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.     

Preventive effects of CIDR-based protocols on premature ovulation before timed-AI in Ovsynch in cycling beef cows

Ovsynch is a program developed to synchronize ovulation for timed breeding. In this paper, the authors investigate whether controlled internal drug release (CIDR)-based protocols prevent premature ovulation before timed-artificial insemination (AI) when Ovsynch is started a few days before luteolysis in cycling beef cows. Nine beef cows at 16 days after oestrus were treated with (1) Ovsynch, i.e. gonadotropin releasing hormone (GnRH) analogue on day 0, prostaglandin (PG) F(2alpha) analogue on day 7 and GnRH analogue on day 9 with timed-AI on day 10, (n=3); (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from day 0, n=3), or (3) oestradiol benzoate (OB)+CIDR+GnRH (OB on day 0 in lieu of the first GnRH treatment, followed by the Ovsynch+CIDR protocol, n=3). In the Ovsynch group (1) plasma progesterone concentrations fell below 0.5 ng/mL earlier (day 5) than in both CIDR-treated groups (2) and (3), where this occurred on day 8. Plasma oestradiol-17beta concentrations peaked on day 8 in the Ovsynch group and on day 9 in both CIDR-treated groups. The dominant follicle ovulated on day 10 in the Ovsynch group and on day 11 in both CIDR-treated groups. Thus, both CIDR-based protocols prevented premature ovulation before timed-AI in Ovsynch when the protocol was started a few days before luteolysis. This reflects the fact that progesterone levels remained high until the beef cattle were treated with PGF(2alpha).     

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.     

Timing of Ovulation and Conception Rate in Primiparous and Multiparous Cows after Synchronization of Ovulation with GnRH and PGF2α

Conception rates after Ovsynch have been higher in primiparous than in multiparous cows. The objective of this study was to investigate whether this difference might be due to differences in ovulation rate or follicular size. The experiment was conducted with 136 Holstein Frisian cows from a commercial herd in Brandenburg, Germany. All cows were synchronized using Buserelin (GnRH analogue) at day ?10, Tiaprost (PGF_2α analogue) at day ?3 and again GnRH at day ?1. Timed artificial insemination (TAI) was carried out 16–20 h after the second dose of GnRH on day 0. Milk samples for analysis of milk progesterone were obtained on days ?17, ?10, ?3 and at TAI. Progesterone concentrations were used to determine the stage of oestrus cycle at the start of the synchronization protocol and to investigate the presence of functional luteal tissue before treatment with PGF_2α and TAI. All animals were examined by ultrasound at the second treatment with GnRH, at AI, 8 and 24 h after AI. Overall synchronization rate (proportion of cows with an ovulation within 40 h after GnRH) was 86.8% in primiparous and 88.2% in multiparous cows, respectively. Ovulation occurred earlier in primparous than in multiparous cows (p < 0.05) and ovulatory follicles were smaller. Conception rates were numerically higher in primiparous cows but the difference was not significant. Cows that displayed signs of oestrus on day ?1 and received an additional AI on this day were more likely to conceive than cows that only received TAI 16 to 20 h after GnRH2. It is concluded that ovulation occurs earlier in primiparous than in multiparous cows after Ovsynch. However, a significant relationship between these differences and the probability of conception could not be established.     

Treatment of anovulatory anoestrous postpartum dairy cows with a gonadotropin-releasing hormone (GnRH), prostaglandin F2𝛂, GnRH regimen or with progesterone and oestradiol benzoate

AIM: To compare 2 treatments for anovulatory anoestrus (AA) in postpartum dairy cows. The treatments were combinations of gonadotropin-releasing hormone (GnRH) and prostaglandin F_2𝛂 (PG) or progesterone (P4) and oestradiol benzoate (ODB).

