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).

Profitability of dairy cows submitted to the first service with the Presynch-Ovsynch or Double-Ovsynch protocol and different duration of the voluntary waiting period.

The objective of this study was to compare cash flow and parameters of economic performance for dairy cows submitted to the first service using a combination of insemination at detected estrus and timed AI (TAI) in cows synchronized with the Presynch-Ovsynch (PSOv) protocol versus all TAI after synchronization of ovulation with the Double-Ovsynch (DO) protocol with different durations of the voluntary waiting period. A secondary objective was to calculate the variation in cash flow under different input pricing scenarios through stochastic Monte Carlo simulation. Lactating Holstein cows from a commercial dairy farm were randomly assigned to 3 first-service management programs. Cows in the PSOv treatment (n = 450) received first service through a combination of insemination at detected estrus after a voluntary waiting period of 50 d in milk (DIM; i.e., after second PGF2α treatment of the protocol) and TAI at 72 ± 3 DIM. Cows in the DO60 (n = 458) and DO88 (n = 462) treatments received first service by TAI at 60 ± 3 and 88 ± 3 DIM, respectively. Individual cow cash flow was calculated for the calving interval after enrollment and for an 18-mo period after calving. Cash flow was the aggregation of daily income over feed cost, replacement cost, calf value, recombinant bovine somatotropin treatment cost, reproductive cost, and other operating expenses. All analyses were conducted separately for primiparous and multiparous cows. Continuous, binomial, and time to event outcomes were analyzed using ANOVA, logistic regression, and Cox's proportional hazard regression in SAS (SAS Institute Inc., Cary, NC). Treatments affected the dynamics of pregnancy creation, which affected time to pregnancy during lactation. As a result, we observed differences in the proportion of nonpregnant cows at the end of lactation, herd exit dynamics, lactation length, calving interval, and proportion of cows that calved again. Some of these effects varied by parity, affecting the direction and magnitude of treatment differences within parity group. For primiparous cows, maximum cash flow differences per slot for the 18-mo period were in the range of $26 (PSOv > DO60) to $29 (DO88 > DO60) but did not differ statistically. For multiparous cows, maximum cash flow differences per slot for the 18-mo period were in the range of $122 (PSOv > DO88) to $155 (DO60 > DO88) but did not differ statistically. Despite the substantial differences in cash flow (in particular for multiparous cows) caused by the effect of treatments on reproductive performance, herd exit dynamics, and calving interval, large variability in overall cash flow among individual cows and compensation between multiple outcomes resulted in lack of statistical differences in cash flow. Outcomes from the stochastic analysis indicated that similar trends for differences between treatments would be observed under varying scenarios for economic input values. In conclusion, we did not detect statistically significant cash flow differences between the PSOv, DO60, and DO88 treatments, but numerical trends and stochastic simulation indicated that the DO88 and PSOv treatments were more economically favorable than the DO60 treatment for primiparous cows. For multiparous cows, the DO60 and PSOv treatments were more economically favorable than the DO88 treatment.

Reproductive performance and herd exit dynamics of lactating dairy cows managed for first service with the Presynch-Ovsynch or Double-Ovsynch protocol and different duration of the voluntary waiting period.

The objective of this experiment was to evaluate the reproductive performance and herd exit dynamics of dairy cows managed for first service with programs varying in method of submission for insemination and voluntary waiting period (VWP) duration. Holstein cows from a commercial farm in New York were randomly allocated to receive timed artificial insemination (TAI) after the Double-Ovsynch protocol (GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI) at 60 ± 3 d in milk (DIM) (DO60 = 458), TAI after Double-Ovsynch at 88 ± 3 DIM (DO88 = 462), or a combination of AI at detected estrus (starting at 50 ± 3 d in milk) and TAI with the Presynch-Ovsynch protocol (PGF2α, 14 d later PGF2α, 12 d later GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI; PSOv = 450). Subsequent artificial insemination (AI) services were conducted at detected estrus or the Ovsynch protocol (32 ± 3 d after AI GnRH, 7 d later PGF2α, 56 h later GnRH, and 16 to 18 h later TAI) for cows not reinseminated at detected estrus. In a subgroup of cows, cyclicity (based on progesterone concentration), uterine health (vaginal discharge and uterine cytology), and BCS were evaluated at baseline (DO60 and DO88 = 33 ± 3 DIM; PSOv = 34 ± 3 DIM), beginning of the synchronization protocol (DO60 = 33 ± 3 DIM; DO88 = 61 ± 3 DIM; PSOv = 34 ± 3 DIM), and within -5 (PSOv) or -10 d (DO) of the VWP end (DO60 = 50 ± 3 DIM; DO88 = 78 ± 3 DIM; PSOv = 45 ± 3 DIM). Effects of treatments were assessed with multivariable statistical methods relevant for each outcome variable. Cows in the DO88 treatment had delayed time to pregnancy during lactation (DO60 vs. DO88 hazard ratio = 1.53, 95% confidence interval = 1.32 to 1.78; PSOv vs. DO88 hazard ratio = 1.37, 95% confidence interval = 1.19 to 1.61) and, within multiparous cows, the DO88 and PSOv treatments had greater risk of leaving the herd than cows in the DO60 treatment (DO88 vs. DO60 hazard ratio = 1.49, 95% confidence interval = 1.11 to 2.00; PSOv vs. DO60 hazard ratio = 1.39, 95% confidence interval = 1.03 to 1.85). Cows in the DO88 treatment had improved uterine health, greater BCS, and reduced incidence of anovulation than cows in DO60 and PSOv; however, overall pregnancy per AI 39 ± 3 d after AI was similar for the 3 treatment groups. In summary, reproductive management strategies that led to similar average DIM to the first service (∼60 d) through a combination of AI at estrus with TAI (PSOv) or all TAI (DO60) resulted in reduced time to pregnancy after calving when compared with an all TAI program (DO88) with a VWP of 88 d. Within the multiparous cow group, those that received all TAI with a VWP duration of 60 d were less likely to leave the herd than cows in the other treatments.

