• Korean Journal of Veterinary Research
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• v.63 no.2
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• pp.14.1-14.4
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• 2023

This study evaluated the effect of resynchronization programs on pregnancies in dairy cows. Of 1,342 cows confirmed not pregnant after their first artificial insemination (AI), those with a corpus luteum (CL) were resynchronized using Ovsynch or PG-GnRH-Ovsynch and those without a CL were resynchronized using GnRH-Ovsynch or modified Double-Ovsynch. There were no differences (p > 0.05) in the pregnancies per AI either between the Ovsynch (31.3%) and PG-GnRH-Ovsynch (34.0%) or between the GnRH-Ovsynch (38.7%) and modified Double-Ovsynch (39.5%). In conclusion, Ovsynch and GnRH-Ovsynch programs could be preferred to resynchronize cows with and without a CL, respectively, from the perspective of reducing costs and labor.

• Journal of Veterinary Clinics
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• v.33 no.4
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• pp.200-204
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• 2016

This study investigated whether presynchronization with GnRH 6 days before initiation of the Ovsynch program improved reproductive outcomes in dairy cows. Additionally, postponement of initiation of the Ovsynch program for cows during the metestrus phase by 5 days was investigated to determine if it improved reproductive outcomes. To accomplish this, 941 Holstein dairy cows with unknown estrous cycle were randomly allocated into an Ovsynch group (n = 768; $100{\mu}g$ gonadorelin [a GnRH analogue], $500{\mu}g$ of cloprostenol [$PGF_{2{\alpha}}$ analogue] seven days later, $100{\mu}g$ gonadorelin 56 h later and timed artificial insemination [AI] 16 h after) and a G6-Ovsynch (n = 173) that received $100{\mu}g$ GnRH followed by the Ovsynch program 6 days later. Additionally, 272 dairy cows with known estrous cycle (metestrus stage) received the Ovsynch 5 days later (Day 5-Ovsynch group, n = 272). The odds ratio (OR) for pregnancy was analyzed by logistic regression using the LOGISTIC procedure in SAS. The treatment group (p < 0.001) and AI season (p < 0.05) significantly affected the probability of pregnancy, whereas farm, cow parity, calving to AI interval, and body condition score had no affect (p > 0.05). The Day 5-Ovsynch group had a higher probability of pregnancy (OR: 1.71) than the Ovsynch group, while that of the G6-Ovsynch group was intermediate (p > 0.05). Cows inseminated during winter had a higher OR (1.39) than those inseminated during spring. Overall, additional GnRH treatment 6 days before the Ovsynch did not improve reproductive outcomes, whereas postponement of the initiation of Ovsynch by 5 days for cows during metestrus improved reproductive outcomes.

• Animal Bioscience
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• v.36 no.4
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• pp.591-600
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• 2023

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 F_2α (PGF_2α) 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, PGF_2α 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.

• Reproductive and Developmental Biology
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• v.30 no.3
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• pp.225-228
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• 2006

This study was undertaken to investigate the effect of ovulation-synchronization(OVSYNCH) method on conception rate after insemination of dairy cattle. The proportion of conception of normal fertility cows(65%) was higher than that in infertility cows(50%) in dairy cows with OVSYNCH treatment. However, there was no significant difference between experimental groups. In another experiment, when the OVSYNCH method was adapted in multiparous dairy cows, the conception rate of experimental group of $30{\sim}35kg/day$ in milk yield was significantly higher than those in groups of $20{\sim}25kg/day$ in milk yield(p<0.05). In conception rates by OVSYNCH method in experimental groups with different parity, the group of 1st parity was significantly higher than in 3rd parity group(p<0.05). The results suggest that conception rate by OVSYNCH method was affected by various reproductive conditions in dairy cattle, and OVSYNCH method could be used to increase the conception rate for infertility cows with hormone disorder.

• Journal of Veterinary Clinics
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• v.27 no.4
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• pp.397-401
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• 2010

