Use Of GnRH Research Articles

351 A COMPARISON OF 2 APPROACHES FOR THE USE OF GnRH TO SYNCHRONIZE FOLLICLE WAVE EMERGENCE FOR SUPEROVULATION

Although oestradiol has been used successfully to synchronize follicle wave emergence for superovulation, it cannot be used in many countries. Attention has turned to alternatives, including the use of GnRH to induce ovulation of a dominant follicle, which will be followed by emergence of a new follicular wave in 1 to 2 days. However, GnRH synchronizes follicular wave emergence only when it induces ovulation and administration of GnRH at random stages of the oestrous cycle results in ovulation in less than 60% of animals. The objective of the study was to compare superovulatory response and ova/embryo production following synchronization of follicle wave emergence for superovulation with GnRH administered 2 days after insertion of a progestin device, with a protocol in which GnRH is administered 7 days after administration of prostaglandin F2α and a progestin device. Beef donors of various breeds were placed at random into 1 of 2 groups and superstimulated by replicate so that one cow in each group had ova/embryos collected on the same day. Sixty-six superstimulations were performed in this study; 26 were performed in 13 donors that were superstimulated twice in a crossover design, and 40 donors were superstimulated once (i.e. 20 donors in each treatment group). Cows in group 1 received CIDR devices (Zoetis Animal Health, USA) on Day –2 and 100 μg of GnRH (Cystorelin, Merial USA) on Day 0; FSH treatments were initiated on Day 2 with 288 mg of Folltropin-V (Vetoquinol, Canada) given in twice-daily decreasing doses for 4 days. Prostaglandin F2α (PGF; 35 mg dinoprost, Lutalyse, Zoetis) was given with the last 2 injections of Folltropin-V and CIDR were removed with the last Folltropin-V administration (i.e. Day 6). Donors received a second GnRH at the onset of oestrus and were AI 8 and 20 h later. Donors that were still in standing oestrus at the second AI were AI again at 30 h. Ova/embryo collections were done on Day 14 and embryos were classified according to the IETS manual. Cows in group 2 received an injection of PGF and a CIDR on Day –7 and 100 μg of GnRH on Day 0; FSH treatments were initiated on Day 2 and the remainder of the treatment protocol was as in group 1. Data (total ova/embryos collected and transferable embryos) were analysed by ANOVA for mixed models, using treatment as a fixed variable and cow (i.d.) as a random variable. The group 1 cows produced a mean (± s.e.m.) of 18.6 ± 1.9 total ova/embryos of which 12.7 ± 1.5 were of transferable quality (7.2 ± 1.3 grade 1). Cows in group 2 produced a mean (± s.e.m.) of 19.5 ± 1.7 total ova/embryos, of which 14.8 ± 1.5 were of transferable quality (8.9 ± 1.2 grade 1). Although 2 more transferable embryos were obtained in group 2, differences were not significant (P > 0.3). At the same time as this experiment was done, 214 other cows were superstimulated in this practice, yielding an average of 7.9 transferable embryos per donor. Results suggest that both approaches are efficacious for the superstimulation of beef cows.Special thanks to Vetoquinol/Bioniche Animal Health, USA for support.

Resynchronization with unknown pregnancy status using progestin-based timed artificial insemination protocol in beef cattle

Two experiments were designed to evaluate the use of resynchronization (RESYNCH) protocols using a progestin-based timed artificial insemination (TAI) protocol in beef cattle. In experiment 1, 475 cyclic Nelore heifers were resynchronized 22 days after the first TAI using two different inducers of new follicular wave emergence (estradiol benzoate [EB; n = 241] or GnRH [n = 234]) with the insertion of a norgestomet ear implant. At ear implant removal (7 days later), a pregnancy test was performed, and nonpregnant heifers received a dose of prostaglandin plus 0.5 mg of estradiol cypionate, with a timed insemination 48 hours later. The pregnancy rate after the first TAI was similar (P = 0.97) between treatments (EB [41.9%] vs. GnRH [41.5%]). However, EB-treated heifers (49.3%) had a greater (P = 0.04) pregnancy per AI (P/AI) after the resynchronization than the GnRH-treated heifers (37.2%). In experiment 2, the pregnancy loss in 664 zebu females (344 nonlactating cows and 320 cyclic heifers) between 30 and 60 days after resynchronization was evaluated. Females were randomly assigned to one of two groups (RESYNCH 22 days after the first TAI [n = 317] or submitted only to natural mating [NM; n = 347]). Females from the NM group were maintained with bulls from 15 to 30 days after the first TAI. The RESYNC-treated females were resynchronized 22 days after the first TAI using 1 mg of EB on the first day of the resynchronization, similar to experiment 1. No difference was found in P/AI (NM [57.1%] vs. RESYNC [61.5%]; P = 0.32) or pregnancy loss (NM [2.0%] vs. RESYNC [4.1%]; P = 0.21) after the first TAI. Moreover, the overall P/AI after the RESYNCH protocol was 47.5%. Thus, the administration of 1 mg of EB on day 22 after the first TAI, when the pregnancy status was undetermined, promotes a higher P/AI in the resynchronized TAI than the use of GnRH. Also, the administration of 1 mg of EB 22 days after the TAI did not affect the preestablished pregnancy.