Performance of automated activity monitoring systems used in combination with timed artificial insemination compared to timed artificial insemination only in early lactation in dairy cows.

Identifying cows in estrus remains a challenge on dairy cattle farms, and tools and technologies have been developed and used to complement or replace visual detection of estrus. Automated activity monitoring (AAM) systems and timed artificial insemination (TAI) are technologies available to dairy farmers, but many factors can influence their relative performance. The objective of the present study was to compare reproductive performance of cows managed with an AAM system combined with TAI, or with a TAI program (Double Ovsynch) for insemination before 88 DIM. From April 2014 to April 2015, 998 cows from 2 herds were randomly assigned either to be inseminated at 85 ± 3 DIM exclusively using the Double Ovsynch protocol for TAI, or to be inseminated based on estrus detection by AAM without hormonal intervention between 50 and 75 DIM; if no alarm was detected by 75 DIM, cows were inseminated following the single Ovsynch protocol (AAM + Ovsynch). The herds used different AAM systems. Parity, hyperketonemia at wk 1 and 2 postpartum (PP), purulent vaginal discharge at wk 5 PP, body condition score at wk 7 PP, and anovulation to wk 9 PP were recorded. These health indicators did not significantly differ between treatments, but did between herds. The effect of treatment on pregnancy at first insemination and by 88 DIM were assessed using logistic regression models. Time to pregnancy was assessed using survival analysis. Results are reported from intention-to-treat analyses. Treatment did not affect pregnancy at first insemination or pregnancy by 88 DIM, but we found significant interactions between treatment and herd for both outcomes. In herd 2, marginal mean pregnancy at first AI was greater with Double Ovsynch (38%) than AAM + Ovsynch (31%), but no difference was observed in herd 1 (Double Ovsynch = 31%; AAM + Ovsynch = 34%). By 88 DIM, a smaller proportion of cows in herd 1 were pregnant in Double Ovsynch (31%) than AAM + Ovsynch (49%), but there was no difference in herd 2 (Double Ovsynch = 38%; AAM + Ovsynch = 38%). We observed a treatment by herd interaction for median (95% confidence interval) time to pregnancy, which were, in herd 1, 110 (106 to 129) and 98 (88 to 113) d, and, in herd 2, 126 (113 to 139) and 116 (105 to 131) d for the Double Ovsynch and AAM + Ovsynch treatments, respectively. The relative performance of AAM-based reproductive management compared with TAI only is likely influenced by herd-specific variables, in particular related to insemination rate when estrus detection is employed.

Evaluation of prostaglandin F2α versus prostaglandin F2α plus gonadotropin-releasing hormone as Presynch methods preceding an Ovsynch in lactating dairy cows: A meta-analysis.

