Dose Of GnRH Research Articles

Effect of GnRH treatment on ovarian activity and reproductive performance of low-prolific Rahmani ewes

This study was designed to evaluate the effect of GnRH treatment during different times of the reproductive cycle on ovarian activity, progesterone (P4) concentration, and subsequent fertility of low-prolific, subtropical, Rahmani ewes during breeding season. Forty-five ewes were synchronized for estrus using a double injection of 0.5 mL of PGF2α agonist (125-μg cloprostenol), 11 days apart. Ewes showing estrus (Day 0) were treated with 1 mL of GnRH agonist (4-μg buserelin) on the day of estrus (GnRH0, n = 12) or 7 days post-mating (GnRH7, n = 10) or on both days (GnRH0+7, n = 11) or not (control, n = 12). Ovarian response to the treatment and diagnosis of pregnancy were ultrasonographically monitored. Also, serum P4 concentration was determined weekly throughout 28 days post-mating. Results showed that neither total number of follicles nor their populations were changed on Day 0 or 7 days post-mating by the GnRH treatment. GnRH treatment on Day 0 or Day 7 post-mating or both days did not enhance ovulation rate compared with the control. The mean numbers of accessory CL increased (P < 0.05) in the GnRH7 group than those in the control and GnRH0 groups, whereas it was intermediate in the GnRH0+7 group. The greatest (P < 0.05) overall mean of serum P4 concentration was for the GnRH7 and GnRH0+7 groups, followed by the GnRH0 and control groups. Serum P4 concentration increased (P < 0.05) on Day 14 post-mating and continued higher (P < 0.05) until Day 28 post-mating in the GnRH7 and GnRH0+7 groups compared with the control. Regardless of the time of GnRH administration, GnRH treatment reduced (P < 0.05) pregnancy loss from Day 40 post-mating to parturition and tended to enhance (P < 0.20) lambing rate compared with the control. In conclusion, a single dose of GnRH at the time of estrus or 7 days post-mating could be used as an effective protocol to decrease pregnancy loss from Day 40 after mating to parturition in low-prolific Rahmani ewes.

Experimental model of toxin-induced subclinical mastitis and its effect on disruption of follicular function in cows

This study establishes an experimental model for subclinical mastitis induced by Gram-positive (G+) exosecretions of Staphylococcus aureus origin or Gram-negative (G−) endotoxin of Escherichia coli origin to examine its effects on follicular growth and steroid concentrations in Holstein dairy cows. Cows were synchronized with the Ovsynch protocol followed by a series of follicular cycles that included GnRH and PGF2α doses administered every 8 days. Cows received small intramammary doses of either G+ (10 μg, n = 10) or G− (0.5 μg, n = 6) toxin, or saline (n = 6; uninfected control) every 48 hours for 20 days. Follicular fluids were aspirated from preovulatory follicles before (aspiration one: control), at the end of (aspiration two: immediate effect), and 16 days after the end of (aspiration three: carryover effect) toxin exposure. During the 3 weeks of subclinical mastitis induced by G+ or G−, no local inflammatory signs were detected in the mammary gland and no systemic symptoms were noted: body temperatures of the treated cows did not differ from controls; plasma cortisol and haptoglobin concentrations were not elevated and did not differ among groups. Somatic cell count was higher in the treated groups than in controls, and higher in the G− versus G+ group. For analysis of reproductive responses, cows were further classified as nonaffected or affected based on an more than 20% decline in follicular androstenedione concentration in aspiration two or three relative to the first, control aspiration. Most G− (5/6) and 40% of G+ (4/10) cows were defined as affected by induced mastitis. An immediate decrease in the number of medium-size follicles was recorded on Day 4 of the induced cycle, toward the end of the 20-day mastitis induction, in the affected G+ compared with uninfected control group (1.0 ± 0.5 vs. 3.0 ± 0.4 follicles; P < 0.05); the affected G− and nonaffected G+ subgroups exhibited a similar numerical decline in the number of follicles. A carryover (but not immediate) decrease to 51% and 62% in follicular estradiol concentrations in G− affected group and G+ affected group was detected relative to controls (P < 0.05). The nonaffected G+ subgroup did not differ from its control counterparts. Based on the current experimental model, subclinical IMI induced by G+ or G− toxin disrupts follicular functions, and it seems that the ovarian pool of early antral follicles is susceptible to subclinical mastitis.