Timed insemination of beef heifers using the 7–11 Synch protocol1

Two experiments were conducted over 3 yr to determine pregnancy rates in beef heifers after a timed AI in response to the 7-11 Synch protocol. In Exp. 1, 179 heifers were either fed melengestrol acetate (MGA; 7-11 Synch) or given an intravaginal progesterone (P4)-releasing insert [controlled intravaginal drug releasing device (CIDR); 7-11 CIDR] for 7 d. Prostaglandin F2αwas administered on the last day of MGA feeding or at CIDR removal followed by the CO-Synch protocol (GnRH-PGF2α-GnRH) beginning 4 d after MGA withdrawal or 2 d after CIDR removal. Heifers received a timed AI with GnRH beginning 48 h after the second PGF2α. Blood samples were collected at d -10, 0 (start of MGA feeding), and 18 (second PGF2α injection). In Exp. 2, 298 beef heifers were treated with the 7-11 Synch protocol with (7-11 Synch) or without (7 Synch) the first GnRH injection. Fixed time AI and GnRH was given 54 h after PGF2α. Blood samples were collected at d -10 and 0 in yr 1 and d -10, 0, 18 and at AI in yr 2. In Exp. 1, no differences were detected between 7 and 11 Synch and 7-11 CIDR for attainment of puberty in noncyclic heifers (94 vs. 78%; P = 0.21), the proportion of heifers that had luteal tissue on d 18 (87 vs. 83%; P = 0.41), or pregnancy rates after timed AI (47 vs. 46%; P = 0.99). In Exp. 2, administration of GnRH 4 d after the last MGA (7-11 Synch) feeding tended (P = 0.07) to induce more prepubertal heifers to cycle (88 vs. 61%) and increased (P < 0.01) the proportion of heifers with luteal tissue on d 18 (88 vs. 72%) compared with heifers in the 7 Synch treatment. Pregnancy rates after the 54 h timed AI were greater (P < 0.01) in the 7-11 Synch treatment (55%) than in the 7 Synch (38%). We conclude that heifer pregnancy rates did not differ whether feeding MGA for 7 d or applying a CIDR insert for 7 d before a CO-Synch protocol. In contrast, use of GnRH at the beginning of the CO-Synch protocol improved pregnancy rates after a timed AI by inducing more prepubertal heifers to ovulate and increasing the proportion of heifers with luteal tissue at the PGF2α injection.

Effect of synchronization protocols and GnRH treatment on the reproductive performance in goats