Presynchronization of cows with 2 injections of prostaglandin administered 14 d apart (Presynch-Ovsynch) is a widely adopted procedure to increase pregnancy per artificial insemination (P/AI) at first service. Recently, a presynchronization protocol including GnRH and PGF2α (Double-Ovsynch; GnRH, 7 d, PGF2α, 3 d, GnRH) followed 7 d later by an Ovsynch protocol was introduced to overcome the limitations of PGF2α-based protocols for presynchronization of anovular cows and to precisely set up cows on d 7 of the estrous cycle when the Ovsynch is initiated. A systematic review of the literature and a meta-analytical assessment was performed with the objective to compare the reproductive performance of lactating dairy cows presynchronized with these 2 protocols for the first timed AI (TAI) considering parity-specific effects. A fixed or a random effects meta-analysis was used based on the heterogeneity among the experimental groups. Reproductive outcomes of interest were P/AI measured on d 32 (28-42) and pregnancy loss between d 32 and 60 (42-74) of gestation. A total of 25 articles with 27 experimental groups from 63 herds including 21,046 cows submitted to first TAI using either a Presynch-Ovsynch or a Double-Ovsynch protocol were reviewed. Results for P/AI were then categorized by parity if available. Information was available for P/AI for 7,400 and 10,999 primiparous and multiparous cows, respectively. Information regarding pregnancy loss was available for 7,477 cows. In the random effects model for all cows, the overall proportion of P/AI was 41.7% [95% confidence interval (CI): 39.1-44.3; n = 8,213] and 46.2% (95% CI: 41.9-50.5; n = 12,833) on d 32 after TAI for Presynch-Ovsynch and Double-Ovsynch, respectively. In the random effects model for primiparous cows, the overall proportion of P/AI was 43.4% (95% CI: 36.2-47.7; n = 2,614) and 51.4% (95% CI: 47.4-55.4; n = 4,786) on d 32 after TAI for Presynch-Ovsynch and Double-Ovsynch, respectively. In the random effects model for multiparous cows, the overall proportion of P/AI was 39.2% (95% CI: 36.2-42.3; n = 3,411) and 41.4% (95% CI: 36.4-46.4; n = 7,588) on d 32 after TAI for Presynch-Ovsynch and Double-Ovsynch, respectively. The overall proportion of pregnancy loss was 11.3% (95% CI: 7.6-15.7; n = 3,247) and 11.7% (95% CI: 9.3-14.3; n = 4,230) on d 60 after AI for Presynch-Ovsynch to and Double-Ovsynch, respectively. Substantial heterogeneity existed among the experimental groups regarding P/AI and pregnancy loss. In summary, a benefit was detected for P/AI in primiparous cows presynchronized with a Double-Ovsynch protocol for the first TAI, but this benefit was not observed in multiparous cows.

Presynchronization using a modified Ovsynch protocol or a single gonadotropin-releasing hormone injection 7 d before an Ovsynch-56 protocol for submission of lactating dairy cows to first timed artificial insemination.

Presynchronization strategies, such as Presynch-Ovsynch and Double-Ovsynch, increase fertility to timed artificial insemination (TAI) compared with Ovsynch alone; however, simpler presynchronization strategies could reduce costs and simplify reproductive management. Lactating Holstein cows (n=601) were randomly assigned to 1 of 2 presynchronization treatments before beginning an Ovsynch-56 protocol (GnRH at 70 ± 3 DIM, PGF2α 7 d later, GnRH 56 h after PGF2α, and TAI 16 h later at 80 ± 3 DIM) for first TAI. Cows (n=306) in the first treatment (Double-Ovsynch; DO) were presynchronized using a modified Ovsynch protocol (GnRH at 53 ± 3 DIM, 7 d later PGF2α, and GnRH 3 d later) ending 7 d before the first GnRH injection (G1) of an Ovsynch-56 protocol. Cows (n=295) in the second treatment (GGPG) were presynchronized using a single injection of GnRH 7 d before G1 of an Ovsynch-56 protocol at 63 ± 3 DIM. Blood samples were collected at G1 and the PGF2α injections of the Ovsynch-56 protocol to determine progesterone (P4) concentrations. Pregnancy diagnosis was performed using ultrasonography 32 d after TAI, and pregnant cows were reexamined 46 and 70 d after TAI. Overall, DO cows had more pregnancies per artificial insemination (P/AI) compared with GGPG cows 32 d after TAI (53 vs. 43%). Overall, P/AI did not differ by parity (primiparous vs. multiparous), and pregnancy loss did not differ between treatments or parities. More DO cows had P4 in a medium range (>0.5 to <4 ng/mL) at G1 of the Ovsynch-56 protocol compared with GGPG cows (82 vs. 50%), and more DO cows had high P4 (>4 ng/mL) at the PGF2α injection of the Ovsynch-56 protocol compared with GGPG cows (67 vs. 36%). Thus, presynchronization with a modified Ovsynch protocol increased P/AI after TAI at first AI by increasing synchrony to the Ovsynch-56 protocol compared with presynchronization using a single injection of GnRH.

Effect of Double-Ovsynch and Presynch-Ovsynch on postpartum ovarian cysts and inactive ovary in high-yielding dairy cows.

