Estrous synchronization using an intravaginal progesterone device in combination with gnrh or estradiol benzoate characterized by the initial ovarian conditions in Japanese black cows

Estrous synchronization using a Controlled Internal Drug Releasing device (CIDR) in combination with GnRH or estradiol benzoate (EB) treatment was investigated in Japanese black cows characterized with initial ovarian conditions. A total of 142 cows were allocated to one of four treatments: insertion of CIDR for eight days (Group A: n=34), CIDR with 100 microg of GnRH on d 0 (Group B: n=54, d 0=CIDR insertion), CIDR with GnRH on d 0 and 1 mg of EB on d 10 (Group C: n=20) or CIDR with 2 mg of EB on d 0 and 1 mg of EB on d 9 (Group D: n=34). All cows received 25 mg of PGF(2alpha) on d 7 and blood was collected for progesterone (P4) analysis on d 0, 8, and 21. AI was performed at estrus, but in Group D timed AI was set following a day of EB treatment. Estrus was induced in 141/142 cows, and the majority of which occurred on d 10 and 11 (98 cows, 34 cows). GnRH treatment induced more intermediate ovulation than EB treatment in cows with CL on d 0 (19.0% vs. 0%). Ovulation after CIDR removal was significantly higher in cows with CL on d 0 compared to those without CL (87.0% vs. 71.4%). Group B showed higher conception rates than those combined with Groups C and D where EB was injected after CIDR removal (51.1% vs. 38.9%). Conception had no correlation with either CL existence on d 0 or intermediate ovulation on d 8. P4 concentrations on d 8 were significantly lower compared to those on d 0 or d 21. On d 21 in cows without intermediate ovulation, Group A showed significantly lower P4 concentrations than the other 3 groups. The data suggests that CIDR insertion with PGF(2alpha) treatment is an effective method for estrous synchronization irrespective of initial ovarian conditions, and GnRH treatment at CIDR insertion induces intermediate ovulation and improves the conception rate in Japanese black cows.     

GnRH treatment at CIDR insertion influences ovarian follicular dynamics in Japanese black cows

Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F2alpha (PGF2alpha) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 +/- 1.6 ng/ml) was significantly higher than those in Group B (4.1 +/- 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 +/- 12.0 hr and 76.0 +/- 6.9 hr in three cows in Group A, and 75.0 +/- 15.1 hr and 93.0 +/- 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.     

Ovsynch plus CIDR protocol for timed embryo transfer in suckled postpartum Japanese Black beef cows

We compared synchronization and pregnancy rates, and the increase in blood progesterone concentrations during luteal development, between (1) Ovsynch plus an intravaginal controlled internal drug release (CIDR) device protocol followed by timed embryo transfer (timed ET), and (2) a conventional estrus synchronization method using PGF(2 alpha) and ET in suckled postpartum Japanese Black beef cows. Cows in the PGF group (n=18) received a PGF(2 alpha) analogue when a CL was first palpated per rectum at 10-d intervals after 1 to 2 month postpartum. Cows (n=11), which showed estrus (Day 0) within 5 d of the PGF(2 alpha), and had a CL on Day 7, received ET. Cows in the Ovsynch+CIDR group (n=19) underwent the Ovsynch protocol plus a CIDR for 7 d (GnRH analogue and CIDR on Day-9, PGF(2alpha) analogue with CIDR removal on Day-2, and GnRH analogue on Day 0), with ET on Day 7. The ovulation synchronization (100%) and embryo transfer (100%) rates in the Ovsynch+CIDR group were greater (P<0.01) than the estrus synchronization (66.7%) and the embryo transfer (61.1%) rates in the PGF group. The postpartum interval at ET in the Ovsynch+CIDR group (62.5 +/- 2.5 d) was shorter (P<0.01) than in the PGF group (74.9 +/- 3.9 d). The pregnancy rate in the Ovsynch+CIDR group (57.9%) did not differ significantly from that in the PGF group (50.0%). Plasma progesterone concentrations were not significantly different in the two groups on Days 0, 1, 2, 5, 7, 14 and 21. In summary, higher synchronization and transfer rates, and shorter postpartum interval to ET, can be achieved with timed ET following the Ovsynch plus CIDR protocol than after estrus with the single PGF(2 alpha) treatment followed by ET in suckled postpartum recipient beef cows. Pregnancy rates were similar. Also, the increase in blood progesterone concentrations during luteal development following ovulation synchronized by the Ovsynch plus CIDR protocol was similar to that after estrus induced by the PGF(2 alpha) treatment.     