METHODS: Forty AA cows from each of 5 herds were blocked by age (2 or >2 years old) and randomly assigned to 1 of 2 treatments. The first group (GPG) were treated with 250 𝛍g of a GnRH analogue, gonadorelin, followed 7 days later by 15 mg of the PG analogue, luprostiol. Two days later the cows were injected with 250 𝛍g of gonadorelin. Cows were artificially inseminated 16–24 h after the second GnRH injection. The second group (P4+ODB) were treated with an intravaginal P4 releasing device for 6 days, followed 24 h after device removal by injection of 1 mg of ODB. Cows were pregnancy tested 35–40 days after the initial insemination and twice again at 6–8 week intervals thereafter.

RESULTS: There was no significant difference between P4+ODB and GPG groups in the percentage of cows submitted for insemination in the first 7 days (94.0% vs 100% for P4+ODB vs GPG, respectively; p>0.3), in conception rate to first insemination within the first 7 days (43.6% vs 35.0% for P4+ODB vs GPG, respectively; p>0.2), in the percentage of cows conceiving in the first 28 days of the breeding period (68.0% vs 58.3%, P4+ODB vs GPG, respectively; p>0.1), or in median interval from the end of treatment to conception (20 vs 21days;p>0.1).

CONCLUSIONS: No differences in the reproductive performance of AA cows treated with either P4+ODB or GPG were detected. However, given the small number of animals enrolled, further data are required before the GPG protocol can be recommended for treatment of AA cows.     

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.     

Comparison of effects of GnRH and prostaglandin in combination, and prostaglandin on conception rates and time to conception in dairy cows

OBJECTIVE: To assess the effectiveness of a gonadotrophin-releasing hormone (GnRH) / prostaglandin program (GnRH-PG-GnRH, Ovsynch) on conception rates and time to conception of lactating dairy cows compared with a PG program (double prostaglandin injection). DESIGN: A randomised multi-centre cohort study was conducted with 778 cows from nine dairy herds. Cows at different stages of lactation were randomly assigned, after matching for days open at the time of treatment, to either the PG or Ovsynch program. PROCEDURE: Cows on the PG program received two intramuscular injections of prostaglandin (2 mL, Prosolvin) 11 days apart. The Ovsynch program consisted of two intramuscular injections of GnRH (1 mL, Fertagyl) 9 days apart, separated by one injection of prostaglandin 40 h before the second GnRH injection. Milk samples were taken at the time of artificial insemination and assayed for progesterone by radioimmunoassay. RESULTS: The Ovsynch program was not significantly different to PG in achieving conception, with overall conception rates of 37.6% and 41.4%, respectively, for each program. There was, however, a significant interaction between the effects of parity and treatment (P = 0.03), because conception rates were higher in older cows (parity 5 or more) on the PG program than for older cows on the Ovsynch program. There was no significant effect of treatment (P > 0.5) on time to conception after treatment, but older cows were slower to conceive (P < 0.0001). Conception rates differed (P < 0.0001) among herds. CONCLUSION: The median days to conception for both groups was 22 and mean days from treatment to conception were 36.3 +/- 3.3 and 31.6 +/- 2.7 for the Ovsynch and PG programs respectively, indicating that reproductive performance of cows was not significantly different with Ovsynch program or PG program. There appears to be a need to evaluate causes of reproductive failure in older cows.     

Induction of ovulation with GnRH and PGF2alpha in lactating Bos taurus x Bos indicus cows

Induction of ovulation for timed artificial insemination (TAI) with the Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus x Bos indicus cows. Palpation per rectum and transrectal ultrasonography were used on Days -30, -20, -10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles > or = 10 mm, and every other day during treatment to determine ovarian activity. Cows were randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 microg GnRH; Day 7, 150 microg PGF2alpha; Day 9, 200 microg GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation for the first GnRH injection, detection of a corpus luteum (CL) at PGF2alpha injection, pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not effective in obtaining acceptable pregnancy rate for TAI, but it was effective for induction of cyclicity in anoestrous and lactating Bos taurus x Bos indicus cows under tropical conditions.     