Introduction: Optimizing the management of dairy cattle reproduction can reduce postpartum ovarian disease in high-yielding dairy cows and thus enhance ranch economic benefit. The hypothesis of this study was that the Double-Ovsynch (DO) protocol in high-producing dairy cows would result in a lower incidence of follicular cysts but a higher incidence of luteal cysts compared to those undergoing the Presynch-Ovsynch (PS) protocol. Methods: In this experiment, 384 cows (204 primiparous and 180 multiparous) were allocated to the DO group, which followed the protocol: GnRH-7d-PGF2α-3d-GnRH-7d-Ovsynch-56 h (GnRH-7d-PGF2α-56 h-GnRH-16hTAI), starting on 39 ± 3 days in milk (DIM). Additionally, 359 cows (176 primiparous and 183 multiparous) were assigned to the PS group, which followed the protocol: PGF2α-14d-PGF2α-12d-Ovsynch-56 h, starting on 31 ± 3 DIM. In DO, B-mode ultrasound examinations were conducted 1 day after the GnRH-7d-PGF2α-3d-GnRH protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days of suspected cases. In PS, B-mode ultrasound examinations were conducted 1 day after the PGF2α-14d-PGF2α protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days. For all cows confirmed to having ovarian diseases, a second B-mode ultrasound examination was conducted at the time of the second GnRH and timed artificial insemination (TAI). If the ovary showed a normal developing follicle in combination with normal ovulation, the ovarian disease was considered to be cured. Results: The current study revealed no significant difference in the overall incidence and cure rate of postpartum ovarian diseases between DO and PS (incidence rate: 3.9% vs. 6.7%, cure rate: 50% vs. 41.7%, DO vs. PS). Also, there was no significant difference in the incidence and cure rate of luteal cysts between DO and PS (incidence rate: 2.9% vs. 2.2%, cure rate: 50.0% vs. 50.0%). The incidence of follicular cysts was significantly lower in the DO group than in the PS group (0.8% vs. 2.8%, DO vs. PS, p = 0.037), but there was no significant difference in the cure rates (66.7% vs. 50%). The occurrence of inactive ovary was lower in DO compared to PS (0.2% vs. 1.7%, p = 0.047). There was no significant difference in the pregnancy rate between the DO and PS groups (48.2% vs. 41.8%), although the DO group had a higher rate. What is different from our assumption is that PS did not effectively reduce the incidence of postpartum luteal cysts.

Comparison of three reproductive management strategies for lactating dairy cows using combination of estrus detection or ovulation synchronization and Fixed-Timed Artificial Insemination.

The objective of this study was to compare the reproductive performance of lactating dairy cows submitted to first AI after combination of estrus detection and fixed timed AI (FTAI) and FTAI only. Cows were randomly assigned to receive AI at detected estrus between 50 and 70 d in milk (DIM), if not detected in estrus, were enrolled in either Ovsynch (ED-Ov, n = 485) or PRIDsynch (ED-PR, n = 505) protocols; or received FTAI at 80 DIM after Double-Ovsynch protocol (DO, n = 501). Cows were body condition scored (BCS) at calving and at 43 DIM; and evaluated for postpartum disorders within 7 d postpartum; clinical mastitis, lameness and bovine respiratory disease were recorded until first AI. Ovarian cyclicity was monitored at 43 and 50 DIM, and at 70 and 77 DIM. Pregnancy diagnoses (PD) were performed at 32 and 63 d after AI. Overall prevalence of postpartum anovulation was 7.8%. Pregnancy per AI (P/AI) did not differ between reproductive strategies at 32 d PD (ED-Ov = 43.2%; ED-PR = 41.7%; DO= 45.3%). Primiparous cows had greater P/AI than multiparous cows (53.7% vs 36.8%). Cows on farm 1 had lower P/AI compared with their counterparts on farm 2 (42.1% vs 45.4%). Cows with BCS > 2.5 at 43 DIM had greater P/AI compared with cows with BCS ≤ 2.5 (44.5% vs 34.7%). Similar P/AI for cow's receiving AI at detected estrus and FTAI, low prevalence of disease anovulation may have contributed to the similar performance of ED-Ov, ED-PR and DO.

Benefits of using Double-Ovsynch versus presynch-ovsynch are affected by environmental heat in primiparous holstein lactating cows.

Optimized reproduction management enhances fertility of dairy cows, and thus improves their milk production efficiency. Comparing different synchronization protocols under variable ambient conditions would be conducive to protocol selection and production efficiency improvement. Here, 9538 primiparous Holstein lactating cows were enrolled to either Double-Ovsynch (DO) or Presynch-Ovsynch (PO) to determine the outcomes under different ambiences. We found that averaged THI of 21-days before the first service (THI-b) was the best indicators in a total of 12 environmental indexes to explain changes in conception rate. And the conception rate decreased linearly in DO treated cows when THI-b was over 73, whereas the threshold was 64 in cows subjected to PO. Compared with PO treated cows, DO increased conception rate by 6%, 13% and 19%, when THI-b was lower than 64, from 64 to 73, and over 73, respectively. Furthermore, employing treatment of PO would lead greater risk for cows staying open compared with DO when THI-b below 64 (hazard ratio, 1.3) and over 73 (hazard ratio, 1.4). Most importantly, calving intervals were 15 days shorter in DO treated cows compared PO when THI-b over 73, while no difference was detected when THI-b below 64. In conclusion, our results supported that, fertility of primiparous Holstein cows could be improved by employing DO, especially in hot weather (THI-b ≥ 73), and the benefits of DO protocol were abated under cool conditions (THI-b < 64). Considering the impacts of environmental heat load is necessary to determine reproductive protocols for commercial dairy farm.