Inhibitory effects of CIDR-based ovulation-synchronization protocols on uterine PGF2alpha secretion at the following luteal phase in early postpartum non-cycling beef cows

We investigated whether CIDR-based ovulation-synchronization protocols inhibit secretion of prostaglandin (PG) F2alpha from the uterus in the following luteal phase in non-cycling beef cows. Ten early (a month) postpartum non-cycling Japanese Black beef cows were treated with (1) Ovsynch (GnRH analogue on Day 0, PGF2alpha analogue on Day 7, and GnRH analogue on Day 9; n=3), (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from Day 0; n=4), or (3) estradiol benzoate (EB) Ovsynch+CIDR (EB on Day 0 in lieu of the first GnRH treatment followed by the Ovsynch+CIDR protocol; n=3). An oxytocin challenge was administered on Day 24 to examine uterine PGF2alpha secretion. Plasma concentrations of 13,14-dihydro-15-keto- PGF2alpha were lower at 30-120 min after oxytocin administration in the Ovsynch+CIDR group and 75 min after administration in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). Plasma progesterone concentrations were higher from Days 1 to 7 in the Ovsynch+CIDR group and from Days 1 to 5 in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). The progesterone concentrations were higher on Days 27 and 29 in both CIDR-treated groups than in the Ovsynch group (P<0.05). In conclusion, in non-cycling beef cows, CIDR-based ovulation-synchronization protocols inhibit uterine PGF2alpha secretion in the following luteal phase and prevent premature luteolysis as is seen with the Ovsynch protocol.     

Reproductive performance of dairy cows not detected in oestrus but with a detectable corpus luteum, in response to treatment with progesterone, oestradiol benzoate and prostaglandin F2alpha

AIM: To determine if the reproductive performance of dairy cows not previously detected in oestrus but with a detectable corpus luteum before the planned start of mating (PSM), could be improved by treatment with progesterone, oestradiol benzoate (ODB) and prostaglandin F2alpha (PGF). METHODS: Cows in 18 herds which had not been detected in oestrus, but which had a detectable corpus luteum present at veterinary examination 7 days prior to the PSM (Day -7), were allocated to 1 of 2 groups. Treated cows (n=232) received an injection of 2 mg ODB and an intravaginal progesterone releasing device (CIDR insert) on Day -7, and an injection of PGF on the day of insert removal 7 days later (Treated group). The Control group (n=243) remained untreated. Cows were mated to detected oestrus from Day 0, and conception dates confirmed by manual palpation or transrectal ultrasonography. RESULTS: During the first 7 days of mating, 37.4% of Control cows and 65.9% of Treated cows were inseminated on detection of oestrus (p<0.001). Pregnancy rates for this period were 20.4% and 36.3%, respectively (p=0.001). Conception rates to first insemination, pregnancy rates after 21 days of mating and at the end of the mating period were similar between groups (p>0.1). Median interval from the PSM to conception did not differ between treatment groups (24 and 23 days for Control and Treated, respectively, p>0.1). CONCLUSION: Treating postpartum dairy cows which had not previously been detected in oestrus but which had a detectable corpus luteum, with progesterone, ODB and PGF did not significantly improve their reproductive performance compared with no hormonal intervention. KEY WORDS: dairy cattle, postpartum, anoestrous, reproduction, progesterone treatment.     

Influence of a controlled internal drug release after fixed-time artificial insemination on pregnancy rates and returns to estrus of nonpregnant cows

We determined whether an ovulatory estrus could be resynchronized in previously synchronized, AI nonpregnant cows without compromising pregnancy from the previous synchronized ovulation or to those inseminated at the resynchronized estrus. Ovulation was synchronized in 937 suckled beef cows at 6 locations using a CO-Synch + progesterone insert (controlled internal drug release; CIDR) protocol [a 100-microg injection of GnRH at the time of progesterone insert, followed in 7 d by a 25-mg injection of PGF(2alpha) at insert removal; at 60 h after PGF(2alpha), cows received a fixed-time AI (TAI) plus a second injection of GnRH]. After initial TAI, the cows were assigned randomly to 1 of 4 treatments: 1) untreated (control; n = 237); 2) progesterone insert at 5 d after TAI and removed 14 d after TAI (CIDR5-14; n = 234); 3) progesterone insert placed at 14 d after TAI and removed 21 d after TAI (CIDR14-21; n = 232); or 4) progesterone insert at 5 d after TAI and removed 14 d after TAI and then a new CIDR inserted at 14 d and removed 21 d after TAI (CIDR5-21; n = 234). After TAI, cows were observed twice daily until 25 d after TAI for estrus and inseminated according to the AM-PM rule. Pregnancy was determined at 30 and 60 d after TAI to determine conception to the first and second AI. Pregnancy rates to TAI were similar for control (55%), CIDR5-14 (53%), CIDR14-21 (48%), and CIDR5-21 (53%). A greater (P < 0.05) proportion of nonpregnant cows was detected in estrus in the CIDR5-21 (76/110, 69%) and CIDR14-21 (77/120, 64%) treatments than in controls (44/106, 42%) and CIDR5-14 (39/109, 36%) cows. Although overall pregnancy rates after second AI service were similar, combined conception rates of treatments without a CIDR from d 14 to 21 [68.7% (57/83); control and CIDR5-14 treatments] were greater (P = 0.03) than those with a CIDR during that same interval [53.5% (82/153); CIDR5-21 and CIDR14-21 treatments]. We conclude that placement of a progesterone insert 5 d after a TAI did not compromise or enhance pregnancy rates to TAI; however, conception rates of nonpregnant cows inseminated after a detected estrus were compromised when resynchronized with a CIDR from d 5 or 14 until 21 d after TAI.     

Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F2alpha

Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F(2alpha) (PGF(2alpha)) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d -7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF(2alpha); control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF(2alpha) increased (P < 0.05) the number of mounts received (22.5 +/- 3.0 vs. 13.7 +/- 3.9 for CIDR-PGF(2alpha) vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF(2alpha) (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF(2alpha) than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF(2alpha) decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 +/- 1.1 vs. 9.0 +/- 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF(2alpha)-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF(2alpha) at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.     

Ovarian and endocrine responses associated with the treatment of cystic ovarian follicles in dairy cows with gonadotropin releasing hormone and prostaglandin F2alpha, with or without exogenous progesterone

The objectives of this observational study were to document ovarian and endocrine responses associated with the treatment of cystic ovarian follicles (COFs) in dairy cows, using gonadotropin releasing hormone (GnRH) and prostaglandin F2alpha (PGF) with or without exogenous progesterone. A secondary objective was to determine pregnancy establishment following synchronization of ovulation and timed insemination in cows diagnosed with COFs. In trial I, 18 Holstein cows diagnosed with COFs received 2 injections of 100 microg GnRH, 9 d apart, with 25 mg PGF given 7 d after the 1st GnRH. A new follicle developed in all 18 cows after the 1st GnRH, and 83% of cows ovulated following the 2nd GnRH. Cows were inseminated 16 h after the 2nd GnRH. Of the 17 cows available for pregnancy diagnosis, 7 were confirmed pregnant. In trial II, 8 cows with COFs received GnRH and an intravaginal progesterone device (CIDR) concurrently, then PGF 7 d later. The CIDR was removed 2 d after PGF administration. Plasma estradiol concentrations declined following CIDR insertion. In all cows, a new follicle developed following GnRH treatment; estradiol-surge and estrus occurred spontaneously after CIDR-removal. Seven of 8 cows ovulated the new follicle. In dairy cows diagnosed with COFs, treatment with GnRH followed by PGF 7 d later, with or without exogenous progesterone, resulted in the recruitment of a healthy new follicle; synchronization of ovulation and timed insemination resulted in a 41% pregnancy rate.     

Efficacy of an intravaginal progesterone insert and an injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in postpartum beef cows, peripubertal beef heifers, and dairy heifers

The objective was to test the efficacy of an intravaginal progesterone insert and injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in cattle. Cattle were assigned to one of three treatments before a 31-d breeding period that employed artificial insemination. Control cattle were not treated, and treated cattle were administered PGF2alpha or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with PGF2alpha on d 6. The treatments were applied in one of three experiments that involved postpartum beef cows (Exp. 1; n = 851; 56+/-0.6 d postpartum), beef heifers (Exp. 2; n = 724; 442.5+/-2.8 d of age), and dairy heifers (Exp. 3; n = 260; 443.2+/-4.5 d of age). Luteal activity before treatment was determined for individual cattle based on blood progesterone concentrations. In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+PGF2alpha-treated cows compared with PGF2alpha-treated or control cows (15, 33, and 59% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+PGF2alpha, (50, 55, and 58% for control, PGF2alpha, and CIDR+PGF2alpha, respectively, P = 0.10). Improvements in rates of estrus and pregnancy after CIDR+PGF2alpha, were also observed in beef heifers. Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The PGF2alpha, and CIDR+PGF2alpha but not the control treatments were evaluated in dairy heifers (Exp. 3). The CIDR+PGF2alpha-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared with the PGF2alpha-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+PGF2alpha compared with PGF2alpha-treated heifers. In summary, the concurrent treatment of CIDR and PGF2alpha improved synchronization rates relative to PGF2alpha alone or control. Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers.     

