Replacing the first gonadotropin-releasing hormone treatment in an Ovsynch protocol with human chorionic gonadotropin decreased pregnancies per artificial insemination in lactating dairy cows.

Our objective was to compare the effect of treatment with GnRH at the first treatment (G1) of the Breeding-Ovsynch portion of a Double-Ovsynch (DO) protocol with human chorionic gonadotropin (hCG) on pregnancies per artificial insemination (P/AI) in lactating dairy cows. In experiment 1, lactating dairy cows (n = 1,932) submitted to a DO protocol for first timed artificial insemination (TAI) on 2 commercial dairy farms were blocked by parity (primiparous vs. multiparous) and were randomly assigned to receive 100 µg of GnRH versus 2,500 IU of hCG at G1. Overall, P/AI 39 d after TAI for cows inseminated with sexed dairy semen was greater for cows treated with GnRH than for cows treated with hCG within each parity (primiparous: 42.6% vs. 38.2%; multiparous: 39.4% vs. 30.3%). Similarly, P/AI 39 d after TAI for multiparous cows inseminated with conventional beef semen tended to be greater for cows treated with GnRH than for cows treated with hCG (41.1% vs. 34.3%). In experiment 2, lactating Holstein cows (n = 43) were blocked by parity and were randomly assigned to the treatment protocols described for experiment 1. Ovaries were evaluated with transrectal ultrasonography immediately before treatment and 24, 28, 32, 36, and 40 h after treatment to assess time from treatment to ovulation, and blood samples were collected immediately before G1, at the first PGF2α treatment, 8 and 16 h later, at the second PGF2α treatment, 8 and 16 h later, at the second GnRH (G2) treatment, and at TAI to compare luteolysis based on serum progesterone (P4) concentrations. Although mean (± standard error of the mean) time from treatment to ovulation was approximately 2 h greater for cows treated with hCG than for cows treated with GnRH (33.7 ± 0.6 vs. 31.5 ± 0.6 h), P4 concentrations during luteolysis and the proportion of cows with complete luteolysis (P4 <0.4 ng/mL at G2) did not differ between treatments. We conclude that replacing 100 µg of GnRH with 2,500 IU of hCG at G1 of a DO protocol decreased fertility to TAI in lactating dairy cows but did not affect the rate or completeness of luteolysis despite the increased interval from treatment to ovulation.

Cabrera EM ，Lauber MR ，Valdes-Arciniega T ，El Azzi MS ，Martins JPN ，Bilby TR ，Fricke PM ... -  《-》

Effect of using 200 μg of gonadorelin at the first gonadotropin-releasing hormone of the breeding-Ovsynch on ovulatory response and pregnancies per artificial insemination in first-service lactating Holstein cows.