Experiment 1 was designed to determine if the estrous response and pregnancy rates differ between two synchronization protocols (Ovsynch vs two PGF2α injections, 10 days apart), in Beetal and Dwarf does. The Ovsynch group of goats (n=14) received an intramuscular injection of a GnRH analogue (12.5μg lecirelin) on day 0 and a treatment of a PGF2α analogue (37.5μg d-cloprostenol), on day 7 – followed by a second injection of the GnRH analogue 48h later (day 9). The double PGF-treated goats (n=14) received two intramuscular injections of a PGF2α analogue 10 days apart. The estrous response did not differ significantly between the regimes (Ovsynch 71%; double PGF 100%). Further, the interval from standing estrus to ovulation (24±3.7h vs 30±2.7h), ovulatory diameter (7.1±0.2mm vs 7.0±0.2mm), pregnancy rate (60% vs 78%) and fecundity (1.6±0.5 vs 1.6±0.7) was not significantly different between the Ovsynch and PGF treatment groups. The objective of Experiment 2 was to determine if the administration of GnRH at the time of natural breeding increases the pregnancy rate in Beetal goats. Goats were randomly allocated to two groups (GnRH, n=11 and Control, n=14). The GnRH-treated does received 12.5μg lecirelin on the day of natural breeding, while the control does received no treatment. The interval from standing estrus to ovulation (31.2±2.9h vs 36.0±5.3h; P>0.05), ovulatory follicle diameter (6.7±0.1mm vs 7.2±0.5mm; P<0.05), pregnancy rate (54% vs 64%; P>0.05) and fecundity (1.5±0.5 vs 1.7±0.5; P>0.05) were evaluated for the GnRH and control does, respectively. It could be concluded that the Ovsynch treatment appeared to be similar to the double PGF protocol in terms of the reproductive response. However, this needs to be tested on a larger herd size. Furthermore, it would seem that the use of GnRH at the time of breeding also did not significantly improve the reproductive rate in goats.

Short-term results of magnetic resonance imaging-guided focused ultrasound surgery for patients with adenomyosis: symptomatic relief and pain reduction

The objective of this study was to evaluate the degree of symptomatic relief obtained after treatment with magnetic resonance-guided focused ultrasound surgery in patients with adenomyosis. Quality of life and pain assessment questionnaires from 35 women, collected on the day of treatment and up to 6 months after treatment, indicated that the treatment was safe and there was a significant reduction in symptoms.

The effect of a GnRH antagonist pre-treatment, in the superovulation of goats

The effect of a short pre-treatment with a GnRH antagonist (Cetrorelix acetate) and the induced superovulation response was evaluated in goats. A total of 16 nanny goats were allocated to two groups. The goats in the antagonist treatment group ( n = 8) received 6 doses of the GnRH antagonist, once daily, as a pre-treatment to superovulation. The does in the control group were provided with saline only. Natural mating was implemented using three fertile bucks. Large follicles on the ovaries were detected via ultrasound at 3.5 MHz. All goats were laparotomized and the CL's and cystic follicles visually recorded. Embryos were recovered via flushing and recorded 6 days after sponge removal. The number of large follicles induced and embryos produced were significantly increased by treatment. However, no differences were noted regarding the numbers of cystic follicles, indicating a lack of negative side-effects following the use of GnRH. In general, the number of large follicles and embryos were significantly ( P < 0.05) higher in the treated group. It was demonstrated that a GnRH antagonist treatment can improve the superovulatory response by 64% and embryo recovery rate by 90% in goats.

Progesterone, Follicular, and Estrual Responses to Progesterone-Based Estrus and Ovulation Synchronization Protocols at Five Stages of the Estrous Cycle

The objective was to monitor changes in ovarian status in heifers exposed to a progesterone insert with or without concurrent GnRH injection. Estrus was manipulated in 283 heifers (31 breeding clusters) by administering GnRH, progesterone, and PGF2α at 5 stages of the estrous cycle. Estrus was presynchronized with a progesterone insert (CIDR) for 7 d before PGF2α was administered 24h before insert removal. Successive clusters of heifers were assigned to treatments (2 heifers per treatment) on cycle d 2, 5, 10, 15, and 18. Treatments consisted of a progesterone insert (d 0) for 7 d plus: 1) PGF2α on d 6, 24h before insert removal (early PGF); 2) GnRH on d 0 + early PGF2α (GnRH + early PGF); 3) PGF2α at insert removal (late PGF); and 4) GnRH on d 0 + late PGF (GnRH + late PGF). Controls received GnRH on d 0 and PGF2α on d 7. Ovaries were scanned by transrectal ultrasonography on d 0, 2, 7, 9, and 11 to assess follicle diameters and ovulation. Blood was collected on d 0, 2, 6, 7, 8, and 9 to quantify serum concentrations of progesterone. Insemination occurred after detected estrus or by timed artificial insemination (TAI) at 64h after insert removal. Only 25% of 141 GnRH-treated heifers ovulated by d 2; twice as many ovulated when treatment was initiated on d 5 (46.4%) than on other cycle days (20.3%). Diameters of the largest follicle exposed to GnRH on d 0, 2, 7, or 9 did not differ regardless of whether ovulation occurred. Small treatment and stage of cycle differences in diameter of the largest follicle were detected on d 2, 7, and 9. Compared with controls, progesterone concentration was greater in all progesterone-treated heifers on d 2 and 6. Early- vs. late-PGF treatment resulted in less progesterone on d 7 and 8. Pregnancies per AI were less after TAI (44%) than after detected estrus (56%) and were less in controls than in all progesterone treatments. Heifers in which treatments were initiated on d 10 of the cycle had the most consistent (estrus vs. TAI) pregnancies per AI (65.4%) compared with other cycle days. Compared with controls, more progesterone-treated heifers ovulated by 96h after insert removal. Application of the progesterone insert reduced variance of the interval to estrus after insert removal (or PGF2α injection in controls) by 1.6-fold compared with controls. These results do not support the use of GnRH in a progesterone-based synchronization protocol.