Factors affecting pregnancy rate to estrous synchronization and fixed-time artificial insemination in beef cattle

Application of AI in extensive beef cattle production would be facilitated by protocols that effectively synchronize ovarian follicular development and ovulation to enable fixed-time AI (TAI). The objectives were to determine whether use of a controlled internal drug release (CIDR) device to administer progesterone in a GnRH-based estrous synchronization protocol would optimize blood progesterone concentrations, improve synchronization of follicular development and estrus, and increase pregnancy rates to TAI in beef cows. Beef cows (n = 1,240) in 6 locations within the US Meat Animal Research Center received 1 of 2 treatments: 1)?an injection of GnRH [100 μg intramuscularly (i.m.)] followed by PGF(2α) (PGF; 25 mg i.m.) 7 d later (CO-Synch), or 2) CO-Synch plus a CIDR during the 7 d between GnRH and PGF injections (CO-Synch + CIDR). Cows received TAI and GnRH (100 μg i.m.) at 60 h after PGF. Progesterone was measured by RIA in blood samples collected 2 wk before and at initiation of treatment (d 0) and at PGF injection (d 7). Estrous behavior was monitored by Estrotect Heat Detectors. Pregnancy was diagnosed by ultrasonography 72 to 77 d after TAI. Plasma progesterone concentrations did not differ (P > 0.10) between synchronization protocols at first GnRH injection (d 0), but progesterone was greater (P < 0.01) at PGF injection (d 7) in cows receiving CO-Synch + CIDR vs. CO-Synch as a result of fewer CIDR-treated cows having progesterone ≤1 ng/mL at PGF (10.7 vs. 29.6%, respectively). A greater (P < 0.01) proportion of CO-Synch + CIDR vs. CO-Synch cows were detected in estrus within 60 h after PGF (66.7 vs. 57.8 ± 2.6%, respectively) and a greater (P < 0.01) proportion were pregnant to TAI (54.6 vs. 44.3 ± 2.6%, respectively). For both synchronization protocols, cows expressing estrus within 60 h before TAI had a greater pregnancy rate than cows without estrus. For cows with plasma progesterone ≤1 ng/mL at PGF injection, CO-Synch + CIDR increased pregnancy rate (65.2 ± 5.9 vs. 30.8 ± 3.4% with vs. without CIDR), whereas pregnancy rates did not differ (P > 0.10) between protocols (52.1 ± 2.1 vs. 50.0 ± 2.4%, respectively) when progesterone was >1 ng/mL (treatment × progesterone; P < 0.01). Inclusion of a CIDR in the synchronization protocol increased plasma progesterone concentration, proportion of cows detected in estrus, and pregnancy rate; however, the increase in pregnancy rate from inclusion of the CIDR was primarily in cows with decreasing or low endogenous progesterone secretion during treatment.     

Evaluation of a regimen using a progesterone releasing intravaginal device (CIDR) and PMSG as a treatment for post partum anoestrus in dairy cattle

Anoestrous dairy cows in seasonally calving herds in the Macalister Irrigation District of Gippsland, Victoria were treated at the start of the mating period with a progesterone releasing intravaginal device (CIDR). The CIDR was inserted for 7 days and 400 IU of PMSG was injected intramuscularly at removal. There was no clinically useful difference among cows receiving the CIDR, a placebo and untreated cows in the interval from treatment to either first oestrus or conception, the conception rate to first service or percent pregnant by the end of mating. Analyses of data from 2-year-old cows, older cattle, cows calved at least 45 days or cows calved at least 55 days and cows treated 3 weeks after the start of mating did not show improved reproductive performance following treatment with the CIDR.     

Supplemental norgestomet,progesterone, or melengestrol acetate increases pregnancy rates in suckled beef cows after timed inseminations