This study aimed to determine whether 200 μg of GnRH (gonadorelin hydrochloride) would increase ovulatory response and pregnancies per artificial insemination (P/AI) compared with 100 μg at the first GnRH of the breeding-Ovsynch of a Double-Ovsynch program (DO) in lactating Holstein cows. Weekly cohorts of primiparous (n = 719) and multiparous (n = 1,191) cows submitted to DO (GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH [G1], 7 d later PGF2α [PG1], 1 d later PGF2α, ∼32 h later GnRH [G2], and ∼16 h later timed artificial insemination [TAI]) for first service, randomly received either 100 μg or 200 μg of GnRH (gonadorelin hydrochloride) at G1 (primiparous, 64-75 DIM; multiparous, 59-70 DIM). Ovulation was determined by ultrasound 2 d after G1 (n = 1,294) and 2 d after G2 (n = 1,020). Blood samples were collected at G1 and at PG1 d to evaluate serum progesterone (P4) concentrations. Conventional (n = 314, Angus; n = 1,084, Holstein) and Holstein sexed semen (n = 276) were used. Pregnancy was diagnosed on d 32, 46, 88, and 200 post-TAI. The high dose of GnRH (200 μg) increased overall ovulatory response to G1 compared with 100 μg (81.3% vs. 65.1%), being similar between parities (primiparous, 72.2%; multiparous, 73.9%). Mean serum P4 concentrations at PG1 did not differ between treatments (100 µg: 9.59 ± 0.15 ng/mL vs. 200 µg: 9.43 ± 0.15 ng/mL). Cows with no ovulation to G1 had higher serum P4 concentrations at G1 than cows with ovulation to G1 (6.27 ± 0.19 ng/mL vs. 4.66 ± 0.07 ng/mL). At PG1, the proportion of cows with functional corpus luteum (98.7% vs. 89.7%) and serum P4 concentrations (9.68 ± 0.12 ng/mL vs. 9.14 ± 0.22 ng/mL) were greater in cows that ovulated to G1 compared with cows that did not ovulate. Also, cows that ovulated to G1 had a greater increase in serum P4 concentrations from G1 to PG1 than cows with no ovulation (5.26 ± 0.12 ng/mL vs. 3.32 ± 0.25 ng/mL). The high dose of GnRH improved overall P/AI at 32 d post-TAI in cows inseminated with conventional semen (54.6% vs. 48.2%) and tended to improve P/AI on 46 (48.8% vs. 44.9%), 88 (47.6% vs. 43.4%), and 200 (45.3% vs. 41.2%) d post-TAI. Primiparous cows inseminated with conventional semen had better P/AI than multiparous cows at d 32 (58.2% vs. 49.4%), 46 (55.1% vs. 44.4%), 88 (53.2% vs. 43.2%) and 200 (51.6% vs. 40.7%) post-TAI. Primiparous cows treated with 200 µg GnRH had lower P/AI on d 32, 46, 88, and 200 post-TAI when inseminated with sexed semen than with conventional semen. In summary, the higher dose of GnRH at G1 improved ovulatory response and P/AI at d 32 post-TAI and tended to improve P/AI at d 46, 88, and 200 post-TAI in cows inseminated with conventional semen. Moreover, the effect of treatment on P/AI in primiparous cows depended on semen type (conventional vs. sexed semen).

Valdés-Arciniega TJ ，Leão IMR ，Anta-Galván E ，Cunha TO ，El Azzi MS ，Cook NB ，Martins JPN ... -  《-》

Effect of dose and timing of prostaglandin F(2α) treatments during a 7-d Ovsynch protocol on progesterone concentration at the end of the protocol and pregnancy outcomes in lactating Holstein cows.

The objective of this study was to evaluate the effect of two prostaglandin F2α (PGF) treatments 24 h apart (500 μg of cloprostenol) and treatment with a double PGF dose on d 7 (1000 μg of cloprostenol) during a 7-d Ovsynch protocol on progesterone (P4) concentration and pregnancy per artificial insemination (P/AI) in lactating Holstein cows. We hypothesized that treatment leads to a decreased P4 concentration at the second GnRH treatment (G2) and an increase in P/AI compared to the traditional 7-d Ovsynch protocol. A secondary hypothesis was that the treatment effect is influenced by the presence of a corpus luteum (CL) at the first GnRH treatment (G1). Two experiments were conducted on 8 commercial dairy farms in Germany. Once a week, cows from both experiments were assigned in a consecutive manner to receive: (1) Ovsynch (control: GnRH; 7 d, PGF; 9 d, GnRH), (2) Ovsynch with a double PGF dose (GDPG: GnRH; 7 d, 2xPGF; 9 d, GnRH), or (3) Ovsynch with a second PGF treatment 24 h later (GPPG: GnRH; 7 d, PGF; 8 d, PGF; 32 h, GnRH). All cows received timed AI (TAI) approximately 16 h after G2. Pregnancy diagnosis was performed by transrectal palpation (38 ± 3 d after TAI, experiment 1) or transrectal ultrasonography (35 ± 7 d after TAI, experiment 2). Whereas farms from experiment 1 used a Presynch-Ovsynch protocol (PGF, 14 d later PGF, 12 d later GnRH, 7 d later PGF, 2 d later GnRH, and 16-18 h later TAI) to facilitate first postpartum TAI, no presynchronization protocol was used on farms from experiment 2. In experiment 1, we enrolled 1581 lactating dairy cows (60 experimental units) from 2 dairy farms. At G2, blood samples were collected from a subsample of cows (n = 491; 16 experimental units) to determine P4 concentration at G2. In experiment 2, we enrolled 1979 lactating dairy cows (252 experimental units) from 6 dairy farms. Transrectal ultrasonography was performed to determine the presence or absence of a CL at G1. In experiment 1, treatment affected P/AI (P = 0.01) and P/AI was greater for GDPG (38.2%) and GPPG (38.9%) than for control cows (29.8%). Both, GDPG and GPPG cows had decreased P4 concentration at G2 compared with control cows (P < 0.01). Whereas both treatments increased the percentage of cows with very low P4 concentration (0.00-0.09 ng/mL) at G2, only the GPPG treatment decreased the percentage of cows with high P4 concentration (≥0.6 ng/mL) at G2 compared to the control group. In experiment 2, P/AI was greater for GPPG (37.4%) than for control cows (31.0%; P = 0.03) and tended to be greater than for GDPG cows (31.8%; P = 0.05). Cows from the GDPG group had similar (P = 0.77) P/AI compared to the control group. Pregnancy per AI did not differ between cows with a CL at G1 and cows without a CL at G1 (34.1% vs. 32.6%; P = 0.50). There was no interaction between treatment and presence of a CL at G1 on P/AI (P = 0.61). Combining data from the 2 experiments but excluding cows from experiment 1 receiving presynchronization before first TAI (n = 2573; 312 experimental units), P/AI was greater for GPPG (40.3%; P < 0.01) than for control (31.8%) and GDPG cows (33.4%). Between GDPG and control cows, P/AI did not differ (P = 0.46). We conclude that overall the addition of a second PGF treatment on d 8 during a 7-d Ovsynch protocol increased P/AI compared to the traditional 7-d Ovsynch including a single PGF dose on d 7 and to a double PGF dose on d 7. Doubling the PGF dose on d 7 in a 7-d Ovsynch protocol did not affect P/AI. Use of a presynchronization protocol, however, seems to influence the effect of a dose frequency modification of PGF treatment in an Ovsynch protocol. Presynchronized cows receiving first postpartum TAI had similarly increased P/AI treated with a double PGF dose compared with treatment with a second PGF dose. Future studies need to elucidate whether the treatment effect is modified by presynchronization of the first postpartum TAI.