The use of gonadotropin-releasing hormone analog in preservation of ovarian function in women undergoing chemotherapy: a systematic review and meta-analysis

ObjectiveTo evaluate the efficacy and safety of gonadotrophic-releasing hormone analog (GnRHa) co-treatment in preservation of ovarian function during gonadotoxic chemotherapy.DesignMeta-analysis.Materials and methodsA Medline, Embase, Scopus and Web of Science databases literature search from inception up to March 2007 was performed to identify published clinical trials and cohort studies comparing chemotherapy with GnRHa to chemotherapy alone in premenopaual women without restriction to language of publication. The methodological quality was evaluated using validated scales and the outcome-data was extracted. Agreement was evaluated using K statistics. Funnel blot was used for the assessment of publication bias. POF was considered the primary outcome. Secondary outcomes included; post-treatment pregnancy and treatment related complications. Random effect models were used to calculate the pooled relative risk (RR) for different outcomes. Subgroups were specified a priori and test for interaction was used for evaluation of difference in efficacy among subgroups.ResultsConclusionsCurrent evidence from observational studies suggests a beneficial value of the use of GnRH along with chemotherapy in premenopusal women. This hypothesis should be tested in the context of a well designed RCT with objective timely endpoints and including all indications and types of chemotherapy. ObjectiveTo evaluate the efficacy and safety of gonadotrophic-releasing hormone analog (GnRHa) co-treatment in preservation of ovarian function during gonadotoxic chemotherapy. To evaluate the efficacy and safety of gonadotrophic-releasing hormone analog (GnRHa) co-treatment in preservation of ovarian function during gonadotoxic chemotherapy. DesignMeta-analysis. Meta-analysis. Materials and methodsA Medline, Embase, Scopus and Web of Science databases literature search from inception up to March 2007 was performed to identify published clinical trials and cohort studies comparing chemotherapy with GnRHa to chemotherapy alone in premenopaual women without restriction to language of publication. The methodological quality was evaluated using validated scales and the outcome-data was extracted. Agreement was evaluated using K statistics. Funnel blot was used for the assessment of publication bias. POF was considered the primary outcome. Secondary outcomes included; post-treatment pregnancy and treatment related complications. Random effect models were used to calculate the pooled relative risk (RR) for different outcomes. Subgroups were specified a priori and test for interaction was used for evaluation of difference in efficacy among subgroups. A Medline, Embase, Scopus and Web of Science databases literature search from inception up to March 2007 was performed to identify published clinical trials and cohort studies comparing chemotherapy with GnRHa to chemotherapy alone in premenopaual women without restriction to language of publication. The methodological quality was evaluated using validated scales and the outcome-data was extracted. Agreement was evaluated using K statistics. Funnel blot was used for the assessment of publication bias. POF was considered the primary outcome. Secondary outcomes included; post-treatment pregnancy and treatment related complications. Random effect models were used to calculate the pooled relative risk (RR) for different outcomes. Subgroups were specified a priori and test for interaction was used for evaluation of difference in efficacy among subgroups. Results ConclusionsCurrent evidence from observational studies suggests a beneficial value of the use of GnRH along with chemotherapy in premenopusal women. This hypothesis should be tested in the context of a well designed RCT with objective timely endpoints and including all indications and types of chemotherapy. Current evidence from observational studies suggests a beneficial value of the use of GnRH along with chemotherapy in premenopusal women. This hypothesis should be tested in the context of a well designed RCT with objective timely endpoints and including all indications and types of chemotherapy.