Effect of delayed breeding during the summer on profitability of dairy cows

The objective of this retrospective observational cohort study, combined with simulation, was to evaluate the effect of extending the voluntary waiting period (VWP) during the summer on profitability on a Florida dairy farm. Data from Holstein cows (n=1,416) that calved between June and September of 2007 and 2008 were used. Cows that calved between June 1 and July 21 (regular group; REG; n=719) were artificially inseminated (AI) for the first time upon estrus detection (ED) after the second PGF2α of the Presynch protocol administered between 57 and 63d in milk (DIM), or underwent timed AI using the Ovsynch protocol (TAI) if not detected in estrus. Cows that calved between July 22 and September 18 (extended group; EXT; n=697) underwent AI for the first time after the first or second PGF2α starting November 14 or November 21 or underwent TAI if not detected in estrus. For second and subsequent AI, all cows underwent AI upon ED or enrolled on TAI after nonpregnancy diagnosis. Following these schemes, average VWP in the REG group and EXT group were 60 and 83d, respectively. Overall profitability for both experimental and subsequent parities were calculated by subtracting the costs existing of feeding costs ($0.30/kg lactating cow diet; $0.25/kg dry cow diet), breeding costs ($2.65/dose PGF2α; $2.40/dose GnRH; $0.25/injection administration; $10/semen straw; $5/AI; $3/pregnancy diagnosis), and other costs ($3/d) from the daily revenues with milk sales ($0.44/kg of milk), cow sales ($1.76/kg of live weight), and calf sales ($140/calf). A herd budget simulation was used to predict future cash flow after culling or end of subsequent parity until 6yr after the start of the study to account for all cash flow consequences of extended VWP. Cows in the EXT group had greater first-service pregnancy per AI (PAI1) but still had greater days open and calving interval. Delaying breeding did not affect total cash flow because the EXT group had greater combined profitability for the experimental parity and subsequent parity but lesser future cash flow. Delayed breeding during the summer increased PAI1 but did not improve overall reproductive efficiency and did not affect overall profitability.

Evaluation of gonadotropin-releasing hormone hydrogen chloride at 3 doses with prostaglandin F2α for fixed-time artificial insemination in dairy cows

The objectives of the current study were to evaluate the efficacy and field safety of GnRH HCl administered at 3 doses in fixed-time artificial insemination (FTAI) programs (Ovsynch) in dairy cows. A common protocol was conducted at 6 commercial dairies. Between 188 and 195 cows were enrolled at each site (total enrolled = 1,142). Cows had body condition scores ≥2 and ≤4, were between 32 to 140d in milk, and were clinically healthy. Within pen and enrollment day (enrollment cohort), cows were assigned randomly in blocks of 4 to each of 4 treatments: (1) 25mg of PGF2α on d 7 with FTAI 72±2h later (control); (2) 100μg of GnRH on d 0, d 7 a dose of 25mg of PGF2α, and the second administration of 100μg of GnRH (T100) administered either at 48±2h (d 9) after PGF2α with FTAI 24±2h later or 56±2h (d 9) after PGF2α and FTAI 17±2h later; (3) same as T100 with both injections of 150μg of GnRH (T150); and (4) same as T100 with both injections of 200μg of GnRH (T200). Three sites selected the first option and 3 sites selected the second option for the timing of the second injection of all doses of GnRH. Cows were observed daily for signs of estrus and adverse clinical signs. Cows not returning to estrus had pregnancy diagnosis between 42 and 65d following FTAI. Pregnancies per FTAI (P/FTAI) were analyzed as a binary variable (1 = pregnant, 0 = not pregnant) using a generalized linear mixed model with a binomial error distribution and a logit link function. The statistical model included fixed effects for treatment, random effects of site, site by treatment, enrollment cohort within site, and residual. Parity (first vs. second or greater) was included as a covariate. For demonstration of effectiveness, α=0.05 and a 2-tailed test were used. Fifty-two cows were removed from the study because of either deviation from the protocol, injury, illness, culling, or death. Among the remaining 1,090 cows, 33.9% were primiparous and 66.1% were multiparous. Back-transformed least squares means for P/FTAI were 17.1, 27.3, 29.1, and 32.2% for control, T100, T150 and T200, respectively. The P/FTAI for each GnRH dose differed from that of the control. No differences were detected in P/FTAI between GnRH doses. No treatment-related adverse events were observed. Mastitis was the most frequently observed adverse clinical sign, followed by lameness and pneumonia. This study documents the efficacy and safety of doses of 100 to 200μg of GnRH as the HCl salt when used in Ovsynch programs.