The Effect of Dose and Type of Cloprostenol on the Luteolytic Response of Dairy Cattle during the Ovsynch Protocol under Different Oestrous Cycle and Physiological Characteristics

The objective of this study was to characterize the effect of dose and type of cloprostenol (CLO) on the luteolytic response of dairy cattle during the Ovsynch protocol under different oestrus cycle and physiological characteristics. Twelve non‐lactating dairy cows and 111 lactating dairy cows were used in three experiments. In Experiment I, cows were synchronized so that they had only a 5.5‐ to 6‐day‐old corpus luteum (CL) at the time of the prostaglandin F_2α (PGF_2α) treatment of Ovsynch. In Experiment II, cows were synchronized so that they had at least a CL of approximately 14 days old at the time of PGF_2α treatment and an accessory CL if they had responded to the first GnRH of Ovsynch. Furthermore, in each experiment, cows received either a standard or a double dose of d‐CLO as the luteolytic treatment. In Experiment III, lactating cows were blocked by parity and assigned to one of three luteolytic treatments during Ovsynch: 500 μg d,l‐CLO, 150 or 300 μg of d‐CLO. In Experiment I, the dose of d‐CLO had an effect (p = 0.08) on the percentage of cows with full luteolysis, but not in Experiment II (p > 0.1). More cows in Experiment II had full luteolysis than did cows of Experiment I (87% vs 58%, respectively; p = 0.007). In Experiment III, 87.1%, 84.4% and 86.2% lactating dairy cows had full luteolysis and 37.8%, 36.8% and 36.1% of cows became pregnant after treatment with 500 μg d,l‐CLO, 150 or 300 μg of d‐CLO, respectively (p > 0.05).     

An evaluation of simultaneous GnRH and cloprostenol treatment of dairy cattle with cystic ovaries

In a randomized double-blind clinical trial, 75 cows with ovarian cysts were treated with the synthetic gonadotropin releasing hormone, gonadorelin acetate (GnRH). Forty-two of these cows were simultaneously treated with cloprostenol (CP), and the remaining 33 cows received sterile saline. Milk progesterone (P₄) was measured at treatment and two days later. Clinical response 30 days after treatment was determined by palpation per rectum, and estrus and breeding dates were recorded up to 90 days after treatment. Cows were examined for pregnancy by palpation per rectum 40 days or more after breeding. Milk progesterone levels two days after treatment were significantly lower and the 30-day clinical response rate was significantly higher in the GnRH + CP group than in the GnRH group. Intervals to first estrus and to conception, proportion in heat by day 21 after treatment, and pregnancy rate by 90 days did not differ significantly between the groups. The same relationships held in a subset of cows with P₄≥1 ng/mL at treatment. Fewer cows in the GnRH + CP group became pregnant by day 90 after treatment, but this difference was not significant. These results suggest that simultaneous GnRH and cloprostenol treatment of all cows with cystic ovaries cannot be recommended at this time.     

Pregnancy Rates in Angus Cross Beef Cows Bred at Observed Oestrus With or Without Second GnRH Administration in Fixed‐Time Progesterone‐Supplemented Ovsynch and CO‐Synch Protocols

Crossbred cows (n = 1073) from five locations had oestrous cycles synchronized with 100 μg of GnRH IM and insertion of controlled internal drug release device (CIDR) on Day 0 followed by 25 mg of PGF_2α IM and CIDR removal on Day 7. Kamar^® patches were placed on all cows at CIDR removal. Cows were observed three times daily for oestrus after PGF_2α administration. In the Ovsynch‐CIDR group, cows detected in oestrus (n = 193) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 80 received and 113 did not receive a second GnRH at 48 h after PGF_2α. Cows (n = 345) not detected in oestrus received a second GnRH at 48 h after PGF_2α on Day 9, and fixed‐time AI 16 h after the GnRH on Day 10. In the CO‐Synch‐CIDR group, cows detected in oestrus (n = 224) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 79 received and 145 did not receive a second GnRH at 64 h after PGF_2α. Cows (n = 311) not detected in oestrus received a second GnRH on Day 10 at the time of AI, 64 h after PGF_2α. The AI pregnancy rates were not different between the Ovsynch‐CIDR and CO‐Synch‐CIDR groups (p = 0.48). There were no differences in the AI pregnancy rates for cows inseminated at a fixed time (p = 0.26) or at detected oestrus (p = 0.79) between the treatment groups. Among cows inseminated in oestrus, there were no differences in the AI pregnancy rates between cows that received or did not receive the second GnRH (p = 0.47). In conclusion, acceptable AI pregnancy rates can be achieved with or without inclusion of oestrus detection in the Ovsynch‐CIDR and CO‐Synch‐CIDR protocols. Among cows detected in oestrus, cows that received a second GnRH yielded similar pregnancy rates when compared with cows that did not receive the second GnRH.     