Use of GnRH to induce an accessory corpus luteum in buffaloes fixed time artificially inseminated

The objective of this study was to induce an accessory corpus luteum (CL) in buffaloes fixed time artificially inseminated. Two hundred and forty buffaloes received the treatment sequence GnRH/PGF2α/GnRH after which were inseminated artificially. Six days after the insemination, the animals were divided in two groups (G1 = Control and G2 = GnRH) and received 0 µg or 25 µg of GnRH to induce an accessory CL. After twenty four days (D40), pregnancy diagnosis was performed by ultrasonography and 79 buffalo (G1, n = 39; G2, n = 40) were randomly selected to verify the ovary status by ultrasound. Fifty three pregnant buffaloes (G1, n = 32; G2, n = 21) were followed to verify the birth rate. Data were analyzed by Chi-square test. The conception rate, the accessory CL rate and the birth rate were higher in G2 than in G1 (P<0.05). The use of GnRH to induce an accessory CL in buffaloes increased the conception and birth rates. Thus, the increase of the cost of Ovsynch protocol with the thirty dose of GnRH is rewarded by the increment on conception and birth rates and reduction of days open.

Ovulation and conception rates according intravaginal progesterone device and hCG or GnRH to induce ovulation in buffalo during the off breeding season

The objective of this study was to evaluate the effect of intravaginal progesterone device (P4; first or second use) of different ovulatory inductors on ovulation and conception rates in buffaloes during the off breeding season. Two hundred and forty two buffaloes were allocated in four groups and received P4 device of first or second use plus estradiol benzoate on Day 0 (D0). The P4 device was removed and a dose of PGF2α and eCG was administered on D9. On D11, buffaloes received hCG or GnRH and 16hs after the animals were inseminated. The ultrasound examination was performed on D0 to verify the ovarian status, from D9 to D14 to establish the moment of ovulation and on D40 for pregnancy diagnosis. Data were analyzed by ANOVA and Chi-square test. There was no effect of interaction. The ovulation and conception rate were similar for P4 device of first and second use, for hCG and GnRH. Results indicate that the use of P4 device for two times and the use of GnRH instead of hCG provide satisfactory ovulation and conception rate in buffalo during the off breeding season and might reduce the cost of the protocol for artificial insemination.

Comparison of the Ovsynch Protocol and Exogenous Progesterone with Insemination at an Induced Estrus as Therapeutic Strategies for Ovarian Cysts in Lactating Dairy Cows

It has been suggested that an underlying mechanism in the development of bovine ovarian cysts involves a hypothalamic lesion which causes follicular estrogen to be ineffective in inducing a GnRH/LH surge at the time of estrus. This lesion involves the estrogen receptor alpha (ERa). Furthermore, it has been speculated that treatment with progesterone may induce the ERa in the mediobasal hypothalamus which will foster a GnRH/LH surge in response to follicular estrogen. Collectively, this information suggests that therapeutic strategies for bovine ovarian cysts could involve either the use of GnRH or exogenous progesterone. An intra vaginal progesterone insert (EAZI-BREED™ CIDR®) has been approved for use in lactating dairy cows. The use of a CIDR to synchronize estrus detection is relatively simple and less labor intensive than the OvSynch protocol. Therefore, it could be a more acceptable treatment for ovarian cysts in lactating dairy cows. However, there is no information available concerning the comparative efficacy of these two treatment strategies. The hypothesis of this study was that lactating dairy cows with ovarian cysts treated with exogenous progesterone, a luteolytic dose of PGF2a, and inseminated at an induced-estrus, will have a higher pregnancy rate compared to cows with ovarian cysts subjected to the OvSynch protocol. The purpose of this study was to compare the effectiveness of these two protocols.