Efficacy of a modified Double-Ovsynch protocol for the enhancement of reproductive performance in Hanwoo cattle.

OBJECTIVE: We aimed to evaluate the efficacy of a modified Double-Ovsynch protocol vs artificial insemination following estrus detection (AIED) for the enhancement of reproductive performance in Hanwoo cattle. METHODS: Four hundred twelve Hanwoo cows were allocated to two treatment groups. The first group of cows were administered gonadotropin releasing hormone (GnRH) on Day 36 (±0.6), prostaglandin F2α (PGF2α) on Day 46 (8 to 12 days later), and GnRH on Day 49, which was followed by Ovsynch, consisting of an injection of GnRH on Day 56, PGF2α on Day 63, and GnRH 56 h and timed AI (TAI) 16 h later (modified Double-Ovsynch group, n = 203). The second group of cows underwent AIED (AIED group, n = 209) and were designated as controls. RESULTS: The pregnancy per AI 60 days after the first AI was higher in the modified Double- Ovsynch (68.5%) than in the AIED (56.5%) group, resulting in a higher probability of pregnancy per AI (odds ratio: 1.68, p<0.05). Moreover, cows in the modified Double- Ovsynch group were more likely (hazard ratio: 1.28, p<0.05) to be pregnant by 150 days after calving than cows in the AIED group, and this difference was associated with a lower mean number of AIs per conception (1.27 vs 1.39, p<0.05) and a shorter median interval between calving and pregnancy (72 vs 78 days, p<0.1). CONCLUSION: The modified Double-Ovsynch protocol, adjusted according to the herd visit schedule, can be readily used to increase the pregnancy per AI following the first AI and to shorten the interval between calving and pregnancy in beef herds.

Treatment of cows that fail to respond to pre-synchronization treatments with a CIDR-Ovsynch regimen improves the overall pregnancy percentage after a double Ovsynch treatment regimen.

In this study, there was evaluation of pregnancy per AI (P/AI) as a result of the first postpartum AI following four ovulation-synchronization treatments. Treatment regimens were Ovsynch-56 (OVS, n = 875; GnRH1-7d-PGF2α-56h-GnRH2-16h-FTAI), CIDR-OVS (n = 1001; OVS plus CIDR inserts between GnRH1 and PGF2α), Double-Ovsynch (DOVS, n = 663; imposing Pre-OVS followed by breeding-OVS 7 days later), and Modified-DOVS (M-DOVS, n = 1397; imposing Pre-OVS followed either by breeding-OVS or CIDR-OVS based upon the ovarian structure at GnRH1). Cows with a corpus luteum were assigned to a breeding-OVS treatment regimen and those that did not have a corpus luteum were assigned to the CIDR-OVS treatment regimen. Compared with OVS, the P/AI of the cows in the M-DOVS (OR = 1.5, P = 0.001) and CIDR-OVS (OR = 1.4, P = 0.017) was greater at day 30. At day 70, only in the M-DOVS group was there a greater P/AI compared with the OVS group (OR = 1.7, P < 0.001). Pregnancy loss between days 30 and 70 was greater in cows of the CIDR-OVS (OR = 1.9, P = 0.014) compared with those of the OVS group. In cows of the M-DOVS, the dominant ovarian structures (follicle, corpus luteum or cyst) at different time-points of the pre-synchronization period and occurrence of estrus at the end of this period were not associated with P/AI at day 30 post-AI. In conclusion, imposing CIDR-OVS in cows that did not respond to pre-synchronization treatments, resulted in an enhanced pregnancy percentage with the use of the DOVS.

Reproductive performance following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program in Korean dairy herds.