Treatment of anovulatory anoestrous postpartum dairy cows with a gonadotropin-releasing hormone (GnRH), prostaglandin F2 alpha, GnRH regimen or with progesterone and oestradiol benzoate

AIM: To compare 2 treatments for anovulatory anoestrus (AA) in postpartum dairy cows. The treatments were combinations of gonadotropin-releasing hormone (GnRH) and prostaglandin F2 (PG) or progesterone (P4) and oestradiol benzoate (ODB). METHODS: Forty AA cows from each of 5 herds were blocked by age (2 or 2 years old) and randomly assigned to 1 of 2 treatments. The first group (GPG) were treated with 250 mug of a GnRH analogue, gonadorelin, followed 7 days later by 15 mg of the PG analogue, luprostiol. Two days later the cows were injected with 250 mug of gonadorelin. Cows were artificially inseminated 16-24 h after the second GnRH injection. The second group (P4+ODB) were treated with an intravaginal P4 releasing device for 6 days, followed 24 h after device removal by injection of 1 mg of ODB. Cows were pregnancy tested 35-40 days after the initial insemination and twice again at 6-8 week intervals thereafter. RESULTS: There was no significant difference between P4+ODB and GPG groups in the percentage of cows submitted for insemination in the first 7 days (94.0% vs 100% for P4+ODB vs GPG, respectively; p>0.3), in conception rate to first insemination within the first 7 days (43.6% vs 35.0% for P4+ODB vs GPG, respectively; p>0.2), in the percentage of cows conceiving in the first 28 days of the breeding period (68.0% vs 58.3%, P4+ODB vs GPG, respectively; p>0.1), or in median interval from the end of treatment to conception (20 vs 21 days; p>0.1). CONCLUSIONS: No differences in the reproductive performance of AA cows treated with either P4+ODB or GPG were detected. However, given the small number of animals enrolled, further data are required before the GPG protocol can be recommended for treatment of AA cows.     

Effect of estrus synchronization protocols on plasma progesterone profile and fertility in postpartum anestrous Kankrej cows

The study was aimed at induction/synchronization of estrus in postpartum anestrous Kankrej cows of zebu cattle maintained at an organized farm. The study included use of different hormone protocols, viz., Ovsynch, CIDR (controlled internal drug release), Ovsynch plus CIDR, and Heatsynch with estimation of plasma progesterone on days 0, 7, 9/11 (artificial insemination--AI) and on day 20 post-AI following fixed time insemination. Thirty selected anestrous animals were divided into five equal groups (four treatment and one control), and the findings were compared with the normal cyclic control group of six cows. All the protocols were initiated in cows with postpartum anestrous period of more than 4 months, considering the day of first GnRH injection or CIDR insertion as day 0. The animals were bred by fixed time artificial insemination. Pregnancy was confirmed per rectum on day 60 post-AI in non-return cases. The conception rates at induced/first heat in Ovsynch, CIDR, Ovsynch + CIDR, and Heatsynch protocols were 33.33, 66.66, 50.00 and 16.67%, respectively. The corresponding overall conception rates of three cycles post-treatment were 50.00% (3/6), 100.00% (6/6), 66.66% (4/6), and 50.00% (3/6). In normal cyclic and anestrous control groups, the pooled pregnancy rates were 83.33% (5/6) and 16.67% (1/6), respectively. The pooled mean plasma progesterone (nanograms per milliliter) concentrations were significantly (P < 0.05) higher on day 7 in Ovsynch (5.727 ± 1.26), CIDR (4.37 ± 0.66), Ovsynch plus CIDR (3.55 ± 0.34), and Heatsynch (5.92 ± 1.11) protocols as compared with their corresponding values obtained on days 0, 9/11 (AI), and on day 20 post-AI. In anestrous control group, the mean progesterone concentration at the beginning of experiment was 0.67 ± 0.33 ng/ml, which was at par with values of all other groups. The overall plasma progesterone levels on the day of initiating treatment were low in all groups, with smooth small inactive ovaries palpated per rectum twice at 10 days interval, suggesting that most of the animals used in the study were in anestrous phase. Mean (± SE) values of plasma progesterone (nanograms per milliliter) on day 20 post-AI were higher in conceived cows than the non-conceived cows of all the groups, but differed significantly (P < 0.05) only in normal cyclic group. These results suggest that use of different hormone protocols particularly Ovsynch, CIDR, and Ovsynch + CIDR may serve as an excellent tool for induction and synchronization of estrus and improvement of conception rate in postpartum anestrous Kankrej cows.     

