sixty cows were assigned randomly to two treatments: 1) 100 microg of GnRH (i.m.) followed in 7 d with 25 mg of PGF2alpha, followed in 48 h by a second injection of GnRH and one fixed-time insemination (Cosynch; n = 287) or 2) Cosynch plus one CIDR during the 7 d between the first injection of GnRH and PGF2alpha (Cosynch+P; n = 273). Cows at three stations were inseminated at the time of the second GnRH injection (n = 462), whereas 98 cows at the fourth station were inseminated 16 to 18 h after that injection. Blood samples were collected at d -17, -7, 0, and 2 relative to PGF2alpha to determine concentrations of progesterone. Ultrasonography was used to monitor follicle diameter on d 2 and to determine the presence of an embryo at 30 to 35 d after insemination. Pregnancy rates were greater (P < 0.05) for Cosynch+P- (58%) than for Cosynch-treated (48%) cows. No station x treatment interaction occurred; however, cows at MO (62%) and KS (60%) had greater (P < 0.05) pregnancy rates than those at IL (47%) and MN (44%). Cows that had follicles > 12 mm on d 2 had greater (P < 0.01) pregnancy rates than those with follicles < or = 12 mm regardless of treatment. Pregnancy rates were similar between Cosynch and Cosynch+P treatments when cycling cows had elevated concentrations of progesterone at d 0, but pregnancy rates were greater (P < 0.05) in the Cosynch+P (79%) than in the Cosynch (43%) treatment when cycling cows had low concentrations of progesterone on d 0 (at PGF2alpha injection). Similarly, among noncycling cows, pregnancy rates were greater (P < 0.05) in the Cosynch+P (59%) treatment than in the Cosynch (39%) treatment. Cows in greater body condition at the onset of the breeding season experienced improved (P < 0.001) overall pregnancy rates. Pregnancy rates for cows that calved > 50 d before the onset of the breeding season were greater (P < 0.01) than those for cows that calved < or = 50 d. Thus, treatment of suckled cows with Cosynch yielded acceptable pregnancy rates, but addition of a CIDR improved pregnancy rates in noncycling cows. Body condition and days postpartum at initiation of the breeding season affected overall efficacy of the Cosynch and Cosynch+P protocols.

Ovarian cysts in dairy cattle are generally defined as follicular structures of at least 2.5 cm in diameter that persist for at least 10 d in the absence of a corpus luteum. The incidence of ovarian cysts has been reported to be from 6 to 19% and, therefore, cystic ovarian disease is a serious cause of reproductive failure in dairy cattle. There have been several different hypotheses about the cause of ovarian cysts. After monitoring postpartum cows that spontaneously developed ovarian cysts and postpartum cows with or without ovarian cysts administered estradiol benzoate, the authors have suggested that postpartum ovarian cysts developed when the hypothalamus and pituitary appeared to be less responsive in releasing luteinizing hormone (LH) under the influence of estradiol. Spontaneous reestablishment of ovarian cycles occurred in about 60% of the cows that developed ovarian cysts before the first postpartum ovulation. In contrast, only about 20% of the cows that developed ovarian cysts after the first postpartum ovulation spontaneously reestablished ovarian cycles. The authors have also reported that even if ovarian cycles are not reestablished, ovarian cysts may regress, but only in the presence of follicular development, which subsequently develops into ovarian cysts. Investigators have shown that 40 to 80% of the cows with ovarian cysts reestablished ovarian cycles following treatment with products high in LH activity. Gonadotropin releasing hormone (GnRH), which stimulates reestablishment of ovarian cysts in about 80% of the cows treated, has more recently been recommended as a treatment for ovarian cysts. The GnRH-induced LH surge appears to stimulate luteinization of the ovarian cyst wall. Cows then exhibit estrus about 21 d following GnRH treatment. The conception rate at the first estrus after GnRH treatment has been reported to be 40 to 50%. The interval from GnRH treatment to estrus has been reduced by administering prostaglandin F2 alpha (PGF2 alpha) 9 d after GnRH. The PGF2 alpha appears to regress the luteinized ovarian cysts and cows exhibit estrus 2 to 3 d after PGF2 alpha treatment (11 to 12 d after GnRH). Gonadotropin releasing hormone has also been used to reduce the incidence of ovarian cysts in postpartum cows. To be effective in reducing the incidence of ovarian cysts, GnRH should be administered about 2 wk postpartum. However, cows may have a predisposition for cystic ovarian disease and treatments, therefore, are only temporary solutions. A better alternative would probably be to select against ovarian cysts.

Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48 h after PGF(2alpha), followed by one fixed-time AI (TAI) 16 to 20 h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF(2alpha) injection (1 to 2 h after CIDR insert removal), and 48 h after the PGF(2alpha) injection to determine cyclicity status before initiation of treatment, luteal status at the PGF(2alpha) injection, and incidence of luteal regression. Overall, conception rates at 28 (40 vs. 50%) and 56 d (33 vs. 38%) after TAI differed between OVS and OVS + CIDR, respectively; but a treatment x location interaction was detected. Compared with OVS, pregnancy outcomes were more positive for OVS + CIDR cows at 4 of 6 locations 28 d after TAI and at 3 of 6 locations 56 d after TAI. An interaction of luteal status (high vs. low) before CIDR insert removal and PGF(2alpha) injection with pretreatment cycling status indicated that cows having low P4 at PGF(2alpha) injection benefited most from P4 supplementation (OVS + CIDR = 36% vs. OVS = 18%), regardless of pretreatment cycling status. Pregnancy loss between 28 and 56 d after TAI was greater for noncycling cows (31%) compared with cycling cows (16%). Pregnancy loss for cows receiving P4 (21%) did not differ from that for cows not receiving P4 (21%). Supplementation of P4, pretreatment cycling status, and luteal status before PGF(2alpha) injection altered follicular diameters at the time of the second GnRH injection, but were unrelated to pregnancy outcomes. Incidence of multiple ovulation was greater in noncycling than in cycling cows. Further, cows having multiple ovulations had improved pregnancy outcomes at 28 and 56 d after TAI. In summary, a CIDR insert during the Ovsynch protocol increased fertility in lactating cows having low serum P4 before PGF(2alpha) injection. Improved pregnancy outcomes were observed at some, but not all locations.