Dose Of GnRH Research Articles

Effect of repeated low doses of GnRH on follicular development and ovulation in anovulatory dairy cows with follicle growth to emergence size.

The aim of the study was to evaluate the effect of repeated low doses of GnRH agonist buserelin once a day for 5 days on follicle development and ovulation in anovulatory dairy cows with follicles growth only to emergence. The study was conducted on 71 anovulatory Polish Holstein Friesian cows. Anovulation with growth of follicles to emergence was defined as small ovaries with follicles of ≤ 5 mm in diameter and without corpus luteum on two examinations in a 7-10 day interval between 50-60 days after parturition. Cows were allocated to one of two group. Cows from group 1 (n = 58) received 0.4 μg of buserelin (Receptal, MSD, Poland) i.m. once a day for 5 days. Control cows from group 2 (n = 13) received saline. Ovarian structures were monitored weekly after the end of treatment by ultrasound for 4 weeks. The diameter of ovarian follicles on the ovaries was measured and recorded. Occurrence of ovulation was determined by the presence of corpus luteum. Overall, ovulation occurred in 46.6% (27/58) of cows treated with repeated doses of GnRH, while no corpus luteum was observed in the control group during the study period. There were significantly (p⟨0.05) more follicles 6-9 mm in diameter and 10-20 mm in diameter in cows treated with GnRH than in control cows. In conclusion, repeated low doses of GnRH analogue buserelin once a day for 5 days stimulate the development of ovarian follicles in anovulatory dairy cows with small ovarian follicles and led to ovulation in 46.6% of cows during 4 weeks after the end of the treatment.

Effect of PGF2α and GnRH administration on reproductive performance in Ghezel ewes

The main aim of the current study was to evaluate the effect of GnRH administration on day five after mating as well as PGF2α injection at the time of CIDR removal on the reproductive performance of Ghezel ewes. Estrus synchronization was performed using an intravaginal application of CIDR for 14 days and injection of 500 IU of PMSG at the time of CIDR removal. A total of 114 healthy fat-tailed ewes were randomly allotted into three groups as follow: control group (n = 35), did not receive any additional treatment; PG group (n = 44), each ewe received a dose of PGF2α at the time of CIDR removal; and PG+GnRH group (n = 35), the ewes received a dose of PGF2α at the time of CIDR removal and a single dose of GnRH, five days post-mating (post-conceptional day (PCD)− 5). Body condition score (BCS) of total ewes was determined at the time of CIDR insert. Blood samples were collected on PCD-19 for determining the serum progesterone levels. All the ewes were examined by transrectal ultrasonography 30–35 days after mating for pregnancy diagnosis. The serum values for P4 concentration were in control, PG and PG+GnRH groups 6.34 ± 1.17, 9.19 ± 2.55 and 10.57 ± 2.0 ng/mL respectively. The PG+GnRH treatment significantly increased the litter size compared to the control group (P = 0.04), but there were no significant differences in another reproductive indices between experimental groups. The multiple birth, twin, fecundity rates and litter size (P = 0.05, p = 0.03 and p = 0.003 respectively) were significantly higher in ewes with BCS > 2 compared to ewes with BCS ≤ 2. It is concluded that GnRH on PCD-5 treatment in addition to PGF2α injection at the time of CIDR removal could improve reproductive performance of Qezel ewes during non-breeding season.

Assisted reproduction of Clarias gariepinus Burchell, 1822

The objective of this work was to set up an experimental protocol concerning artificial reproduction in the catfish Clarias gariepinus with the induction of spawning using GnRH. The experiment was carried out at an aquaculture farm in Khemis Meliana (Ain Defla), Algeria. In the study, five African catfish broodstock (3 females and 2 males) were used. Hormonal injection was made into the back muscle below the fin, and doses of GnRH were determined according to the weight of each individual. Fertilisation was performed artificially using the dry method. After incubating the eggs, a binocular magnifying glass was used to check egg condition and embryonic development over time. The results obtained show that artificial insemination of this species, and survival and growth of larvae, are possible. After injection with GnRH, C. gariepinus females displayed successful ovulation, fertilisation, larval hatching, and larval monitoring. For this species, a latency period of 22 hours was recorded, and approximately 35,700 larvae were obtained. The fertilization rate was 48%. At the end of this experiment, we can conclude that it is possible to improve reproduction through the proper use of hormonal stimulation techniques and by improving the diet and abiotic factors that are dominant in fish farming.