Tippenhauer CM ，Steinmetz I ，Heuwieser W ，Fricke PM ，Lauber MR ，Cabrera EM ，Borchardt S ... -  《-》

Effect of dose and frequency of prostaglandin F(2α) treatments during a 7-day Ovsynch protocol with an intravaginal progesterone releasing device on luteal regression and pregnancy outcomes in lactating Holstein cows.

Our objective was to evaluate the effect of 3 different Ovsynch protocols on progesterone (P4) and pregnancies per artificial insemination (P/AI), where all cows received a P4 releasing intravaginal device (PRID) from d 0 until d 8. We hypothesized that (1) both modified PGF2α treatments lead to decreased P4 at the second GnRH treatment (G2), resulting in greater P/AI, (2) the treatment effect is influenced by the presence of a corpus luteum (CL) at the beginning of the protocol, and (3) potential vaginal discharge caused by the PRID does not have a negative influence on fertility. Lactating Holstein cows (n = 1,056) were randomly assigned to 1 of 3 treatment groups on a weekly basis (n = 356; control: d 0, 100 µg of GnRH + PRID; d 7, 25 mg of dinoprost; d 8, PRID removal; d 9, 100 µg of GnRH). Cows in the second group (n = 353) received an Ovsynch protocol with a double dose of PGF2α (DoubleDose: d 0, 100 µg of GnRH + PRID; d 7, 50 mg of dinoprost; d 8, PRID removal; d 9, 100 µg of GnRH). Cows in the third group (n = 347) received an Ovsynch protocol with a second PGF2α treatment 24 h after the first one (2PGF: d 0, 100 µg of GnRH + PRID; d 7, 25 of mg dinoprost; d 8, 25 mg of dinoprost and PRID removal; d 9, 100 µg of GnRH). All cows had their ovaries scanned to determine the presence of a CL at the beginning of the Ovsynch protocol. Vaginal discharge score (VS) was evaluated at PRID removal. All cows received timed artificial insemination approximately 16 h after G2. Pregnancy diagnosis was performed via transrectal ultrasonography (d 38 ± 3 after timed artificial insemination) and rechecked on d 80 ± 7 after timed artificial insemination. Blood samples were collected on d 0, 7, and 9 of the protocol to determine P4 concentrations. Treatment affected P4 at G2. Progesterone was lower for 2PGF and DoubleDose cows compared with cows in the control group (control 0.35 ± 0.02 ng/mL; DoubleDose 0.29 ± 0.02 ng/mL; 2PGF 0.30 ± 0.02 ng/mL). Overall, P/AI did not differ among treatments. We found, however, an interaction between treatment and CL at the first GnRH treatment. Cows lacking a CL at the first GnRH treatment in the 2PGF group had greater P/AI (47.9%) compared with the same type of cows in the DoubleDose group (32.7%). We observed an effect of VS on P4 concentration at d 7. We found an increase in P4 with greater VS. Vaginal discharge score at PRID removal tended to have a positive effect on P/AI at d 38 (VS0: 36.5%; VS1: 41.3%; VS2: 49.7%). In conclusion, the addition of a second PGF treatment on d 7 and 8 of a 7-d Ovsynch protocol increased luteal regression and decreased mean P4 at G2. Cows treated with PGF2α 2 times 24 h apart showed greater P/AI, compared with cows treated with an increased dose of PGF2α.