In Exp. 1, 187 lactating beef cows were treated with injections of GnRH 7 d before and 48 h after prostaglandin F2alpha (PGF2alpha; Cosynch) or with Cosynch plus a 7-d treatment with an intravaginal progesterone (P4)-releasing insert (CIDR-B; Cosynch + CIDR). In Exp. 2, 183 lactating beef cows were treated with the Cosynch protocol or with Cosynch plus a 7-d treatment with norgestomet (Cosynch + NORG). In Exp. 1 and 2, blood samples for later P4 analyses were collected on d -17, -7 (first GnRH injection), 0 (PGF2alpha injection), and at timed artificial insemination (TAI; 48 h after PGF2alpha). In Exp. 3, 609 lactating beef cows were treated with the Cosynch + CIDR protocol or were fed 0.5 mg of melengestrol acetate (MGA) per day for 14 d before initiating the Cosynch protocol 12 d after the 14th d of MGA feeding (MGA + Cosynch). Blood samples were collected as in Exp. 1 and 2, plus additional samples on d -33 and -19 before PGF2alpha. In Exp. 4, 360 lactating beef cows were treated with a Cosynch + CIDR protocol, with TAI occurring at either 48 or 60 h after PGF2alpha, while receiving either GnRH or saline to form four treatments. Blood samples were collected as in Exp. 1 and 2. In Exp. 1, addition of P4 reduced the ability of the first GnRH injection to induce ovulation in anestrous cows with low P4 before PGF2alpha but improved (P = 0.06) pregnancy rates (61 vs 66%). In Exp. 2, the addition of NORG mimicked P4 by likewise increasing (P < 0.01) pregnancy rates (31 vs 51%) beyond those after Cosynch. In Exp. 3, the Cosynch + CIDR protocol increased (P < 0.001) pregnancy rates from 46 to 55% compared to the MGA + Cosynch protocol. In Exp. 4, administration of GnRH at TAI improved (P < 0.05) pregnancy outcomes (50 vs 42%), whereas timing of TAI had limited effects. We conclude that a progestin treatment concurrent with the Cosynch protocol improved pregnancy outcomes in all experiments, but pretreatment of cows with MGA was not as effective as the CIDR insert or NORG implants in this Cosynch-TAI model. Most of the improvement in pregnancy rates was associated with the increase in pregnancy rates of anestrous cows, regardless of whether ovulation was successfully induced in response to GnRH 7 d before PGF2alpha. Injection of GnRH at TAI following the Cosynch + CIDR protocol increased pregnancy rates in cycling cows with high P4 before the PGF2alpha injection and in anestrous cows with low P4 before PGF2alpha injection.     

Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone

We determined whether a fixed-time AI (TAI) protocol could yield pregnancy rates similar to a protocol requiring detection of estrus, or estrous detection plus TAI, and whether adding a controlled internal device release (CIDR) to GnRH-based protocols would enhance fertility. Estrus was synchronized in 2,598 suckled beef cows at 14 locations, and AI was preceded by 1 of 5 treatments: 1) a CIDR for 7 d with 25 mg of PG F(2alpha) (PGF) at CIDR removal, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received 100 mug of GnRH and TAI at 84 h (control; n = 506); 2) GnRH administration, followed in 7 d with PGF, followed in 60 h by a second injection of GnRH and TAI (CO-Synch; n = 548); 3) CO-Synch plus a CIDR during the 7 d between the first injection of GnRH and PGF (CO-Synch + CIDR; n = 539); 4) GnRH administration, followed in 7 d with PGF, followed by detection of estrus and AI during the 84 h after PGF; cows not detected in estrus by 84 h received GnRH and TAI at 84 h (Select Synch & TAI; n = 507); and 5) Select Synch & TAI plus a CIDR during the 7 d between the first injection of GnRH and PGF (Select Synch + CIDR & TAI; n = 498). Blood samples were collected (d -17 and -7, relative to PGF) to determine estrous cycle status. For the control, Select Synch & TAI, and Select Synch + CIDR & TAI treatments, a minimum of twice daily observations for estrus began on d 0 and continued for at least 72 h. Inseminations were performed using the AM/PM rule. Pregnancy was diagnosed by transrectal ultrasonography. Percentage of cows cycling at the initiation of treatments was 66%. Pregnancy rates (proportion of cows pregnant to AI of all cows synchronized during the synchronization period) among locations across treatments ranged from 37% to 67%. Pregnancy rates were greater (P < 0.05) for the Select Synch + CIDR & TAI (58%), CO-Synch + CIDR (54%), Select Synch & TAI (53%), or control (53%) treatments than the CO-Synch (44%) treatment. Among the 3 protocols in which estrus was detected, conception rates (proportion of cows that became pregnant to AI of those exhibiting estrus during the synchronization period) were greater (P < 0.05) for Select Synch & TAI (70%; 217 of 309) and Select Synch + CIDR & TAI (67%; 230 of 345) cows than for control cows (61%; 197 of 325). We conclude that the CO-Synch + CIDR protocol yielded similar pregnancy rates to estrous detection protocols and is a reliable TAI protocol that eliminates detection of estrus when inseminating beef cows.     