Research Article: The effect of different doses of GnRH on stress responses in female koi carp (Cyprinus carpio)

Research Article: The effect of different doses of GnRH on stress responses in female koi carp (Cyprinus carpio)

PSVII-26 Follicular growth in beef cows when using a low dose of FSH and hCG at the time of CIDR removal in a 7-day co-synch + CIDR protocol

Abstract The aim of the study was to compare the growth of the periovulatory follicle in crossbreed cows receiving either a low dose of hCG (150 IU; Chorulon®, Merck) or a low dose of FSH (20 mg)Folltropin®, Vetoquinol) vs. a control group when applied at CIDR removal during an estrus synchronization protocol. At d0, a CIDR (Eazi-Breed CIDR®, Zoetis) was placed, a dose of GnRH (Factrel®, Zoetis) was applied i.m. and transrectal ultrasound was conducted to evaluate cyclicity status. On d7, cows (n = 79) were randomly assigned to three treatments (Control n = 27, FSH n = 26, and hCG n = 26) according to body condition score (1 to 9 scale) and cyclicity status. On the same day, CIDR was removed, a dose of prostaglandin analog (Lutalyse HighCon Injection®, Zoetis) was administered i.m. and an Estrotect™ patch was placed between the hip and tail head. Transrectal ultrasound was conducted to evaluate the diameter of the preovulatory follicle (DPF) at d7 and every 12h from d8 until ovulation was detected. Five cows that did not ovulate were removed from the study. Data were analyzed using GLIMMIX and LIFETEST procedures (SAS). The diameter at ovulation was not different among treatments (Control: 13.02 ± 0.53 mm; FSH: 12.38 ± 0.54 mm; hCG; 11.69 ± 0.47 mm; P = >0.10). Also, the time to ovulation was not different among treatments (P = 0.65; Figure 1a). However, cows of the control group presented estrus signs earlier than FSH and hCG groups (P = 0.02, Figure 1b). In conclusion, the use of a low dose of hCG or FSH at the time of CIDR removal did not increase the DPF or the time to ovulation.

Effect of Administration of Single Dose GnRH Agonist in Luteal Phase on Implantation Rate of Fresh ICSI Cycles

The luteal phase (LP) in the fresh ICSI cycle is insufficient, adequate LP support is one of the approved treatments for improving implantation and pregnancy rates. It is generally known that the LP is inadequate after ovarian stimulation due to negative from supra-physiological blood levels of steroids released by numerous corporal luteal, LH concentrations are low during the luteal phase. In this study, patients were divided into two groups: (40) patients as study group; those who received GnRHa (Decapeptil 0.1 mg), three days after embryo transfer, in addition to conventional luteal phase support (LPS) in the LP to increase the implantation and pregnancy rate in IVF; and their control group (40) received standard LPS only. On the second day of stimulation, blood samples for FSH, LH, TSH, E2, and prolactin were taken. On the day of ovulation induction, measure E2, progesterone, and LH; and on the day of embryo transfers, measure progesterone and LH. The overall characteristics of the patients in both groups were not significantly different. There was also no significant change in the number of total oocytes, mean of metaphase II oocytes percent, cleavage rate, grade I embryo percent, or serum hormones level between the study and control groups (p > 0.05). GnRH agonist treatment in the luteal phase improves clinical pregnancy and implantation rate in fresh ICSI cycles but is not statistically significant.

Effect of Administration of Single Dose GnRH Agonist in Luteal Phase on Implantation Rate of Fresh ICSI Cycles

The luteal phase (LP) in the fresh ICSI cycle is insufficient, adequate LP support is one of the approved treatments for improving implantation and pregnancy rates. It is generally known that the LP is inadequate after ovarian stimulation due to negative from supra-physiological blood levels of steroids released by numerous corporal luteal, LH concentrations are low during the luteal phase. In this study, patients were divided into two groups: (40) patients as study group; those who received GnRHa (Decapeptil 0.1 mg), three days after embryo transfer, in addition to conventional luteal phase support (LPS) in the LP to increase the implantation and pregnancy rate in IVF; and their control group (40) received standard LPS only. On the second day of stimulation, blood samples for FSH, LH, TSH, E2, and prolactin were taken. On the day of ovulation induction, measure E2, progesterone, and LH; and on the day of embryo transfers, measure progesterone and LH. The overall characteristics of the patients in both groups were not significantly different. There was also no significant change in the number of total oocytes, mean of metaphase II oocytes percent, cleavage rate, grade I embryo percent, or serum hormones level between the study and control groups (p > 0.05). GnRH agonist treatment in the luteal phase improves clinical pregnancy and implantation rate in fresh ICSI cycles but is not statistically significant.