We aimed to compare the reproductive performance of dairy cattle following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program (CRMP). On Day 30 (±5) after calving (calving = Day 0), 960 lactating cows were assigned randomly to one of two presynchronization treatments, before the synchronization of ovulation (Ovsynch) or CRMP without presynchronization. Cows were administered prostaglandin F2α (PGF2α) on Days 38 (±5) and 52, and gonadotropin-releasing hormone (GnRH) on Day 55 (Presynch-G-Ovsynch group, n = 333); or GnRH on Day 45 (±5), PGF2α on Day 52, and GnRH again on Day 55 (Double-Ovsynch group, n = 307). Thereafter, each cow underwent Ovsynch 7 days later: GnRH on Day 62, PGF2α on Day 69, and GnRH again 56 h later, followed by timed artificial insemination (AI) 16 h later. The remaining cows underwent AI when estrus was detected or Ovsynch (CRMP group, n = 320). In a subset of cows (each n = 40) in the two presynchronization groups, blood collections and ovarian ultrasonography were performed on Days 30 (±4), 52, 62, and 69, and uterine cytology on Days 30 (±4) and 52. The probabilities of pregnancy per AI 32 and 60 days after the first AI were higher in the Presynch-G-Ovsynch (odds ratio [OR]: 1.89 and 1.81, P < 0.01) and Double-Ovsynch (OR: 1.63 and 1.60, P < 0.05) groups than in the CRMP group. The likelihood of pregnancy by 210 days postpartum was higher (P < 0.05) in Presynch-G-Ovsynch (hazard ratio [HR]: 1.29) and Double-Ovsynch (HR: 1.31) groups than in the CRMP group, whereas the least square mean number of inseminations per conception was lower (P < 0.05) in Presynch-G-Ovsynch (1.8) and Double-Ovsynch (1.8) groups than in the CRMP group (2.1). The percentages of cows with serum progesterone concentrations ≥1.0 ng/mL or with a corpus luteum (CL) did not differ between the groups (P > 0.1) on Days 30, 62, and 69, but were lower (P < 0.05) on Day 52 in the Presynch-G-Ovsynch than in the Double-Ovsynch groups. However, the diameter of the dominant follicles, the proportion of neutrophils in uterine cytological samples, and the prevalence of an accessory CL on Day 69 did not differ (P > 0.1) between the two groups. In conclusion, both the Presynch-G-Ovsynch and Double-Ovsynch programs improved reproductive performance vs. CRMP in smallholder Korean dairy herds, and there were no differences in the ovarian endocrine and structural dynamics, or uterine health, between the two programs involving presynchronization.

Ovulation and fertility response to commercially available GnRH products in lactating cows synchronized with the Double-Ovsynch protocol.

This study was designed to evaluate whether commonly used gonadorelin products that are commercially available in the United States results in comparable ovulation and pregnancy per AI (P/AI) in synchronized lactating dairy cows. A total of 1411 Holstein cows receiving a Double-Ovsynch protocol (DOV) for conducting the first postpartum AI were randomized to receive one of the following GnRH products throughout the Double-Ovsynch: 1) Cystorelin® (CYS, gonadorelin diacetate tetrahydrate, n = 484); 2) Factrel® (FAC, gonadorelin hydrochloride, n = 482) or; 3) Fertagyl® (FER, gonadorelin diacetate tetrahydrate, n = 515). A subgroup of cows (n = 487) received ovarian ultrasound exams and collection of blood samples for progesterone (P4) analysis. Proportion of cows ovulating following the 3rd GnRH of DOV tended (P = 0.07) to differ between GnRH salts (hydrochloride = 61.5% vs. diacetate = 72.7%) but was similar for GnRH products (FER = 74.1% vs. FAC = 61.5% vs. CYS = 72.2%). Interestingly, a logistic regression analyses that considered the circulating P4 at the time of GnRH treatment indicated lower ovulation responses to FAC compared to FER and CYS; although greater circulating P4 decreased ovulation response to all GnRH products. Results for P/AI at 60 d post-insemination differed between GnRH salts (P = 0.02) as well as GnRH products (FER = 47.8% vs. FAC = 42.0% vs. CYS = 49.8%; P = 0.04). In conclusion, fertility following use of the Double-Ovsynch was less following a hydrochloride-based GnRH product likely due to lesser ovulatory responses throughout the synchronization protocol.

Presynchronization by induction of a largest follicle using a progesterone device in GnRH-based-ovulation synchronization protocol in crossbred dairy cows.