Administration of human chorionic gonadotropin to suckled beef cows before ovulation synchronization and fixed-time insemination: replacement of gonadotropin-releasing hormone with human chorionic gonadotropin

Two experiments were conducted to evaluate whether hCG administered 7 d before initiating the CO-Synch + controlled internal drug release (CIDR) ovulation synchronization protocol (Exp. 1 and 2), or replacing GnRH with hCG at the time of AI (Exp. 1), would improve fertility to a fixed-time AI (TAI) in suckled beef cows. In addition, the effects of hCG on follicle dynamics, corpus luteum development, and concentrations of progesterone (P4) were evaluated. In Exp. 1, cows were stratified by days postpartum, age, and parity and assigned randomly to a 2 × 2 factorial arrangement of 4 treatments: 1) cows received 100 μg of GnRH at CIDR insertion (d -7) and 25 mg of PGF(2α) at CIDR removal (d 0), followed in 64 to 68 h by a TAI plus a second injection of GnRH at TAI (CG; n = 29); 2) same as CG but the second injection of GnRH at the time of insemination was replaced by hCG (CH; n = 28); 3) same as CG, but cows received hCG 7 d (d -14) before CIDR insertion (HG; n = 28); and 4) same as HG, but cows received hCG 7 d (d -14) before CIDR insertion (HH; n = 29). Pregnancy rates were 52, 41, 59, and 38% for GG, GH, HG, and HH, respectively. Cows receiving hCG (39%) in place of GnRH at TAI tended (P = 0.06) to have poorer pregnancy rates than those receiving GnRH (56%). Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows with concentrations of P4 >1 ng/mL at d -7, increased (P < 0.02) concentration of P4 on d -7, and decreased (P < 0.001) the size of the dominant follicle on d 0 and 3, compared with cows not treated with hCG on d -14. In Exp. 2, cows were stratified based on days postpartum, BCS, breed type, and calf sex and then assigned to the CG (n = 102) or HG (n = 103) treatments. Overall pregnancy rates were 51%, but no differences in pregnancy rates were detected between treatments. Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows cycling on d -7 and increased (P < 0.05) concentrations of P4 on d -7 compared with pre-CO-Synch controls. Therefore, pretreatment induction of ovulation after hCG injection 7 d before initiation of CO-Synch + CIDR protocol failed to enhance pregnancy rates, but replacing GnRH with hCG at the time of AI may reduce pregnancy rates.     

Effect of addition of a progesterone intravaginal insert to a timed insemination protocol using estradiol cypionate on ovulation rate, pregnancy rate, and late embryonic loss in lactating dairy cows

The objectives of this study were to determine the effects of incorporating a progesterone intravaginal insert (CIDR) between the day of GnRH and PGF2alpha treatments of a timed AI protocol using estradiol cypionate (ECP) to synchronize ovulation on display of estrus, ovulation rate, pregnancy rate, and late embryonic loss in lactating cows. Holstein cows, 227 from Site 1 and 458 from Site 2, were presynchronized with two injections of PGF2alpha on study d 0 and 14, and subjected to a timed AI protocol (100 mixrog of GnRH on study d 28, 25 mg of PGF2alpha on study d 35, 1 mg of ECP on study d 36, and timed AI on study d 38) with or without a CIDR insert. Blood was collected on study d 14 and 28 for progesterone measurements to determine cyclicity. Ovaries were scanned on d 35, 37, and 42, and pregnancy diagnosed on d 65 and 79, which corresponded to 27 and 41 d after AI. Cows receiving a CIDR had similar rates of detected estrus (77.2 vs. 73.8%), ovulation (85.6 vs. 86.6%), and pregnancy at 27 (35.8 vs. 38.8%) and 41 d (29.3 vs. 32.3%) after AI, and late embryonic loss between 27 and 41 d after AI (18.3 vs. 16.8%) compared with control cows. The CIDR eliminated cows in estrus before the last PGF2alpha injection and decreased (P < 0.001) the proportion of cows bearing a corpus luteum (CL) at the last PGF2alpha injection because of less ovulation in response to the GnRH and greater spontaneous CL regression. Cyclic cows had greater (P = 0.03) pregnancy rates than anovulatory cows at 41 d after AI (33.8 vs. 20.4%) because of decreased (P = 0.06) late embryonic loss (16.0 vs. 30.3%). The ovulatory follicle was larger (P < 0.001) in cows in estrus, and a greater proportion of cows with follicles > or = 15 mm displayed estrus (P < 0.001) and ovulated (P = 0.05) compared with cows with follicles <15 mm. Pregnancy rates were greater (P < 0.001) for cows displaying estrus, which were related to the greater (P < 0.001) ovulation rate and decreased (P = 0.08) late embryonic loss for cows in estrus at AI. Cows that were cyclic and responded to the presynchronization protocol (high progesterone at GnRH and CL at PGF2alpha) had the highest pregnancy rates. Incorporation of a CIDR insert into a presynchronized timed AI protocol using ECP to induce estrus and ovulation did not improve pregnancy rates in lactating dairy cows. Improvements in pregnancy rates in cows treated with ECP to induce ovulation in a timed AI protocol are expected when more cows display estrus, thereby increasing ovulation rate.     