P–685 Luteinization after final oocyte maturation induction is not compromised in women that receive double dose of Gonadotrophin-releasing hormone antagonists during controlled ovarian hyperstimulation

Abstract Study question Does the use of double dose of GnRH antagonists during COH in women with risk of premature LH surge alter luteinization after final oocyte maturation induction? Summary answer The use of double dose of GnRH antagonist in women with risk of premature luteinizing hormone surge dosent affect luteinization after final oocyte maturation induction. What is known already GnRH antagonists are used to prevent a premature LH surge during controlled ovarian hyperstimulation. The antagonists directly inhibit gonadotrophin release within several hours through competitive binding to pituitary GnRH receptors, producing a rapid suppression of LH and FSH, with no initial flare effect. In women with diminished ovarian reserve (DOR) it is not uncommon that premature luteinization cannot be completely prevented using a daily dose GnRH antagonist. To date, no study has evaluated the effects of using a daily double dose of GnRH antagonists to prevent a premature LH surge and its effect on luteinization after final oocyte maturation induction. Study design, size, duration This monocentric retrospective analysis evaluated the effect on luteinization after final oocyte maturation induction in twenty women during COH who received a daily double dose of GnRH antagonists (Cetrotide 0.25 mg/mL, Merck) from January 2020 to December 2020. Participants/materials, setting, methods Women with severe DOR and history of premature luteinization during COH received a double dose of GnRH antagonist when the leading follicle reached 12–14 mm (am and pm). When two follicles reached ≥18 mm in diameter, final oocyte maturation was induced with dual trigger using Leuprolide acetate and hCG. Progesterone, estradiol, bHCG, and LH levels were measured the day after final oocyte maturation induction to assure adequate luteinization. Main results and the role of chance In total twenty women were included in the analysis. Mean age 36.8± 4.2, AMH 0.65± 0.32 ng/ml, baseline antral follicle count 4± 2.3, serum hormone levels the day of ovulation induction trigger: progesterone 0.89± 0.34 ng/ml, LH 1.6± 2.1 ng/ml, estradiol 1235 ± 1420 pg/ml. Post-surge serum hormone levels average reached adequate levels: estradiol 1645 ± 1116 pg/ml, progesterone 20.4 ±2.2 ng/ml, LH 62.66± 10.5 IU/ml and, bHCG 247±115 IU/ml. A total of 76 oocytes were retrieved (3.8± 0.8 oocytes per patient), 63.1% (48/76) MII, 22% (17/76) MI, 14% (11/76) GV. Limitations, reasons for caution The retrospective nature of the study, small sample size, and potential variability in the study center’s laboratory protocol(s) compared to other reproductive treatment centers may limit the external validity of our findings. Wider implications of the findings: The daily use of double dose of GnRH antagonists during COH offers the possibility of preventing a premature LH surge in women with DOR with high risk of early ovulation, without compromising luteinization after final oocyte maturation induction. Trial registration number NA

Hypothalamic involvement and the role of progesterone in the NGF-induced LH surge pathway.

To elucidate the mechanism by which nerve growth factor (NGF) influences the LH secretory pathway in camelids, a series of experiments were done to determine the involvement of the hypothalamus (Experiment 1), the role of GnRH neurons (Experiment 2), and the effect of progesterone (Experiment 3) on the NGF-induced LH surge and ovulation in llamas. In Experiment 1, the declining phase of the NGF-induced LH surge was used to determine if the decline is a result of pituitary depletion or hypothalamic unresponsiveness. Female llamas were treated with NGF and, 7 h later, assigned to three groups and given a second dose of NGF (n = 5), a dose of GnRH (n = 5), or saline (n = 6). The LH response was attenuated after the second dose of NGF vs GnRH. In Experiment 2, Fos expression (marker of neuronal activation) in GnRH neurons was examined in the hypothalamus of llamas after NGF or saline treatment (n = 3 per group). Despite an LH surge in the NGF group but not in the saline group, no differences were detected between groups in Fos/GnRH co-expression. In Experiment 3, llamas in low-, medium-, and high-plasma progesterone groups (n = 4 per group) were treated with NGF. The NGF-induced LH surge did not differ among treatment groups. Results from the present study show that the induction of a preovulatory LH surge by NGF may be controlled by a novel pathway involving GnRH neuro-terminals downstream of the hypothalamus and is independent of progesterone influence.