This study was to evaluate the usefulness of a programmed reproductive management including Presynch-Ovsynch-Resynch protocol in lactating dairy cows. Nine hundred and thirty four cows calved during February to May 2008 were used for this study. Cows received im injections of 25 mg $PGF_{2{\alpha}}$ at $45{\pm}3$ and $59{\pm}3$ days in milk (DIM). Fourteen days later, Ovsynch was initiated with an im injection of $100\;{\mu}g$ GnRH ($73{\pm}3$ DIM), 25 mg $PGF_{2{\alpha}}$ 7 days later ($80{\pm}3$ DIM), $100\;{\mu}g$ GnRH 56 h later and timed artificial insemination (TAI) 16 h after the GnRH injection. Cows showed estrus during the Presynch-Ovsynch, were inseminated artificially according to am-pm rule. Pregnancy was determined on 32 days after AI using ultrasonography. Cows diagnosed pregnant were re-examined for pregnancy by rectal palpation at 60 days after AI. Non-pregnant cows were resynchronized by receiving $100\;{\mu}g$ GnRH, 25 mg $PGF_{2{\alpha}}$ 7 days later, $100\;{\mu}g$ GnRH 56 h later and TAI 16 h after. Cows with estrus since the first AI before the completion of Resynch protocol were also inseminated artificially according to am-pm rule. Pregnancy was determined by the same manner as following the first AI. Fifty five percents of the cows treated showed estrus and received AI before completion of the Presynch-Ovsynch protocol, while 45% received TAI, regardless of estrus exhibition following the completion of the protocol. The pregnancy rate following the first AI was higher in cows that showed estrus and received AI (43.3 and 38.5%) during the Presynch-Ovsynch than cows with TAI (34.6 and 29.6%) on 32 and 60 days after AI (P < 0.01). Sixty six percents of cows diagnosed non-pregnant following the first AI showed estrus before the completion of Resynch protocol and received AI, while 34% received TAI, regardless of estrus exhibition following the completion of the protocol. The pregnancy rate following the second AI was higher in cows that showed estrus before the completion of Resynch protocol and received AI (40.2 and 36.8%) than cows with TAI (21.2 and 18.2%) on 32 and 60 days after AI (P < 0.01). The cumulative pregnancy rates following the first and second AIs were 60.8 and 53.9% on 32 and 60 days after AI, respectively. These data suggest that inclusion of Presynch-Ovsynch-Resynch protocol and estrus detection into the programmed reproductive management might be an alternative option to control dairy cattle breeding.

• Journal of Veterinary Clinics
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• v.37 no.5
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• pp.235-241
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• 2020

We aimed to determine the effect of timed artificial insemination (TAI) protocols on the pregnancy rate per insemination and pregnancy loss compared with AI performed at detected estrus in dairy cows and Korean Hanwoo cattle under heat stress. In dairy cattle, 1,250 sets of data that underwent AI during heat stress (temperature-humidity index ≥ 72) were categorized according to their TAI protocols or as controls: 1) PGF_2α-36 h-estradiol benzoate (EB)-36 h-TAI (PG-EB group, n = 113); 2) GnRH-7 days-PGF_2α-56 h-GnRH-16 h-TAI (Ovsynch group, n = 455); or 3) GnRH-6 days-Ovsynch (G6G group, n = 136). The remaining cows underwent AI at detected estrus (AIDE group, n = 546). The probability of pregnancy per AI 45 days after AI was higher (P < 0.01) in the PG-EB (odds ratio [OR]: 1.68), Ovsynch (OR: 1.48), and G6G (OR: 1.79) groups than in the AIDE group. However, the prevalence of pregnancy loss between 30 and 45 days after AI did not differ among the groups. In Hanwoo cattle, 617 sets of data inseminated artificially under heat stress were categorized into AIDE (n = 281), PG-EB (n = 194), and combined Ovsynch or G6G (n = 142) groups. The probability of pregnancy per AI 45 days after AI and the prevalence of pregnancy loss between 30 and 45 days after AI did not differ among the groups. Thus, implementation of a TAI protocol (PG-EB, Ovsynch, or G6G) in dairy cows under heat stress improves the pregnancy rate per AI versus AIDE, whereas there is no beneficial effect of TAI on the pregnancy rate of Hanwoo cattle under heat stress.

• Journal of Veterinary Clinics
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• v.40 no.3
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• pp.238-241
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• 2023

This study determined the effect of ovarian status at the beginning of the modified Double-Ovsynch program on reproductive performance in dairy cows. In the study, 1,302 cows were treated with a modified Double-Ovsynch program at 56 days after calving. This program comprises administering gonadotropin-releasing hormones (GnRH), prostaglandin F_2α (PGF_2α) 10 days later, GnRH 3 days later, GnRH 7 days later, and GnRH 56 h later, followed by timed artificial insemination (TAI) 16 h later. At the beginning of the program, cows were categorized according to the size of the largest follicle and the presence of a corpus luteum (CL) in the ovaries as follows: 1) small follicle (<5 mm, SF group, n = 100), 2) medium follicle (8-20 mm, MF group, n = 538), and 3) large follicle (≥25 mm, LF group, n = 354) without a CL, or 4) the presence of a CL (CL group, n = 310). The pregnancies per AI after the first TAI were analyzed by logistic regression using the LOGISTIC procedure, and the logistic model included the fixed effects of the herd size, parity, body condition score (BCS) at the first TAI, TAI period, and ovarian status. A larger herd size, higher BCS at the first TAI, and TAI period with no heat stress increased (p < 0.05) the probability of pregnancy per AI after the first TAI. However, ovarian status at the beginning of the program did not affect (p > 0.05) the pregnancies per AI (ranges of 37.9% to 42.9%). These results show that the modified Double-Ovsynch program can be used effectively while maintaining good fertility regardless of the ovarian status in dairy herds.