Factors Affecting Synchronization and Conception Rate after the Ovsynch Protocol in Lactating Holstein Cows

Objectives were to evaluate risk factors affecting ovulatory responses and conception rate to the Ovsynch protocol. Holstein cows, 466, were submitted to the Ovsynch protocol [day 0, GnRH‐1; day 7, prostaglandin (PG) F_2α; day 9, GnRH‐2] and 103 cows were inseminated 12 h after GnRH‐2. Information on parity, days in milk at GnRH‐1, body condition, milk yield, exposure to heat stress, pre‐synchronization with PGF_2α and the use of progesterone insert from GnRH‐1 to PGF_2α was collected. Ovaries were scanned to determine responses to treatments. Overall, 54.7%, 10.6%, 2.2%, 81.1%, 9.0%, 91.5% and 36.9% of the cows ovulated to GnRH‐1, multiple ovulated to GnRH‐1, ovulated before GnRH‐2, ovulated to GnRH‐2, multiple ovulated to GnRH‐2, experienced corpus luteum (CL) regression and conceived, respectively. Ovulation to GnRH‐1 was greater in cows without a CL at GnRH‐1, cows with follicles >19 mm and cows not pre‐synchronized with PGF_2α 14 days before GnRH‐1. Multiple ovulations to GnRH‐1 increased in cows without CL at GnRH‐1 and cows with follicles ≤19 mm at GnRH‐1. Ovulation before GnRH‐2 was greater in cows without CL at PGF_2α. Ovulation to GnRH‐2 increased in cows that received a progesterone insert, cows with a CL at GnRH‐1, cows with follicles not regressing from the PGF_2α to GnRH‐2, cows with larger follicles at GnRH‐2, cows that ovulated to GnRH‐1 and cows not pre‐synchronized. Multiple ovulations after GnRH‐2 increased in cows with no CL at GnRH‐1, multiparous cows and cows that multiple ovulated to GnRH‐1. Conception rate at 42 days after AI increased in cows with body condition score > 2.75 and cows that ovulated to GnRH‐2. Strategies that optimize ovulation to GnRH‐2, such as increased ovulation to GnRH‐1, should improve response to the Ovsynch protocol.     

Evaluation of three hormonal protocols for anovulatory lactating cows under regulations restricting the use of estrogenic compounds

When European Union regulations restricted the use of estrogenic compounds in food‐producing animals, refined hormonal protocols were no longer applicable for anovulatory cows. However, Ovsynch and its adaptations are routinely and uniformly applied to all cows regardless of ovarian function. To evaluate their efficacy on anovulatory cows, 143, 147 and 144 anovulatory cows received Ovsynch, Presynch and G6G protocols, respectively. In comparison, 150 cyclic cows were bred without using a synchronized protocol. Results showed that cows in the Presynch group had luteolysis responding to the last prostaglandin F_2α (PGF_2α) injection greater than the Ovsynch group. The serous progesterone levels at the first gonadotropin‐releasing hormone of Ovsych and the last PGF_2α injection was greater in the G6G group than the other two hormonal treatment groups. Concentrations of Ca²⁺ and total protein in cervical mucus in all three hormone‐treated groups before artificial insemination (AI) were significantly different from the controls. The G6G group obtained a greater pregnancy rate compared with Ovsynch and Presynch, but significantly less than the controls. For open cows in the Ovsynch group, estrus rate within 24 days after the first AI was significantly less than the controls. In conclusion, the G6G treatment resulted to better reproductive performance in anovulatory cows.     