Hölper M ，Bretzinger L ，Randi F ，Heuwieser W ，Borchardt S ... -  《-》

Effect of extending the interval from Presynch to initiation of Ovsynch in a Presynch-Ovsynch protocol on fertility of timed artificial insemination services in lactating dairy cows.

The specific objective of this study was to determine if increasing the interval between the Presynch and Ovsynch portion of the Presynch-Ovsynch protocol (Presynch: PGF2α-14 d-PGF2α and Ovsynch: GnRH-7 d-PGF2α-56 h-GnRH-16-20 h-timed artificial insemination) from 12 to 14 d would reduce the fertility of lactating dairy cows not detected in estrus after Presynch that receive timed artificial insemination (TAI). Cows from 4 commercial dairy farms (n=3,165) were blocked by parity (primiparous vs. multiparous) and randomly assigned to a 12 (PSOv14-12; n=1,566) or 14 d (PSOv14-14; n=1,599) interval between the second PGF2α (PGF) injection of Presynch (P2) and the beginning of Ovsynch. Cows detected in estrus any time between P2 and the day of the TAI were inseminated (AIED group). From a subgroup of cows (177 and 150 in PSOv14-12 and PSOv14-14, respectively), ovarian parameters and ovulation were evaluated through determination of concentrations of progesterone (P4) in blood and transrectal ultrasonography at the time of the first GnRH (GnRH1) and the PGF injection of Ovsynch. Overall, 52.8% (n=1,671) of the cows were AIED, whereas 47.2% (n=1,494) received TAI. For cows that received TAI, pregnancies per artificial insemination 39 d after artificial insemination were similar for PSOv14-12 (36.3%) and PSOv14-14 (36.0%) but were greater for primiparous (41.5%) than multiparous cows (33.6%). Pregnancy loss from 39 to 105 d after artificial insemination was similar for PSOv14-12 (4.8%) and PSOv14-14 (8.6%), for primiparous (6.4%) and multiparous cows (7.0%), but a tendency for a treatment by parity interaction was observed. Both treatments had a similar proportion of cows with a follicle ≥ 10 mm and similar follicle size at GnRH1; however, the ovulatory response to GnRH was greater for PSOv14-12 (62.2%) than PSOv14-14 (46.4%). A greater proportion of cows with a functional corpus luteum (75.3 vs. 65.6%) and greater concentrations of P4 (3.9 vs. 3.3 ng/mL) at GnRH1 in PSOv14-14 than PSOv14-12 may have compensated for the reduction in fertility expected due to reduced ovulatory response to GnRH1. We concluded that extending the interval from Presynch to Ovsynch from 12 to 14 reduced ovulatory response to GnRH1 but did not reduce the fertility of cows that received TAI when cows were inseminated in estrus after presynchronization. Thus, farms that combine AIED and TAI during the Presynch-Ovsynch protocol may use a 14-d interval between Presynch and Ovsynch to simplify their management without reducing fertility of cows receiving TAI.

Giordano JO ，Thomas MJ ，Catucuamba G ，Curler MD ，Wijma R ，Stangaferro ML ，Masello M ... -  《-》