The objective was to compare the fertility of dairy cows using a presynchronization protocol by induction of a largest follicle using a progesterone intravaginal device prior to an Ovsynch protocol (P4synch) with the Double-Ovsynch in lactating dairy cows. Lactating Bos indicus x Bos taurus crossbred cows (n = 440) were randomly allocated to one of two treatments: (I) Double-Ov (n = 228), GnRH (D-17), PGF2α 7 days later (D-10) and GnRH 3 days later (D-7) followed by an Ovsynch protocol 7 days later (GnRH on D0, PGF on D7, GnRH on D9); (II) P4synch (n = 212), insertion of a sustained release progesterone intravaginal device (D-10), 10 days later (D0) an Ovsynch protocol was initiated (GnRH on D0, PGF on D7, GnRH on D9) with progesterone device withdrawal on Day 7. All cows were artificially inseminated (TAI) 16 h after the second GnRH of the Ovsynch protocol and pregnancy diagnosis was performed by transrectal ultrasonography 30 and 60 days after TAI. A subset of cows (n = 52 for Double-Ov and n = 50 for P4synch) ultrasonography was performed on days 0, 7, 9 and 24 of the experimental period. There were no differences among treatments on presynchronization rate [presence of a follicle>12 mm on D0, Double-Ov 94.2% (49/52) and P4synch 92.0% (46/50); P = 0.66], follicular diameter on the 1st GnRH (Double-Ov 17.2 ±â€¯0.7 mm e P4synch 18.6 ±â€¯0.9 mm; P = 0.28), ovulation rate to the 1st GnRH [Double-Ov 86.3% (44/51) and P4synch 81.2% (39/48); P = 0.50], synchronization rate [presence of a follicle>12 mm on D9; Double-Ov 84.6% (44/52) and P4synch 86.0% (43/50); P = 0.84], follicular diameter on the 2nd GnRH (Double-Ov 17.5 ±â€¯0.6 mm and P4synch 18.0 ±â€¯0.5 mm; P = 0.48), ovulation rate to the 2nd GnRH [Double-Ov 90.9% (40/44) and P4synch 86.0% (37/43); P = 0.48] and CL diameter on D24 (Double-Ov 27.9 ±â€¯0.7 mm and P4synch 29.4 ±â€¯0.9 mm; P = 0.19). Corpus luteum presence on D0 was different (P = 0.03) among treatments [Double-Ov 57.7% (30/52) and P4synch 36.0% (18/50)]. There was no difference (P = 0.85) among the pregnancy per AI on day 30 [Double-Ov 39.0% (89/228) and P4synch 40.1% (85/212)], on day 60 [Double-Ov 34.8% (79/227) and P4synch 38.7% (82/212); P = 0.41] and pregnancy loss [Double-Ov 10.2% (9/88) and P4synch 3.5% (3/85); P = 0.08]. The presynchronization by induction of a largest follicle using a sustained release progesterone device prior to Ovsynch yielded similar results compared with the Double Ovsynch protocol on follicular development patterns and on the fertility of lactating dairy cows.

Early postpartum administration of equine chorionic gonadotropin to dairy cows calved during the hot season: Effects on fertility after first artificial insemination.

Heat stress reduces fertility of high-producing dairy cows, and early administration of equine chorionic gonadotropin (eCG) may improve it. Here, 401 heat-stressed, high-producing dairy cows on a single commercial farm were given eCG (500 UI, n = 214) or saline (n = 187) on days 11-17 after calving, and the effects on fertility after the first artificial insemination (AI) were assessed. On post-partum day 96.34 ± 9.88, all cows were inseminated after a "double short Cosynch" synchronization protocol. Ovarian activity and uterine status were checked by ultrasound on the day of eCG administration and every 7 days thereafter for a total of 3 weeks; checks were also performed during synchronization, and 7 days after AI. On post-partum day 30, cytobrush uterine cytology was performed to check for subclinical endometritis. Pregnancy status was checked on days 30 and 60 after AI. The eCG and control groups did not differ significantly in terms of average lactations per cow (2.33 ± 1.34), days in milk at first AI (96.33 ± 9.88), average milk yield at AI (41.38 ± 7.74 L), or the particular inseminator or bull used for AI. The eCG and control groups showed increasing ovarian activity with time, with approximately 75% of cows in both groups showing a corpus luteum at the beginning of the synchronization protocol. On post-partum day 30, 17.4% of eCG cows and 22.9% of control cows showed subclinical endometritis. Cows treated with eCG showed a tendency toward lower hyperecogenic intraluminal content (16.8 vs. 21.4%, P = 0.15), but ovarian activity during the synchronization protocol was similar between eCG and control groups, with 91% of animals in both groups showing luteolysis after prostaglandin application and 88% showing ovulation after the last administration of gonadotropin-releasing hormone. Fertility was similar between the two groups at both time points after AI (30 days, 34.9 vs. 31.8%; 60 days, 30.6 vs. 28.5%; P > 0.2). These results suggest that early postpartum eCG administration does not improve fertility of heat-stressed dairy cows as long as 60 days after AI. Other strategies may be more effective at mitigating the ability of post-partum heat stress to reduce fertility of high-producing dairy cows.

Double-Ovsynch, compared with presynch with or without GnRH, improves fertility in heat-stressed lactating dairy cows.