Ovsynch Plus protocol improves ovarian response in anovular Murrah buffaloes in low‐breeding season

The objective of the study was to evaluate the efficacy of ovarian response and pregnancy rate in anovular buffaloes following Ovsynch and Ovsynch Plus protocols. Buffaloes (n = 55) were divided into two groups: Ovsynch group (n = 26): GnRH (10 μg, GnRH1) on Day 0, PGF₂α (25 mg) on Day 7, GnRH (10 μg, GnRH2) on Day 9; Ovsynch Plus group (n = 29): 500 IU equine chorionic gonadotropin (eCG) 72 hr (day ?3) prior to Ovsynch protocol, followed by fixed timed artificial insemination (FTAI) 6 and 24 hr after GnRH2 injection in bot groups. Transrectal ultrasonography was performed daily, that is, from day 0 and ?3 in Ovsynch and Ovsynch Plus group, respectively for ovarian response and pregnancy diagnosis at day 30 post‐insemination. In Ovsynch Plus group, administration of eCG prior to GnRH1 increased (p < .001) the diameter (mm) of dominant follicle (DF) from 10.15 ± 0.26 to 12.23 ± 0.34 within 72 hr of treatment resulting higher ovulatory response to GnRH1. Ovulation after GnRH1 was higher (p < .01) in Ovsynch Plus group (96.6%) than Ovsynch group (61.5%). However, ovulation rate to GnRH2 was similar (p > .05) between groups (Ovsynch group: 76.9% vs. Ovsynch Plus group: 70.0%). Mean DF diameter (mm) that ovulated to both GnRHs was higher (p < .01) than non‐ovulated counterparts in both groups (Ovsynch group: 10.80 ± 0.27 vs. 8.47 ± 0.53; Ovsynch Plus group: 11.99 ± 0.24 vs. 9.5 ± 0.63). Pregnancy was established in buffaloes which responded to both GnRHs, irrespective of groups, being higher (p = .52) in Ovsynch Plus group (34.5%) than Ovsynch group (23.1%), though non‐significant. In summary, this study showed that eCG inclusion prior to Ovsynch regimen improves ovulatory response in anovular buffaloes during low‐breeding season.     

Effect of follicular aspiration at the onset of progesterone-based timed artificial insemination on the follicular dynamics and fertility of early postpartum Japanese black cows

The effect of gonadotropin-releasing hormone analogue (GnRH-A) or follicular aspiration at the onset of progesterone-based timed artificial insemination (TAI) on subsequent follicular growth and synchronization of ovulation was examined in early postpartum Japanese Black cows. A total of 40 (22 in Exp. 1 and 18 in Exp. 2) Japanese Black cows at 20-30 days postpartum were fitted with a progesterone releasing internal device (PRID) for 7 days, injected with a prostaglandin F2α analogue upon removal of the PRID and GnRH-A 48 h later, and inseminated 18 h after GnRH-A injection. In Exp. 1, the animals were divided into three groups (untreated control, GnRH-A injection or follicular aspiration) of different treatments on the first day of PRID insertion (day 0), and the synchronized ovulation rate in the follicular aspiration group (100%; 8/8) tended to be higher (P = 0.077) than that in the control group (42.9%; 3/7). In Exp. 2, follicular growth in the GnRH (n = 9) and follicular aspiration (n = 9) groups was monitored by ultrasonography. Four out of the nine animals in the GnRH group had a corpus luteum on either day 4 or day 7 (OV group), and the other five animals had no induced ovulation (NOV group). The diameter of the ovulatory follicle on day 9 in the OV group (1.44 ± 0.11 cm) tended to be greater (P = 0.078) than that in the NOV group (1.13 ± 0.07 cm). Follicular aspiration at the onset of PRID-based TAI of early postpartum Japanese Black cows, regardless of the resumption of ovarian cyclicity, tended to result in a higher rate of synchronization of ovulation than that of the untreated controls.     