Veterinary clinical application of GnRH—questions of efficacy

The efficacy of GnRH treatments are reviewed in relation to prevention of embryo mortality, control of follicle development in synchronization programmes using PG as luteolysin, induction of ovulation in post-partum anoestrus and in bovine cystic ovarian disease. It is suggested that in cattle that GnRH is effective in increasing pregnancy rates when given either at the time of insemination (first or repeat) or between days 11 and 14 after insemination. Evidence is also presented for positive effects on pregnancy rates in sheep, mares and sows. Use of GnRH as an integral part of synchronising regimens where it is given 7 days before PG and then again 48–60 h after PG appears to be effective in increasing the synchrony of ovulation in controlled breeding programmes. The main synchronizing effect seems to reside in the second GnRH injection whereas the importance of the first is in prolonging the luteal phase in those cows treated late in the cycle. The published work on the potential use of GnRH to induce ovulation in anovulatory cattle is reviewed. Neither bolus dose injections, pulsatile, continuous infusion, nor controlled release formulations of GnRH, have yet proved effective in inducing fertile ovulations in a predictable or consistent manner. It is suggested that this is due to the variability of follicular status when treatment is initiated. GnRH is commonly used in the treatment of bovine cystic ovarian disease. However, although stimulating ovulation/luteinisation of a new follicle and luteinisation of the cyst, fertility of treated cattle remains very poor and it is suggested that a better understanding of the disease is needed before more effective treatments can be developed.

Effects of GnRH Administered to Cows at the Onset of Estrus on Timing of Ovulation, Endocrine Responses, and Conception

Two experiments examined effects of GnRH administered within 3h after onset of estrus (OE) on ovulation and conception in dairy cows. In experiment 1, 46 cows received either saline, 250μg of GnRH, or 10μg of the GnRH analogue, Buserelin. Cows were observed for estrus, blood samples were collected, and ovulations were monitored by ultrasound. In controls, 76% of cows had intervals from estrus to ovulation of≤30h and 24% had intervals>30h. Treatment with either GnRH or GnRH analogue (data combined) increased magnitude of LH surges and decreased intervals from estrus to LH surge or to ovulation. Treated cows all ovulated≤30h after OE. Among control cows, plasma estradiol concentrations before estrus correlated positively with amplitudes of LH surges. Higher plasma progesterone was observed in the subsequent estrous cycle in GnRH-treated cows compared to control cows with delayed ovulations. Experiment 2 included 152 primiparous and 211 multiparous cows in summer and winter. Injection of GnRH analogue at OE increased conception rates (CR) from 41.3 to 55.5% across seasons. In summer, GnRH treatment increased CR from 35.1 to 51.6%. Across seasons, GnRH increased CR from 36.0 to 61.5% in cows with lower body condition at insemination and GnRH increased CR (63.2 vs. 42.2%) in primiparous cows compared to controls. Use of GnRH eliminated differences in CR for cows inseminated early or late relative to OE and increased CR in cows having postpartum reproductive disorders. In conclusion, GnRH at onset of estrus increased LH surges, prevented delayed ovulation, and may increase subsequent progesterone concentrations. Treatments with GnRH increased conception in primiparous cows, during summer, and in cows with lower body condition.

Effect of Dose of GnRH Used in the Ovsynch System on AI Pregnancy Rates in Beef Cows

Estrous synchronization advances have the potential to dramatically increase the utilization of artificial insemination (AI) in beef cattle operations. Ultimately, the level of usefulness of these programs and AI in general will be the cost effectiveness of programs which are developed. Programs involving the use of GnRH and prostaglandins have been reported that allow for acceptable pregnancy rates using timed insemination and thus dramatically reducing handling, a significant deterrent to AI in beef cattle. One such scheme, Ovsynch, has utilized 100mg of GnRH for each of two injections in the scheme. Research conducted with dairy cattle has suggested that 50 mg GnRH provides similar pregnancy rate outcomes. Beef cow reproduction is significantly different than dairy reproduction due to different body composition, lactational demands and typical nutritional provision. If a lower dose of GnRH produces similar pregnancy outcomes, a significant economic advantage to the program would result. This trial was designed to compare the outcome of the four different combinations of 50 mg and 100 mg of GnRH in Ovsynch protocols.

New biotechnological procedures in swine reproduction

New biotechnological procedures and the use of hormones in swine breeding are aimed at increasing the number of piglets in the litter. In small herds and groups, selected sows with 16 mammary complexes (tits) can yield up to 32 piglets, or porkers, per year per sow. In order to achieve such reproduction results, special, individual stalls for sow deliveries are used, in addition to biotechnological methods, with a warm core and floor heating, phased diet and clean facilities. The ovulation value in swine is determined by their genetic and paragenetic effects, and it is often provoked and increased with injections and preparations for superovulation. However, the results vary, since any administration of hormone injecions can reduce the reproductive cycle, shorten the duration of estrus, or disrupt the work of ovaries and create cystic follicles. The use of follicle-stimulating hormones in quantities up to 1000 IU per animal for the induction and synchronization of estrus has become customary for sows and gilts, as well as the use of prostaglandins, the use of GnRH for increasing ovulation in swine and increasing the number of follicles &gt;4 mm in diameter in the implementation of new biotechnologies in swine breeding, increases the number of ovulations and fertility in swine. In this way, reproduction is raised to the highest possible level, and artificial insemination of sows has 12 separate rules which enable better and more successful artificial insemination of sows.