The use of the gonadotropin-releasing hormone analog deslorelin for short-term contraception in red pandas (Ailurus fulgens)

Red pandas (Ailurus fulgens) are threatened with extinction owing to habitat loss, exacerbated by their unique ecology and low fecundity. Regional breeding programs manage captive red panda populations. Recommendations not to breed may be made for various reasons, including genetic overrepresentation of certain individuals. No recommendations have been published on the use of contraception for red pandas. This article discusses the use of the GnRH analog deslorelin as a reversible method of contraception in both male and female pandas. The mean time from last contraception to conception was 3 years with a 4.6-mg deslorelin implant. The average dose of GnRH implant received was 1.09 mg/kg (range, 0.88–1.32). Males returned to breeding sooner than females. No reproductive side effects were noted with up to three consecutive annual GnRH implants.

Luteal function, largest follicle, and fertility in postpartum dairy cows treated with 14dCIDR-PGF2α versus 2xPGF2α-Ovsynch for timed AI

A method for timed artificial insemination (AI) that is used for beef cows, beef heifers, and dairy heifers employs progesterone-releasing inserts, such as the controlled internal drug release (CIDR; Zoetis, New York, NY, USA) that are left in place for 14 days. The 14-day CIDR treatment is a method of presynchronization that ensures that cattle are in the late luteal phase of the estrous cycle when PGF2α is administered before timed AI. The objective of this study was to test the effectiveness of the 14dCIDR-PGF2α program in postpartum dairy cows by comparing it with the traditional “Presynch-Ovsynch” (2xPGF2α-Ovsynch) program. The 14dCIDR-PGF2α cows (n = 132) were treated with a CIDR insert on Day 0 for 14 days. At 19 days after CIDR removal (Day 33), the cows were treated with a luteolytic dose of PGF2α, 56 hours later were treated with an ovulatory dose of GnRH (Day 35), and 16 hours later were inseminated. The 2xPGF2α-Ovsynch cows were treated with a luteolytic dose of PGF2α on Day 0 and again on Day 14. At 12 days after the second PGF2α treatment (Day 26), the cows were treated with GnRH. At 7 days after GnRH, the cows were treated with PGF2α (Day 33), then 56 hours later treated with GnRH (Day 35), and then 16 hours later were inseminated. There was no effect of treatment or treatment by parity interaction on pregnancies per AI (P/AI) when pregnancy diagnosis was performed on Day 32 (115/263; 43.7%) or Days 60 to 90 (99/263; 37.6%) after insemination. There was an effect of parity (P < 0.05) on P/AI because primiparous cows had lesser P/AI (35/98; 35.7%) than multiparous cows (80/165; 48.5%) on Day 32. Cows observed in estrus after the presynchronization step (within 5 days after CIDR removal or within 5 days after the second PGF2α treatment) had greater P/AI than those not observed in estrus (55/103; 53.4% vs. 60/160; 37.5%; observed vs. not observed; P < 0.01; d 32 pregnancy diagnosis). When progesterone data were examined in a subset of cows (n = 208), 55.3% of cows had a “prototypical” response to treatment (i.e., the cow had an estrous cycle that was synchronized by the presynchronization treatment and then the cow responded appropriately to the subsequent PGF2α and GnRH treatments before timed AI). Collectively, cows with a prototypical response to either treatment had 52.2% P/AI that was greater (P < 0.001) than the P/AI for cows that had a nonprototypical response (19%) (P/AI determined at 60–90 days of pregnancy). In conclusion, we did not detect a difference in P/AI when postpartum dairy cows were treated with 14dCIDR-PGF2α or 2xPGF2α-Ovsynch before timed AI. The primary limitation to the success of either program was the failure of the cow to respond appropriately to the sequence of treatments.