The objective was to compare 3 timed artificial insemination (TAI) protocols in lactating dairy cows during heat stress. Multiparous Holstein cows yielding (mean ± SEM) 29.4 ± 0.3 kg of milk/d randomly were assigned to 1 of 3 TAI protocols at 34 ± 5.1 days in milk: 1) double-Ovsynch (DO; n = 486): the cows received GnRH-7d-2α-3d-GnRH and Ovsynch56 (GnRH-7d-PGF2α-56h-GnRH-16h-AI) was initiated 7 days later; 2) Presynch-GnRH-Ovsynch (PGO; n = 453): the cows received PGF2α-14d-PGF2α-2d-GnRH and Ovsynch56 was initiated 7 days later; and 3) presynch-Ovsynch (PO; n = 435): the cows received PGF2α-14d-PGF2α and Ovsynch56 was initiated 12 days later. The ovulatory response to the first GnRH of Ovsynch56 was higher in DO (65.0%) compared to PGO (53.2%) and PO (45.5%). Luteolytic response to PGF2α of Ovsynch was similar among TAI protocols (90.1%, 87.1%, and 86.2% for DO, PGO, and PO, respectively). Synchronization rate was greater in DO (86.2%) than in PGO (78.1%) and PO (72.1%) protocols. Irrespective of the TAI protocol, cows that ovulated in response to first GnRH had greater response to PGF2α (92.7 vs. 77.1%). Mean (±SEM) diameter (mm) of ovulatory follicle at TAI was larger in DO (16.1 ± 0.3) than PGO (15.6 ± 0.21) and PO (15.2 ± 0.12). Cows subjected to DO had greater P/AI at 32 days and at 60 days after TAI (26.6 and 24.4%) compared with those in PGO (21.4 and 20.0%) and PO (17.2 and 15.9%). However, TAI protocol had no significant effect on the incidence of pregnancy loss (6.1%, 6.6%, and 7.4% for DO, GO, and PO, respectively). In summary, cows in the DO protocol had a greater ovulation rate to the first GnRH and a greater synchronization rate, larger ovulatory follicles and greater P/AI. Of the 3 protocols used, DO yield the best reproductive performance in heat-stressed, lactating dairy cows.

Effect of increasing GnRH and PGF2α dose during Double-Ovsynch on ovulatory response, luteal regression, and fertility of lactating dairy cows.

Ovsynch-type synchronization of ovulation protocols have suboptimal synchronization rates due to reduced ovulation to the first GnRH treatment and inadequate luteolysis to the prostaglandin F2α (PGF2α) treatment before timed artificial insemination (TAI). Our objective was to determine whether increasing the dose of the first GnRH or the PGF2α treatment during the Breeding-Ovsynch portion of Double-Ovsynch could improve the rates of ovulation and luteolysis and therefore increase pregnancies per artificial insemination (P/AI). In experiment 1, cows were randomly assigned to a two-by-two factorial design to receive either a low (L) or high (H) doses of GnRH (Gonadorelin; 100 vs. 200 µg) and a PGF2α analogue (cloprostenol; 500 vs. 750 µg) resulting in the following treatments: LL (n = 263), HL (n = 277), LH (n = 270), and HH (n = 274). Transrectal ultrasonography and serum progesterone (P4) were used to assess ovulation to GnRH1, GnRH2, and luteal regression after PGF2α during Breeding-Ovsynch in a subgroup of cows (n = 651 at each evaluation). Pregnancy status was assessed 29, 39, and 74 days after TAI. In experiment 2, cows were randomly assigned to LL (n = 220) or HH (n = 226) treatment as described for experiment 1. For experiment 1, ovulation to GnRH1 was greater (P = 0.01) for cows receiving H versus L GnRH (66.6% [217/326] vs. 57.5% [187/325]) treatment, but only for cows with elevated P4 at GnRH1. Cows that ovulated to GnRH1 had increased (P < 0.001) fertility compared with cows that did not ovulate (52.2% vs. 38.5%); however, no effect of higher dose of GnRH on fertility was detected. The greater PGF2α dose increased luteal regression primarily in multiparous cows (P = 0.03) and tended to increase fertility (P = 0.05) only at the pregnancy diagnosis 39 days after TAI. Overall, P/AI was 47.0% at 29 days and 39.7% at 74 days after TAI; P/AI did not differ (P = 0.10) among treatments at 74 days (LL, 34.6%; HL, 40.8%; LH, 42.2%; HH, 40.9%) and was greater (P < 0.001) for primiparous cows than for multiparous cows (46.1% vs. 33.8%). For experiment 2, P/AI did not differ (P = 0.21) between H versus L treatments (44.2% [100/226] vs. 40.5% [89/220]). Thus, despite an increase in ovulatory response to GnRH1 and luteal regression to PGF2α, there were only marginal effects of increasing dose of GnRH or PGF2α on fertility to TAI after Double-Ovsynch.