The effects of gonadotrophin releasing hormone in prostaglandin F2α-based timed insemination programs for beef cattle

Trials were conducted in the spring (May; n = 324) and fall (October; n = 132) with crossbred continental-type beef cows assigned on the basis of parity and postpartum interval to one of three timed-AI treatments and one of two post-AI treatments. The timed-AI treatments were: (DPG) double (14 d apart) PGF2α (Lutalyse®) and AI (day = 0) 72 h after the second PGF2α (day –3); (OVS) Ovsynch® with the second GnRH (Factrel®) at 48 h and AI at 66 h; and (BRC) the same as OVS except that the second GnRH was given at the time of AI. Half of the cows within each treatment were given GnRH on day 14. Plasma progesterone concentrations were determined for the day of the first injection and on days –3, 0, 14, and 21. Timed-AI pregnancy was diagnosed by ultrasonography at day 42 and confirmed at calving. For DPG, OVS and BRC, PGF2α responder rates were 75.9, 51.4 and 71.3%, respectively, in spring (P &lt; 0.05) and 70.4, 70.4 and 59.1% in fall (P &gt; 0.05), and AI pregnancy rates were 28.7, 44.9 and 44.4% in spring (P&lt; 0.05) and 25.0, 40.9 and 43.2% in fall (P &gt; 0.05). Post-AI GnRH had no significant effect on pregnancy or conception rates or day 21 progesterone. The use of GnRH in the PGF2α based timed-AI program improved pregnancy rates and the BRC treatment was as effective as OVS. Neither postpartum interval nor initial progesterone concentration influenced (P &gt;0.05) the effect of GnRH on AI pregnancy rate, and GnRH had no effect (P &gt; 0.05) on twinning rate or gender ratio. Key words: Beef cows, estrous synchronization, pregnancy, timed-AI, progesterone

Post partum suboestrus in dairy cows : comparison of treatment with prostaglandin F2α or GnRH + prostaglandin F2α + GnRH

AbstractTwo studies (expt. 1, 185 cows in 1996/97; expt. 2, 168 cows in 1997/98) were conducted with Prim ‘Holstein dairy cows in the Mayenne region (France) to investigate suboestrus. Cows which had not been observed in oestrus since calving were allocated alternately to treatment groups between 60 and 90 days post partum. Expt. 1. Group 1: GnRH (Day 0, 100 μg im), PGF2α (Day 7, 25 mg im), GnRH (Day 9, 100 μg im) with artificial insemination (AI) Day 10. Group 2 : PGF2α (Day 0, 25 mg im), AI at oestrus or if oestrus not observed a second PGF2α injection was given (Day 13) with AI on Day 16 and Day 17. Expt. 2. Group 1 : GnRH (Day 0, 100 /μg im), PGF2α (Day 7, 25 mg im), GnRH (Day 9, 100 μg im) with AI at observed oestrus after Day 0 or at Day 10 if oestrus not observed. Group 2 : PGF2α (Day 0, 25 mg im), AI at oestrus, or if oestrus was not observed a second PGF2α injection was given (Day 13) and AI at observed oestrus. Progesterone was measured in serum at Day 0 and in milk at AI. Pregnancy diagnosis was performed by measuring bovine Pregnancy Specific Protein B (bPSPB) (Day 50 + 3) and confirmed by ultrasonography when the result was doubtful.In expt. 1, farmers observed 47/101 (46.9 %) of group 1 cows in oestrus, 33/91 on Day 10 and 10 before Day 10. The progesterone concentrations were compatible with oestrus in 69/86 (80%) of cows on Day 10. In group 2, 36/83 (43.4 %) of cows were inseminated after the first PGF2α injection. After the second PGF2 α, only 29/43 (67 %) of cows had a low progesterone concentration at AI. The pregnancy rates were 36.1% and 32.5 % for groups 1 and 2, respectively. In expt. 2, oestrus was observed in 31/93 (33.7 %) of group 1 cows. In group 2, 51/75 (66 %) of cows were inseminated after the first injection of PGF2α, 13/75 (17.3 %) after the second and 11/75 (14.7 %) were not seen in oestrus. Pregnancy rates were 53.7% and 53.3% in groups 1 and 2, respectively. In conclusion, it is recommended that suboestrus be treated with PGF2α followed by AI at observed oestrus when oestrus detection is good while, the use of GnRH + PGF2α + GnRH is recommended when oestrus detection is poor.