Fixed timed artificial insemination and early resynchronization of ovulation in different categories of ewes in grazing system: Response of multiparous, nulliparous, and lactating ewes during the breeding season

The aims of this study were to: 1) determine if the insertion of a second MAP sponge in ewes 12 days after the first FTAI affects the pregnancy rate; 2) compare the responses to resynchronization protocol in multiparous and nulliparous ewes; and 3) compare the responses to resynchronization protocol in multiparous and postpartum lactating ewes. Three trials were performed with 186 Corriedale ewes: 111 multiparous [(control – CON (n = 60) and synchronization – SYNC groups (n = 51)], forty-two 1.5 yr-old nulliparous (group NUL), and 33 lactating ewes with at least 28 postpartum (group PtP). All ewes were treated with a MAP sponge for 6 days. Twenty-four hours before the sponge withdrawal, all animals received 0.24 mg of cloprostenol sodium and 300 IU of eCG, and 0.05 mg of gonadorelin 36 h after sponge withdrawal and artificially inseminated (AI) 27-30 h after the GnRH administration (Day 0). A second intravaginal sponge was inserted to all groups (except for SYNC group), on Day 12. On Day 17, early pregnancy diagnosis was performed with doppler ultrasound in all ewes. Sponge withdrawal occurred on Day 18, and a new GnRH dose (0.05 mg) was administrated 36 h after it. Once again, AI 27-30 h after the GnRH administration. A final pregnancy diagnosis on Day 42 was performed in all ewes for confirmation of first diagnosis and the data were confirmed by parturition. Ewes in all groups presented estrus signs (SYNCH – 94.1%; CON – 71.7%; NUL – 83.3%; PtP – 39.4% at first AI and CON – 65.2%; NUL – 76.5%; PtP – 62.5% at the second). Pregnancy rate and pregnancy loss were not different between synchronized and resynchronized multiparous ewes (SYNCH – 56.9% vs. CON – 58.3% pregnant at D42 and SYNCH – 5.9% vs. CON – 7.1% fetal loss at D42). No differences were found between resynchronized multiparous and nulliparous ewes at the first FTAI, only fecundity was higher in multiparous ewes [CON – 0.88 vs. NUL – 0.62 (P = 0.04)]. Resynchronized multiparous ewes had higher reproductive performance than postpartum ewes that only presented pregnancy after the second FTAI [CON – 73.3% vs. PtP – 15.1% total pregnancy (P = 0.003)]. Overall, synchronization-resynchronization FTAI treatments may be included in reproductive programs in nulliparous ewes, but the treatments cannot superimpose to the limiting conditions imposed by postpartum lactating status. The resynchronization treatments allow to include practical managements with no deleterious effects in the results of the first FTAI.

The Effect of GnRH on Reproductive Performance and Progesterone Hormone Levels in Buffalo in West Sumatera

The administration of hormone GnRH will affect the reproductive organs and can improve the reproductive performance of buffalo. The decrease of the buffalo population is caused by various factors including genetic and environmental factors. The development of buffaloes is relatively slow because the reproduction rate of buffaloes is lower than that of cattle, besides that it is also difficult to detect estrus, the pregnancy period is relatively long and longer calving rate. This study aims to determine the best dose of GnRH on the swamp buffalo producing of dadih in Indonesia. The materials used were 16 swamp buffalo. A completely randomized design was used in this study. Buffalo is synchronized with the injection of 5 ml of GnRH hormone n on the first and 11th day, on the 10th to 12th day all donor buffaloes are injected with GnRH. Four different doses of GnRH (200, 225, 250 and 275 ml/buffalo) and each treatment was replicated five times. The speed of estrus and estrus length were the measured variables. The results showed that the doses of GnRH significantly (P<0.05) increase of estrus speed and estrus length. Progesterone levels have increased significantly starting from before treatment until after treatment with GnRH. It is concluded that the best GnRH doses for estrus synchronization in the swamp buffalo producing of dadih was 2. 25 ml/buffalo with estrus speed 18.2 h and estrus length 18 h.

Different Timing of Adjuvant Low Dose hCG and GnRH Agonist Trigger Protocol, in OHSS High-Risk Patient with Peak E2 Level <4000 pg/mL