Reproductive efficiency in grazing lactating dairy cows under a programmed reproductive management system

OBJECTIVE: To evaluate the effectiveness of a reproductive management program consisting of combinations of Ovsynch/TAI and prostaglandin (PG) F(2alpha) treatments in Holstein dairy cows under a pasture-based dairying system. DESIGN: Field trial. PROCEDURE: A total of 1177 cows in 8 commercial dairy farms were randomly allocated to control and treatment groups. Treatment group cows received one of two interventions depending upon the number of days postpartum (DPP) before the planned start of breeding. Cows more than 50 DPP by the planned start of breeding received the Ovsynch/TAI treatment, consisting of gonadotrophin releasing hormone (GnRH) - PGF(2alpha)- GnRH plus timed artificial insemination. Cows between 40 and 50 DPP received a PGF(2alpha) treatment followed by oestrus detection and, if the cow was not seen in oestrus, the cow received a second PGF(2alpha) 14 days later. Control cows were submitted to twice a day heat detection followed by artificial insemination. The experimental period was the start of the breeding season plus 21 days for cows over 50 DPP at the start of breeding, and was 40-61 DPP for cows that calved later and passed their voluntary waiting period after the start of the breeding season. RESULTS: Submission rate was higher for the treated group than for the control group (84.9% vs. 55.1%; P < 0.0001), as was the conception rate (51.0% vs. 46.1%; P < 0.03). Due to farm variations, pregnancy rate was similar in both groups (38.5% vs. 28.2%; P > 0.1). Within the treated group, conception rate and pregnancy rate of the cows inseminated after a PGF(2alpha) were higher than for timed artificial inseminated cows (51.4% vs. 32.6%; P < 0.001), and (37.8% vs. 32.6%; P < 0.001). CONCLUSION: A programmed reproductive management protocol may improve reproductive efficiency in dairy farms with seasonal breeding, by increasing submission and conception rates at the beginning of the breeding season and/or at the end of the voluntary waiting period. Fertility of cows bred after a PGF(2alpha) synchronised heat was greater than after an Ovsynch/TAI protocol.     

Comparison of Oestrous Intensity between Natural Oestrus and Oestrus Induced with Ovsynch Based Treatments in Japanese Black Cows

The aim of this study was to examine the possible differences of oestrous intensity between natural oestrus and induced oestrus using the walking activity measuring device. Walking activity was used as an evaluation index of oestrous intensity. A total of 27 Japanese Black cows, more than 40 days after calving and clinically normal, were randomly assigned to three groups. Walking activity was recorded using a commercially available computerized pedometer system. The treatment groups consisted of an Ovsynch (n = 8) and a controlled internal drugs releasing device (CIDR) + Ovsynch (n = 9) group. The control group (n = 10) received no treatment. Walking activity was examined in all groups. Timed artificial insemination (timed AI) was performed at 16 hours after the onset of oestrus in the control group and at 24 h after second administration of GnRH in the treatment groups. Duration of oestrus had a tendency to be shorter in both the Ovsynch and the CIDR + Ovsynch groups when compared with the control group. The time required from the onset of oestrus to the time showing the highest number of steps of walking (the time to peak) showed a tendency to be shorter in CIDR + Ovsynch group. The number of steps of walking at peak and overall walking activities were significantly lower in both treatment groups than in the control group. Both activity and super-activity periods of time in the treatment groups were shorter than the control group. No difference was observed in the conception rate between the control (50.0%; 10/20), Ovsynch (50.0%; 4/8) and CIDR + Ovsynch groups (66.7%; 6/9). This study demonstrates that the oestrous intensity of cows in oestrus was different between natural oestrus and induced oestrus and also between the methods of the synchronization, but no difference was observed in the conception rate among the three groups.