Pregnancy rates in dairy cows following the administration of a GnRH analogue at the time of artificial insemination or at mid-cycle post insemination

Ryan, David P.; Kopel, E.; Boland, M.P.; Godke, R.A.

doi:10.1016/0093-691x(91)90465-p

Cited by 17 publications

(9 citation statements)

References 25 publications

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“…Especially, the plasma P4 levels in parous ewes treated with GnRH declined immediately after treatment to Day 22 (data not shown). Many authors reported that GnRH treatment reduced plasma P4 concentration [23][24][25][26], and the present result has supported this phenomenon (Fig. 1).…”

Section: Discussionsupporting

confidence: 81%

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Ishida

Okada

Sebata

et al. 1999

Journal of Reproduction and Development

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Abstract.Two experiments were conducted to enhance the corpus luteum (CL) function for increasing lambing rate of ewes treated with GnRH or hCG after artificial insemination (AI) during the non-breeding season. Ewes (Experiment 1: n=102, Experiment 2: n=37) were pretreated with a controlled internal drug release dispenser (CIDR) for 12 days and 500 IU equine chorionic gonadotropin (eCG) 1 day before CIDR removal. In Experiment 1, the ewes were treated on Day 12 (Day 0=CIDR removal): 1) Group I; GnRH (100 µg), 2) Group II; hCG (500 IU), 3) Group III; 0.6% saline (2 ml) for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups. But, there was significant (P<0.01) difference in the lambing rate between parous (27%) and non-parous (72%) in Group I. On Day 17, plasma progesterone (P4) levels of Group I were significantly (P<0.01) lower than those of Group III, but on the contrary, the plasma P4 levels of Group II were significantly (P<0.01) higher than those of Group III. In Experiment 2, the ewes were treated: 1) Group I; hCG (500 IU) on Day 6, 2) Group II; hCG (500 IU) on Day 9, 3) Group III; no treatment for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups, but on Days 12 and 15, the plasma P4 levels of Groups I and II were significantly (P<0.01) higher than those of Group III. The present results indicate that a single hCG treatment on Days 6, 9 and 12 after CIDR removal stimulates CL and increased P4 concentration, but the increased P4 levels did not reflect on the fertility of treated ewes.

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Section: Discussionsupporting

confidence: 81%

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Ishida

Okada

Sebata

et al. 1999

Journal of Reproduction and Development

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“…2 TAI = timed AI; CL = corpus luteum; P 4 = plasma progesterone. injection of 100 μg of GnRH 7 d before the resynchronization protocol initiation induced ovulation of follicles ≥10 mm in diameter, resulting in the formation of a new CL (Ryan et al 1991). Moreover, GnRH can directly affect follicle development by downregulating the expression of aromatase in granulosa cells, reducing the secretion of estradiol by the dominant follicle (Fitzpatrick et al, 1997), thereby inhibiting estrus expression.…”

mentioning

confidence: 99%

Effect of an Ovsynch56 protocol initiated at different intervals after insemination with or without a presynchronizing injection of gonadotropin-releasing hormone on fertility in lactating dairy cows

Bruno

Moraes

Hernández-Rivera

et al. 2014

Journal of Dairy Science

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The objectives of this study were to evaluate effects of 2 resynchronization protocols beginning at different intervals after artificial insemination (AI) on the pattern of return to estrus, ovarian responses, and pregnancy per AI (P/AI) to reinsemination. Lactating cows from 2 dairies, located in Texas (n=2,233) and Minnesota (n=3,077), were assigned to 1 of 4 timed AI (TAI) protocols 17 ± 3 d after AI. All cows were examined for pregnancy 31 ± 3 d after previous AI. Cows assigned to early Ovsynch56 (E-OV56) or OV56 received the Ovsynch56 protocol starting 24 or 31 d after AI, respectively. Cows assigned to early GnRH-GnRH-PGF(2α)-GnRH (E-GGPG) or GGPG received a presynchronizing GnRH injection 17 or 24 d after AI, respectively, 7 d before the start of the Ovsynch56 protocol. Cows observed in estrus after enrollment were inseminated on the same day. Ovaries were examined and blood was sampled for progesterone concentration on the day of first GnRH and PGF(2α) injection of the Ovsynch56 protocol. Pregnancy was diagnosed at 31 and 66 d after resynchronized AI. On the day of the first GnRH injection of the TAI, a higher percentage of cows on E-GGPG and GGPG protocols had a corpus luteum (E-GGPG=83.8, GGPG=91.2, E-OV56=80.4, and OV56=75.5%) and progesterone concentration >1 ng/mL (E-GGPG=62.5, GGPG=76.0, E-OV56=53.6, and OV56=60.8%) than cows assigned to other protocols. However, the percentage of cows ovulating to the first GnRH injection of TAI was not affected by treatment. Fewer E-GGPG and more OV56 cows were reinseminated in estrus (E-GGPG=23.7, GGPG=49.0, E-OV56=41.6, and OV56=57.6%). Treatment did not affect P/AI at 31 or 66 d for cows reinseminated in estrus. However, cows reinseminated in estrus had greater P/AI at 31 (40.0 vs. 27.5%) and 66 d (36.0 vs. 23.9%) than cows completing the TAI protocols. Among cows completing the TAI protocols, initiation of GGPG at 24 d after AI increased, whereas initiation of Ovsynch56 at 24 d after AI decreased P/AI at 31 d after reinsemination (E-GGPG=30.6, GGPG=28.3.0, E-OV56=22.3, and OV56=28.7%). Pregnancy per AI did not differ across treatment at 66 d after TAI (E-GGPG=26.6, GGPG=24.4, E-OV56=20.0, and OV56=24.1%). Overall, type of resynchronization protocol and protocol initiation time did not affect P/AI 66 d after reinsemination (E-GGPG=29.7, GGPG=30.5, E-OV56=26.1, and OV56=30.4%). In conclusion, GGPG resynchronization protocols and initiation of resynchronization protocol 24 d after AI reduced the number of cows reinseminated in estrus but neither the timing of initiation of resynchronization nor presynchronization with GnRH affected overall P/AI.