Effect of post-insemination progesterone supplementation on pregnancy rate in dairy cows

Progesterone plays an important role in maintenance of pregnancy. It is hypothesized that insufficient progesterone early in pregnancy may result in embryonic loss, and that supplemental progesterone would decrease pregnancy loss in dairy cows. In Experiment 1, 84 cows and 16 heifers from a single dairy operation were selected randomly. Within each age category, controlled internal drug release (CIDR) devices were inserted into the vagina of every other female on Day 4 post-insemination and removed on Day 18 post-insemination. Transrectal ultrasonography was performed to determine pregnancy at 4 time periods [days 30 to 37 (week 5), days 44 to 51 (week 7), days 58 to 65 (week 9), and days 86 to 93 (week 13)]. Progesterone supplementation had no effect on pregnancy rate. In Experiment 2, there were no differences in progesterone concentrations between cows that did and did not receive a CIDR. Further, cows receiving CIDR devices did not have an increase in circulating progesterone concentrations 30 min or 1 h after CIDR insertion. It appears that progesterone supplementation does not increase circulating levels of progesterone in the early pregnant lactating dairy cow. Alterative methods to influence progesterone concentrations and/or early embryonic loss need to be investigated.     

Relations between plasma IGF-I concentrations during treatment with CIDR-based or Ovsynch protocol for timed AI and conception in early postpartum Japanese black beef cows

We examined the relations between plasma insulin-like growth factor (IGF) -I concentrations during treatment with CIDR-based or Ovsynch protocol for timed AI and conception and plasma steroid concentrations in early postpartum Japanese Black beef cows. Cows in the control group (Ovsynch; n = 21) underwent Ovsynch protocol (GnRH analogue on Day 0, PGF(2alpha) analogue on Day 7, and GnRH analogue on Day 9), with AI on Day 10, approximately 20 h after the second GnRH treatment. Cows in the Ovsynch+CIDR group (n = 22) received Ovsynch protocol plus a CIDR for 7 days (starting on Day 0). Cows in the further treatment group (EB+CIDR+GnRH; n = 22) received 2 mg of estradiol benzoate (EB) on Day 0 in lieu of the first GnRH treatment, followed by the same treatment as in the Ovsynch+CIDR protocol. Plasma IGF-I concentrations were determined on Days -7, 0, 7, 9 and 17. Conception rates were improved in the CIDR-combined groups (both CIDR-treated groups were combined) relative to Ovsynch group (P < 0.05) for cows with low IGF-I concentrations (<1,000 ng/ml) on Days -7, 0, and 7, but improved conception rate produced by the CIDR-based protocols did not occur in cows with a high IGF-I concentration (> or =1,000 ng/ml). Plasma estradiol-17beta concentrations increased from Day 0 to 7 (P < 0.05) and were unchanged from Day 7 to 9 in the Ovsynch group with low IGF-I concentrations on Day 0, while they were unchanged from Day 0 to 7 and increased from Day 7 to 9 (P < 0.05) in the Ovsynch group with high IGF-I concentrations on Day 0 and in the CIDR-combined group. Plasma progesterone concentrations in the Ovsynch group with low IGF-I concentrations on Day 0 were higher on Day 14 than in the Ovsynch group with high IGF-I concentrations on Day 0 and in the CIDR-combined group (P < 0.05). In conclusion, CIDR-based protocols may improve conception relative to Ovsynch in early postpartum beef cows with lower plasma IGF-I concentrations at the start of the protocols. This improvement is probably due to prevention of premature increases of estradiol-17beta and progesterone concentrations, which occurred in cows with low IGF-I concentrations treated with Ovsynch, by the CIDR treatment.     