Does single dose GnRH agonist administration after oocyte pick-up in antagonist cycles improve endometrial receptivity and pregnancy rates?

Does single dose GnRH agonist administration after oocyte pick-up in antagonist cycles improve endometrial receptivity and pregnancy rates?

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

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

Acid–Base Parameters and Steroid Concentrations in Pre‐Ovulatory Follicles and Plasma of Lactating Dairy Cows with Spontaneous and Synchronized Oestrus or Follicular Cyst

The study aimed to compare the acid-base balance and steroid concentrations between follicular fluids (FF) of pre-ovulatory follicles derived from a spontaneous oestrus (SO), synchronized or induced oestrus (IO) and follicular cysts (CYS) and between FF and blood in dairy cows. Forty-two dairy cows were included in this study. The animals were allocated to three groups: SO (n=23); IO (n=11) using GnRH at day 0 and day 9 and PGF2 α at day 7; and animals with CYS (n=10). The follicular fluids (FF) were aspirated from the cyst/pre-ovulatory follicles (∅≥15mm) after SO and after second GnRH dose in IO by transvaginal ultrasound-guided ovum pick-up technique. Blood samples (BL) were collected in heparinized vacutainer tubes. The oxygen tension (pO2) in FF of IO was higher (p<0.05) than in SO and CYS groups. There were negative correlations (p<0.001, r=-0.89) between FF and blood pO2. The carbon dioxide tension (pCO2) and lactate level in FF of CYS group were higher (p<0.05) than in SO and IO groups. There were negative correlations (p<0.01, r=-0.73) between blood and FF pO2. Oestradiol-17β concentration in pre-ovulatory follicles and plasma of the SO group was higher (p<0.001) than in IO and CYS groups. Progesterone concentration in pre-ovulatory follicles and plasma of the SO and IO groups was lower (p<0.01) than in CYS group. Plasma androstenedione concentration in SO and IO groups was higher (p<0.05) than in CYS group. In conclusion, acid-base parameters, E2 and P4 levels in the follicular fluid of both IO and CYS groups were deviated greatly from the physiological level (disturbances of intrafollicular/intracystic environment), which may affect the quality of both the oocyte and the granulosa cells.

Experimental investigation of the immunocastration efficacy of a single dose GnRH vaccine in male rats

Experimental investigation of the immunocastration efficacy of a single dose GnRH vaccine in male rats

Using Double Dose of GnRH for Reducing Incidence of Cystic Ovaries in Cows

Cystic ovarian disease (COD) has been recognized as a one of most important problem in dairy farm, it is a managerial and financial problem.120 Holstein cows with average age between 3 to 5 years were used in this study to determine whether giving GnRH at 14th day and 21st day after parturition (using two different types of GnRH) has a role in decreasing incidence of cystic ovaries during days open, and is there is any effects of this program on fertility parameters, (the interval from calving to conception, number of service per conception, first service conception rate,). Also, we refered to the season of milking to see how it affects in the incidence of COD. The findings of this study suggest that using two dose of GnRH (Receptal or Cystorlin), at 14 and 21 days after parturition did not give a significant difference comparing with the costs of the programs in preventing COD except a moderate result by using Cystrolin especially with cow more than one season which decreased the incidence by 11%. COD may reach to 42% in herd especially the high yielding Holstein cow. No significant effect on fertility parameters positively or negatively by using GnRH in postpartum period.