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“…Furthermore, presynchronizing the estrous cycle of cows with GnRH resulted in a greater percentage of cows ovulating in response to the GnRH injection given on d 0, which resulted in greater percentage of cows bearing a CL on d 7. It is likely that the presynchronizing injection of GnRH given 7 d before the start of the resynchronization protocol induced ovulation in cows bearing follicles ≥10 mm in diameter that resulted in the formation of a new CL and the recruitment of a new follicular wave approximately 36 to 60 h later (Ryan et al, 1991;Pursley et al, 1995). This would have resulted in GGPG cows starting the resynchronization protocol at approximately d 7 of the estrous cycle.…”

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confidence: 99%

Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnancy rates and ovarian responses

Dewey

Mendonça

Lopes

et al. 2010

Journal of Dairy Science

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Objectives were to evaluate 3 resynchronization protocols for lactating dairy cows. At 32+/-3 d after pre-enrollment artificial insemination (AI; study d -7), 1 wk before pregnancy diagnosis, cows from 2 farms were enrolled and randomly assigned to 1 of 3 resynchronization protocols after balancing for parity, days in milk, and number of previous AI. All cows were examined for pregnancy at 39+/-3 d after pre-enrollment AI (study d 0). Cows enrolled as controls (n=386) diagnosed not pregnant were submitted to a resynchronization protocol (d 0-GnRH, d 7-PGF2alpha, and d 10-GnRH and AI) on the same day. Cows enrolled in the GGPG (GnRH-GnRH-PGF2alpha-GnRH) treatment (n=357) received a GnRH injection at enrollment (d -7) and if diagnosed not pregnant were submitted to the resynchronization protocol for control cows on d 0. Cows enrolled in CIDR treatment (n=316) diagnosed not pregnant received the resynchronization protocol described for control cows with addition of a controlled internal drug release (CIDR) insert containing progesterone (P4) from d 0 to 7. In a subgroup of cows, ovaries were scanned and blood was sampled for P4 concentration on d 0 and 7. After resynchronized AI, cows were diagnosed for pregnancy at 39+/-3 and 67+/-3 d (California herds) or 120+/-3 d (Arizona herds). Cows in the GGPG treatment had more corpora lutea than CIDR and control cows on d 0 (1.30+/-0.11, 1.05+/-0.11, and 1.05+/-0.11, respectively) and d 7 (1.41+/-0.14, 0.97+/-0.13, and 1.03+/-0.14, respectively). A greater percentage of GGPG cows ovulated to GnRH given on d 0 compared with CIDR and control cows (48.4, 29.6, and 36.6%, respectively), but CIDR and control did not differ. At 39+/-3 d after resynchronized AI, pregnancy per AI (P/AI) was increased in GGPG (33.6%) and CIDR (31.3%) cows compared with control (24.6%) cows. At 67 or 120+/-3 d after resynchronized AI, P/AI of GGPG and CIDR cows was increased compared with control cows (31.2, 29.5, and 22.1%, respectively). Presynchronizing the estrous cycle of lactating dairy cows with a GnRH 7 d before the start of the resynchronization protocol or use of a CIDR insert within the resynchronization protocol resulted in greater P/AI after resynchronized AI compared with control cows.

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Pregnancy rates in dairy cows following the administration of a GnRH analogue at the time of artificial insemination or at mid-cycle post insemination

Cited by 17 publications

References 25 publications

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Effect of an Ovsynch56 protocol initiated at different intervals after insemination with or without a presynchronizing injection of gonadotropin-releasing hormone on fertility in lactating dairy cows

Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnancy rates and ovarian responses

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