Ovarian, hormonal, and reproductive events associated with synchronization of ovulation and timed appointment breeding of Bos indicus-influenced cattle using intravaginal progesterone, gonadotropin-releasing hormone, and prostaglandin F2alpha

The objectives of this study were to 1) compare cumulative pregnancy rates in a traditional management (TM) scheme with those using a synchronization of ovulation protocol (CO-Synch + CIDR) for timed AI (TAI) in Bos indicus-influenced cattle; 2) evaluate ovarian and hormonal events associated with CO-Synch + CIDR and CO-Synch without CIDR; and 3) determine estrual and ovulatory distributions in cattle synchronized with Select-Synch + CIDR. The CO-Synch + CIDR regimen included insertion of a controlled internal drug-releasing device (CIDR) and an injection of GnRH (GnRH-1) on d 0, removal of the CIDR and injection of PGF2alpha (PGF) on d 7, and injection of GnRH (GnRH-2) and TAI 48 h later. For Exp. 1, predominantly Brahman x Hereford (F1) and Brangus females (n = 335) were stratified by BCS, parity, and day postpartum (parous females) before random assignment to CO-Synch + CIDR or TM. To maximize the number of observations related to TAI conception rate (n = 266), an additional 96 females in which TM controls were not available for comparison also received CO-Synch + CIDR. Conception rates to TAI averaged 39 +/- 3% and were not affected by location, year, parity, AI sire, or AI technician. Cumulative pregnancy rates were greater (P < 0.05) at 30 and 60 d of the breeding season in CO-Synch + CIDR (74.1 and 95.9%) compared with TM (61.8 and 89.7%). In Exp. 2, postpartum Brahman x Hereford (F1) cows (n = 100) were stratified as in Exp. 1 and divided into 4 replicates of 25. Within each replicate, approximately one-half (12 to 13) received CO-Synch + CIDR, and the other half received CO-Synch only (no CIDR). No differences were observed between treatments, and the data were pooled. Percentages of cows ovulating to GnRH-1, developing a synchronized follicular wave, exhibiting luteal regression to PGF, and ovulating to GnRH-2 were 40 +/- 5, 60 +/- 5, 93 +/- 2, and 72 +/- 4%, respectively. In Exp. 3, primiparous Brahman x Hereford, (F1) heifers (n = 32) and pluriparous cows (n = 18) received the Select Synch + CIDR synchronization regimen (no GnRH-2 or TAI). Mean intervals from CIDR removal to estrus and ovulation, and from estrus to ovulation were 70 +/- 2.9, 99 +/- 2.8, and 29 +/- 2.2 h, respectively. These results indicate that the relatively low TAI conception rate observed with CO-Synch + CIDR in these studies was attributable primarily to failure of 40% of the cattle to develop a synchronized follicular wave after GnRH-1 and also to inappropriate timing of TAI/GnRH-2.     

Inclusion of an intravaginal progesterone insert plus GnRH and prostaglandin F2alpha for ovulation control in postpartum suckled beef cows

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.     

Comparison of plasma concentrations of estradiol-17β and progesterone, and conception in dairy cows with cystic ovarian diseases between Ovsynch and Ovsynch plus CIDR timed AI protocols

The objectives of this study were 1) to determine the effects of adding a CIDR to the Ovsynch protocol on plasma concentrations of estradiol-17β and progesterone and conception in dairy cows with cystic ovarian diseases and 2) to examine associations among the estradiol-17β and progesterone concentrations and conception. Cows were diagnosed as having cystic ovarian diseases if they were found to have a cystic follicle (diameter ≥25 mm) without a corpus luteum by two palpations per rectum with an interval for 7 to 14 days. They were treated with either the Ovsynch (GnRH on Day 0, PGF(2α) on Day 7 and GnRH on Day 9, with AI on Day 10; n=15) or Ovsynch+CIDR protocol (Ovsynch protocol plus a CIDR from Day 0 to Day 7; n=23). Plasma estradiol-17β concentrations were determined on Days 0, 7 and 9, and plasma progesterone concentrations were determined on Days 0, 7, 9 and 17. The plasma estradiol-17β and progesterone concentrations at all of the days examined and conception rates did not differ significantly between the two timed AI protocols. The progesterone concentrations on Day 17 and conception rates were lower (P<0.05) for cows with low concentrations of estradiol-17β (<2 pg/ml) on Day 9 than for cows with high concentrations of estradiol-17β (≥2 pg/ml). The present study suggests that, in dairy cows with cystic ovarian diseases, addition of a CIDR to the Ovsynch protocol had no remarkable effects on plasma estradiol-17β and progesterone concentrations during and after the treatments or on conception after timed AI. This study indicates that the low plasma estradiol-17β concentration at the second administration of GnRH in the protocols can be a predictor for impaired luteal formation and lower likelihood of pregnancy in dairy cows with cystic ovarian diseases.