A Five-Day Progesterone Plus eCG-Based Fixed-Time AI Protocol Improves Fertility Over Spontaneous Estrus in High-Producing Dairy Cows Under Heat Stress

This study compared the efficiency of a five-day or standard (nine-day) progesterone-based regimen combined with equine chorionic gonadotrophin (eCG) in a fixed-time AI (FTAI) protocol for dairy cows. The data examined were derived from 3577 inseminations conducted in three dairy herds. Animals with no estrus signs detected over 21 days were randomly assigned to a PRID-9 or PRID-5 group. Cows in each group received a progesterone intravaginal device (PRID) for 9 or 5 days, respectively, PGF2α and eCG on PRID removal, and GnRH 48 h later. Fixed-time AI was performed 12 h after the GnRH dose. Cows artificially inseminated following spontaneous estrus during the study period were considered as controls. Based on the odds ratio, the likelihoods of animals in PRID-9 in the warm (conception rate [CR] of 22.3%) and cool (32% CR) periods, and control animals in the warm period (26.6% CR) becoming pregnant were reduced (by factors of 0.6, 0.3 and 0.4, respectively) compared with the control animals in the cool period (CR of 43.7%). The risk of a twin pregnancy was higher (51.4%) for cystic PRID-9 cows (by a factor of 3.6) and lower (9.9%) for cyclic PRID-5 animals (by a factor of 0.4) compared with the PRID-9 cyclic cows. These findings indicate that the proposed protocol achieves similar results during the cool or warm season to those obtained when AI is conducted at spontaneous estrus during the cool season. In addition, PRID-5 reduced twin pregnancy compared with PRID-9.

Serum anti-Müllerian hormone and basal serum FSH as predictors of poor ovarian response in assisted conception cycles

The aim of the study was to correlate serum AMH and serum FSH levels with ovarian response to stimulation in IVF–ICSI cycles. This was a prospective observational study conducted in a private assisted conception unit. One hundred and two patients were selected on their first IVF cycle. Basal serum FSH and serum AMH were measured one month before the stimulation cycle. A fixed dose GnRH antagonist protocol was used in all cycles transferring a maximum of three day-3 cleavage stage embryos. We defined poor ovarian response as retrieval of fewer than four mature oocytes in cycles requiring ⩾ 3000 IU of gonadotropins for stimulation or cycle cancellation due to poor response. The correlation between different parameters was expressed as a Spearman’s correlation coefficient. The clinical value of AMH and FSH as predictors of poor ovarian response as well as predictors of pregnancy was evaluated by constructing relevant receiver operator characteristics curves (ROC curves). Of these 102 cycles, 28 fitted our definition of poor response while the remaining 74 cycles all produced an adequate response to stimulation. There was a statistically significant difference between the adequate responders group and poor responders group regarding their mean age (31.5 versus 39.6, p < 0.001), the mean value of AMH (2.84 ng/ml versus 0.9 ng/ml, p < 0.0001) as well as the mean value of basal FSH (7.6 IU/ml versus 9.7 IU/ml, p < 0.0001). Serum AMH level had a positive correlation while serum FSH had a negative correlation with the number of oocytes collected while only serum AMH had a significant positive correlation with the occurrence of pregnancy. ROC curve analysis of our results showed that serum AMH with an optimal cut-off value of 1.2 ng/ml is a reliable predictor of poor ovarian response with an area under the ROC curve of 90.4%. Serum basal FSH with an optimal cut-off value of 8.9 IU/ml was of lower value than AMH as a predictor of poor ovarian response with an area under the ROC curve of 81.9%. However, neither serum AMH nor basal serum FSH was found to able to reliably predict the occurrence of pregnancy with an area under the ROC curve of 59.4% and 58.6% respectively. Our results show that serum AMH level is more reliable than basal serum FSH as a predictor of poor ovarian response to stimulation with a cut-off value of 1.2 ng/ml shown to predict poor ovarian response with a sensitivity of 91.7%.