The use of GnRH or estradiol to facilitate fixed-time insemination in an MGA-based synchronization regimen in beef cattle

Two experiments were conducted to compare pregnancy rates when GnRH or estradiol were given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based estrus synchronization program. Crossbred beef cattle were fed melengestrol acetate (MGA, 0.5 mg per day) for 7 days (designated days 0–6, without regard to stage of the estrous cycle) and given cloprostenol (PGF; 500 μg intramuscular (im)) on day 7. In Experiment 1, lactating beef cows ( n=140) and pubertal heifers ( n=40) were randomly allocated to three groups to receive 100 μg gonadorelin (GnRH), 5 mg estradiol-17β and 100 mg progesterone (E+P) in canola oil or no treatment (control) on day 0. All cattle were observed for estrus every 12 h from 36 to 96 h after PGF. Cattle in the GnRH group that were detected in estrus 36 or 48 h after PGF were inseminated 12 h later; the remainder were given 100 μg GnRH im 72 h after PGF and concurrently inseminated. Cattle in the E+P group were randomly assigned to receive either 0.5 or 1.0 mg estradiol benzoate (EB) in 2 ml canola oil im 24 h after PGF and were inseminated 30 h later. Cattle in the control group were inseminated 12 h after the first detection of estrus; if not in estrus by 72 h after PGF, they were given 100 μg GnRH im and concurrently inseminated. In the absence of significant differences, all data for heifers and for cows were combined and the 0.5 and 1.0 mg EB groups were combined into a single estradiol group. Estrus rates were 57.6, 57.4 and 60.0% for the GnRH, E+P and control groups, respectively ( P=0.95). The mean (±S.D.) interval from PGF treatment to estrus was shorter ( P<0.001) and less variable ( P<0.001) in the E+P group (49.0±6.1 h) than in either the GnRH (64.2±15.9 h) or control (66.3±13.3 h) groups. Overall pregnancy rates were higher ( P<0.005) in the GnRH (57.6%) and E+P (55.7%) groups than in the control group (30.0%) as were pregnancy rates to fixed-time AI (47.5, 55.7 and 28.3%, respectively). In Experiment 2, 122 crossbred beef heifers were given either 100 μg GnRH or 2 mg EB and 50 mg progesterone in oil on day 0 and subsequently received either 100 μg GnRH 36 h after PGF and inseminated 14 h later or 1 mg EB im 24 h after PGF and inseminated 28 h later in a 2×2 factorial design. Pregnancy rates were not significantly different among groups (41.9, 32.2, 33.3 and 36.7% in GnRH/GnRH, GnRH/EB, EB/GnRH and EB/EB groups, respectively). In conclusion, GnRH or estradiol given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based synchronization regimen resulted in acceptable pregnancy rates to fixed-time insemination.

Use of GnRH to increase the precision of estrus and augment timed insemination in heifers treated with melengesterol acetate and PGF2 (2000)

Use of GnRH to increase the precision of estrus and augment timed insemination in heifers treated with melengesterol acetate and PGF2 (2000)

Current concepts in synchronization of estrus and ovulation of dairy cows

Estrus synchronization has become a routine reproductive management tool for dairy producers. Reproductive performance has decreased over the last 25 yr on dairy farms, and the lack of estrus detection or inaccurate detection are major reasons for increased numbers of days open for the average cow. Estrus synchronization methods that control both the function of the corpus luteum and the development of follicles with viable oocytes are critical to efficacy. This article reviews some of the synchronization methods used in dairy cattle, especially the recent protocols involving the use of GnRH. Conception and pregnancy rates from a series of studies using the Ovsynch protocol averaged 34.9 and 34.9%, respectively. Conception and pregnancy rates from breeding at detected estrus after PGF2α averaged 37.7 and 19.8%, respectively. Because pregnancy rates are typically below 40%, possible methods for early identification of open cows and resynchronization will be discussed.