• Journal of Embryo Transfer
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• v.26 no.2
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• pp.105-109
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• 2011

Ovulation synchronization (ovsynch) has proved to increase the number of insemination in cattle by overcoming the problems of heat detection. The aim of this study was to do ovsynch in water buffaloes where heat detection is a major reproductive problem and to determine the conception rates after timed artificial insemination (TAI). Twenty cyclic buffaloes at ${\geq}$ 60 days postpartum were selected by examining 24 unobserved estrus buffaloes based on milk progesterone assay (progesterone concentration ${\geq}$ 1.0 ng/ml) from the Mymensingh district of Bangladesh. Ovsynch treatment regimen was started irrespective of the stage of estrous cycle. Gonadorelin (500 ${\mu}g$) was injected intramuscularly at Day 0 followed by Alfaprostol (8 mg) at Day 7. A second injection of Gonadorelin was given at Day 9 and TAI was done with frozen semen from Mediterranean buffalo bulls at 16~20 hours of the second Gonadorelin injection. Milk progesterone ELISA at Day 10~12 post AI confirmed ovulation in 16 out of 20 (80%) buffaloes (progesterone concentration ${\geq}$ 1.0 ng/ml). High progesterone concentration (${\geq}$ 1.0 ng/ml) at Day 10~12 and Day 22~24 of AI showed pregnancy in six out of 20 (30%) buffaloes. Pregnancy was further confirmed by ultrasonography at Day 40 in these six buffaloes. In conclusion, ovsynch followed by TAI could be applied in cyclic buffaloes for overcoming the estrus detection problems; however, more studies are needed to increase the conception rate.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.159-163
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• 2017

The artificial insemination (AI) is one of the best assisted reproductive technologies for increasing reproductive capacity and facilitating the genetic improvement in farm animals. AI has been used in Uganda for over 60 years, but a small population of the total herd has been used. This study was conducted to investigate the efficacy of AI with estrus synchronization technique and to propose ways of improving the productivity of dairy farms through AI services in Uganda. In total, 78 cows from 11 dairy farms were selected for timed-AI. Synchronization was performed according to the ovsynch programs followed by AI using frozen semen from Korean Holstein (0.5 ml straws). Pregnancy rate was varying among farms (0-50%) and the overall pregnancy rate was 28.2%. Cows in luteal phase at the time of treatment was 40.0% whereas that in follicular phase was 20.8%. After treatment, cows that showed normal estrus signal were 45.5% (25/55). Abnormal estrus was categorized into pre-estrus (9.1%), cystic ovaries (21.8%), anestrus (18.2%) and delayed ovulation (5.5%), respectively. These results imply that an assured protocol for timed-AI should be developed to improve the productivity of dairy farms through AI services in Uganda.

• Journal of Veterinary Clinics
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• v.31 no.5
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• pp.382-388
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• 2014

The objective of this study was to determine the risk factors associated with pregnancy following 3 synchronization protocols in dairy cows. Data were collected on 1,952 cows from 22 dairy farms, including synchronization protocols ($PGF_{2{\alpha}}$ + estradiol benzoate [PG+EB], Ovsynch, and CIDR-ovsynch), cow parity, body condition score (BCS), and dates of previous calving, insemination and conception. The odds ratio (OR) for pregnancy were analyzed by logistic regression using the LOGISTIC procedure in SAS. The analysis revealed that farm (p = 0.005), cow parity (p = 0.0001), BCS (p < 0.005), and AI season (p < 0.05) significantly affected and calving to AI interval tended to affect (p < 0.1) the probability for pregnancy. Although synchronization protocols did not affect the probability for pregnancy (p > 0.05), cow parity and synchronization protocols showed a significant interaction (p < 0.005); the OR (0.60) was significantly lower (p < 0.0001) for multiparous cows compared to primiparous cows using PG+EB, whereas the OR (1.44) tended to be higher (p < 0.1) for multiparous cows compared to primiparous cows using the Ovsynch, and the probability for pregnancy did not differ between multiparous and primiparous cows using the CIDR-ovsynch (p > 0.05). Cows with BCS ${\geq}$ 3.00 were more likely pregnant (OR: 1.41) compared with cows having BCS ${\leq}$ 2.75, whereas cows inseminated during summer had a lower OR (0.73) compared with those inseminated during spring. Cows with a calving to AI interval > 150 days were more likely to be pregnant (OR: 1.20) compared with cows with a calving to AI interval ${\leq}$ 150 days. In conclusion, the OR for pregnancy following synchronization protocols in dairy cows was affected by farm, parity, BCS, calving to AI interval of the cow, and AI season, and there was a significant interaction between cow parity and synchronization protocols; the OR for pregnancy was lower for multiparous cows compared with primiparous cows using the PG+EB protocol.