Evaluation of the 5-day versus a modified 7-day CIDR breeding program in dairy heifers

Dairy heifers were used to compared the effects of two timed AI + controlled internal drug release (CIDR) protocols (5-day vs. a modified 7-day) on: (1) luteal regression to initiate a new ovarian follicular wave; (2) ovarian response to the initial GnRH injection; and (3) pregnancy outcomes. Holstein heifers (N = 543) were assigned randomly to two treatments: (1) 25 mg PGF2α (im) and a CIDR insert on Day −7 followed by 100 μg of GnRH (GnRH-1) on Day −5 and 25 mg PGF2α (im) at CIDR insert removal (7-day [7D]) on Day 0; or (2) 100 μg GnRH (GnRH-1) and insertion of a CIDR on Day −5 and 25 mg PGF2α (im) at CIDR removal (5-day [5D]) on Day 0. Insemination with frozen-thawed conventional or gender-biased semen occurred after detected estrus from Days 0 to 2 or by appointment at 72 h after PGF2α when a second 100-μg dose of GnRH was given. Blood was collected on Days −7, −5, 0, and 3 to determine concentrations of progesterone and incidence of luteolysis. Ovaries were scanned on Days −5 and 0. Luteolysis in the 7D treatment by 48 h after the initial PGF2α was greater (P < 0.01) than what occurred spontaneously in the 5D treatment (36.2% vs. 19.7%, respectively). Incidence of ovulation after GnRH-1 on Day −5 was greater (P < 0.05) for 7D than for 5D heifers, but the proportion of heifers with an induced CL on Day 0 did not differ between treatments. Heifers inseminated after detected estrus (166/543, 30.6%) on Days 0, 1, and 2 had greater (P < 0.05) pregnancy per AI (P/AI) at 32 days post AI than after timed AI (38.2% vs. 28.3%) on Day 3. Pregnancy P/AI, however, was greater (P < 0.05) for 7D heifers inseminated at estrus (46.5%) than for 7D heifers receiving the timed AI (26.8%) and differed (P < 0.05) from all 5D heifers regardless of insemination time at estrus (30.5%) or at timed AI at 72 h (29.9%). At the Florida location in which conventional and sexed semen were used during two breeding clusters, P/AI using sexed semen (43.9%, N = 56) did not differ from that of conventional semen (21.2%, N = 50). Remaining replicates of sexed semen produced similar P/AI at the other two locations (sexed = 27.6%, N = 71; and sexed = 31.9%, N = 215). We concluded that the modified 7-day CO-Synch + CIDR program produced more P/AI in heifers inseminated at estrus than a standard 5-day CO-Synch + CIDR program, but when timed AI occurred at 72 h after PGF2α and CIDR insert removal, P/AI did not differ between programs.

Influence of GnRH antagonist treatment duration and dose in a oocyte donation program

Influence of GnRH antagonist treatment duration and dose in a oocyte donation program

Follicular fluid concentrations of IGF-I, IGF-II, IGFBP-3, VEGF, AMH, and inhibin-B in women undergoing controlled ovarian hyperstimulation using GnRH agonist or GnRH antagonist

To compare follicular fluid concentrations of IGF-I, IGF-II, IGFBP-3, inhibin-B, VEGF, and AMH in women undergoing controlled ovarian hyperstimulation with a long-luteal GnRH agonist protocol or multiple-dose GnRH antagonist protocol. A total of 80 cycles were included; long-luteal GnRH agonist group (n=40) and multiple dose GnRH antagonist group (n=40). All follicular fluid samples were obtained from mature follicles during oocyte retrieval. IGF-I and IGFBP-3 concentrations were measured by immunoradiometric assay. IGF-II, VEGF, AMH, and inhibin-B concentrations were measured by enzyme-linked immunosorbent assay. There were no significant differences in the concentrations of the studied follicular fluid markers, cycle parameters, and treatment outcomes between GnRH agonist and GnRH antagonist protocols. The long-luteal GnRH agonist protocol and multiple-dose GnRH antagonist protocol seem to have similar effects on the follicular microenvironment in women undergoing controlled ovarian hyperstimulation.

Stimulation of a pulse of LH and reduction in PRL concentration by a physiologic dose of GnRH before, during, and after luteolysis in heifers

A single physiologic dose (5.0μg) of GnRH was given to 9 heifers each day (Hour 0) beginning on Day 15 postovulation until regression of the corpus luteum. Blood samples were taken each day for Hours −3, −2, −1, 0, 0.25, 0.5, 0.75, 1, 1.25, 1.50, 1.75, 2, 3, 4, and 5. Based on daily progesterone concentrations, data were grouped into phases of before (n=4), during (n=8), and after (n=7) luteolysis. The number of LH pulses with a peak at pretreatment Hours −2 or −1 (0.35±0.12pulses/sampling session) was less (P<0.0001) than for a pulse peak at posttreatment Hours 1 or 2 (1.0±0.0pulses/session). The characteristics and effects of LH pulses on progesterone and estradiol were similar between natural (pretreatment) and primarily induced (posttreatment) LH pulses. The same dose of GnRH stimulated an LH pulse with greater (P<0.05) amplitude after luteolysis than during luteolysis. Concentrations of PRL and number and prominence of PRL pulses decreased (P<0.05) between Hours 0 and 2 within each of the phases of before, during, and after luteolysis. The hypothesis that a physiologic dose of GnRH increases the concentration of PRL was not supported; instead, GnRH reduced the concentration of PRL. Results supported the hypotheses that an appropriate dose of GnRH stimulates an LH pulse during luteolysis that is similar to a natural pulse in characteristics and in the effects on progesterone and estradiol.

Effect of progesterone on magnitude of the luteinizing hormone surge induced by two different doses of gonadotropin-releasing hormone in lactating dairy cows

Ovulation to the first GnRH injection of Ovsynch-type protocols is lower in cows with high progesterone (P4) concentrations compared with cows with low P4 concentrations, suggesting that P4 may suppress the release of LH from the anterior pituitary after GnRH treatment. The objectives of this study were to determine the effect of 1) circulating P4 concentrations at the time of GnRH treatment on GnRH-induced LH secretion in lactating dairy cows and 2) increasing the dose of GnRH from 100 to 200μg on LH secretion in a high- and low-P4 environment. A Double-Ovsynch (Pre-Ovsynch: GnRH, PGF2α 7d later, GnRH 3d later, and Breeding-Ovsynch 7d later: GnRH, PGF2α 7d later, and GnRH 48h later) synchronization protocol was used to create the high- and low-P4 environments. At the first GnRH injection of Breeding-Ovsynch (high P4), all cows with a corpus luteum ≥20mm were randomly assigned to receive 100 or 200μg of GnRH. At the second GnRH injection of Breeding-Ovsynch (low P4) cows were again randomized to receive 100 or 200μg of GnRH. Blood samples were collected every 15min from −15 to 180min after GnRH treatment, and then hourly until 6h after GnRH treatment. As expected, mean P4 concentrations were greater for cows in the high- than the low-P4 environment. For cows receiving 100μg of GnRH, the LH peak and area under the curve (AUC) were greater in the low- than in the high-P4 environment. Similarly, for cows receiving 200μg of GnRH, the LH peak and AUC were greater in the low- than the high-P4 environment. Cows receiving 100 or 200μg of GnRH had greater mean LH concentration in the low- than the high-P4 environment from 1 to 6h after GnRH treatment. On the other hand, when comparing the effect of the 2 GnRH doses in the high- and low-P4 environments, cows receiving 200μg of GnRH had a greater LH peak and AUC than cows treated with 100μg of GnRH both in the high- and low-P4 environments. For the high-P4 environment, mean LH was greater from 1.5 to 5h after GnRH treatment for cows receiving 200μg of GnRH than for those receiving 100μg of GnRH. In the low-P4 environment, mean LH was greater for cows receiving 200μg of GnRH than for those receiving 100μg of GnRH from 1 to 2.5h after GnRH treatment. We conclude that the P4 environment at GnRH treatment dramatically affects GnRH-induced LH secretion, and that a 200-μg dose of GnRH can increase LH secretion in either a high- or a low-P4 environment.

Comparative efficacy of different CIDR protocols for the treatment of postpartum anestrous in Iraqi buffaloes

The aim of this study was to evaluate and compare the efficacy of different CIDR protocols including some hormonal preparations for the treatment of postpartum anestrous of Iraqi northern buffaloes. The present study was conducted on 70 anestrous buffaloes suffering from postpartum ovarian inactivity. Buffaloes were randomly assigned to three treatment groups. Buffaloes in Treatment 1 (n=20) injected on day 0 of the experiment, GnRH 250 ig and a CIDR was placed in the anterior vagina. On day 7, they were injected with 25 mg of PGF2a and on the following day (day 8) the CIDR were removed. On day 9 a second dose of GnRH (250 ig) was injected. Buffaloes in Treatment 2 (n=20) received on day 0 GnRH (250 ig) and a CIDR were placed in the anterior vagina. On day 7, CIDR were removed and injected with GnRH (250 ig). Treatment 3 (n=20) on day 0 a CIDR were placed in the anterior vagina. On day 6, they were injected with 1000 IU of eCG. CIDR were removed on day 7 and injected with GnRH (250 ig). A control group (n=10) received no treatments. Results showed that in 8days treatment 1 (GnRH+CIDR— —7 PGF a+9 GnRH), 15 out of 20 buffaloes received treatment exhibited estrus 2 within 69.4 ± 8.4 h after CIDR removal. The estrus induction rate was 75%. Total number of buffaloes became 7 days pregnant was 4 (26.7%). In treatment 2 (GnRH+CIDR— —GnRH), 65% of the buffaloes received treatment exhibited estrus within 77.8 ± 5.6 h after CIDR removal. Total number of buffaloes became pregnant was 4 7 days (26.7%). In treatment 3 (CIDR— — 6 eCG+7 GnRH), 100% of the buffaloes received treatment exhibited estrus within 78.3 ± 11.8 h after CIDR removal. In conclusion, our results indicate that the addition of GnRH and eCG to a progesterone-based CIDR protocol substantially improves the estrus induction and pregnancy rates in postpartum anestrous buffaloes.

Does the addition of clomiphene citrate or letrazole to gonadotropin treatment enhance the oocyte yield in poor responders undergoing IVF?

To evaluate the effect of adjunctive letrazole or clomiphene in IVF stimulation protocols. A retrospective analysis of high dose GnRH antagonist IVF cycles (450-600 IU of gonadotropins) that have met poor responder criteria. Selected consecutive cycles in same patients differed solely in presence or absence of adjunctive clomiphene or letrazole. Supplementation with clomiphene citrate in poor responders showed significant improvements (p < 0.05) in estradiol levels (1506 vs. 1044 pg/ml), number of dominant follicles (5.6 vs. 3.9), oocytes retrieved (5.2 vs. 3.4) and number of transferred embryos (1.7 vs. 1.1). It significantly improved biochemical pregnancy rates (18.1% vs. 5.9%) while reducing cycle cancellations (11.7% vs. 32.6%). Letrozole supplementation showed similar effects. Both Clomiphene and Letrazole performed similarly and showed significant effects. However, despite increasing oocyte yield and embryo transfer rates, the overall clinical and live birth rate in this population remained low and showed no measurable increase.