OBJECTIVE: The aim of the study is to compare the live birth rates between 1,500 I.U. of Human chorionic gonadotropin at the time of Gonadotropin-releasing hormone agonist trigger day or 35-36 h later on the oocyte pick-up day, without affecting the risk of significant ovarian hyperstimulation syndrome development in high-risk patients with peak E2 level <4,000 pg/mL STUDY DESIGN: This single-center prospective cohort study encompassed the period from March 2016 to March 2018 year. A total of 216 patients entered for final analysis, underwent a flexible antagonist protocol, intracytoplasmic sperm injection, and embryo transfer on the 3rd or 5th day in autologous cycles. Patients were randomized in one of two groups: Group A- Dual trigger group - 1,500 IU of Human chorionic gonadotropin at the time of Gonadotropin-releasing hormone agonist trigger day and Group B- 1,500 IU of Human chorionic gonadotropin 35-36 h later, on the oocyte pick-up day. To compare the two groups, we used nonparametric and parametric statistical tests. Significant differences were considered all values of p<0.05. RESULTS: There is no significant difference between the two (A vs B) groups according to the average number of retrieved oocytes (13.08 vs 14.41 p=0.08), M II oocytes (10.5 vs 10.95 p=0.46), GV (1.24 vs 1.52 p=0.09, the fertility rate (68.46% vs 64.04% p=0.07). The dual trigger group (A) had a significantly higher live birth rate (62.29% vs 42.37% p<0.05) compared with the Gonadotropin-releasing hormone-a trigger group (B). There were no cases of moderate or severe ovarian hyperstimulation syndrome in both groups. CONCLUSION: Our study shows that in hyper responders where the E2 peak is <4,000 pg/mL, the two approaches to the final oocyte maturation trigger have a correct outcome of the results, both in terms of the results from the in vitro fertilization and the low risk of ovarian hyperstimulation syndrome appearance.

Ratlarda Tekrarlayan Dozlarda GnRH uygulamasının, Östrojen α ve Progesteron B Reseptörlerine Etkisinin İmmunohistokimyasal Olarak Araştırılması

Sunulan bu çalışma da, tekrarlayan dozlarda GnRH enjeksiyonunun östrojen ve progesteron reseptörlerinin dağılımına etkisinin belirlenmesi amaçlandı. Çalışmada (n=24) adet rat kullanıldı. Gruplar; hiçbir uygulama yapılmayıp placebo enjeksiyonu yapılan kontrol grubu (n=6), tek GnRH enjeksiyonu yapılan Grup 1 (n=6), 5 gün üst üste GnRH enjeksiyonu yapılan Grup 2 (n=6), 10 gün süreyle tekrarlayan dozlarda GnRH uygulanan Grup 3 (n=6) olarak rastgele 4 gruba ayrıldı. Uygulama sonunda sakrifiye edilen ratlardan ovaryum ve uteruslar alınarak histolojik doku takip prosedürü ardından bloklandı. Kesilen dokular immunohistokimyasal olarak östrojen, progesteron reseptörlerinin dağılımı ve boyanma şiddeti yönünden incelendi. Tek doz GnRH uygulanan 1 grubunda ratlarda ovaryum ve uterusta kontrol grubuna benzer şekilde immunohistokimyasal reaksiyonlar şekillendi. 5 ve 10 gün süreyle GnRH uygulanan gruplarda ise uterusta ve ovaryumda immunohistokimyasal reaksiyonlar değişiklikler gösterdi. Kontrol ve 1 grupta ovaryumlar değerlendirildiğinde; Östrojen α reseptörlerinin, foliküllerdeki granüloza hücrelerinde, primer, sekunder ve graaf folikül duvarında granüloza hücrelerinde (+) olarak görüldü. Germinatif epitelde, damar duvarı endotel hücreleri, düz kas hücrelerinde ve interstisyel hücrelerde (+) reaksiyonlar tespit edildi. Kornu ve korpus uteri bölümlerinden alınan doku örneklerinde ise endometriyum epitelinde (+) reaksiyonlar görüldü. Grup 2 ve 3’te, ovaryum da benzer yerleşim bölgelerinde fakat boyanma şiddeti yönünden farklı şiddette reaksiyonlar tespit edildi. Progesteron B reseptörlerinin; Grup 1,2,3 ve 4’te korpus luteum luteal hücreleri, germinatif epitel, teka interna / eksterna hücreleri pozitif reaksiyon gösterdiği, gruplar arasında boyanma şiddetinin değiştiği görüldü. Kornu ve korpus uteride endometriyum epiteli, stratum bazalis bölgesi, miyometriyum ve perimetriyumda (+) reaksiyonlar tespit edilirken kontrol grubu örneklerinde miyometriyum bölgesinde (+) reaksiyon tespit edilemedi.

The effect of prostaglandin and gonadotrophins (GnRH and hCG) injection combined with the ram effect on progesterone concentrations and reproductive performance of Karakul ewes during the non-breeding season.

The effect of prostaglandin and gonadotrophins (GnRH and hCG) combined with the ram effect on the progesterone (P4) concentrations and reproductive performance of Karakul ewes was investigated during non‐breeding season. Ewes (n = 93) received a male effect and were divided into two treatment groups including GnRH ‐ hCG (hCG, n = 32), GnRH ‐ GnRH (GnRH, n = 30) and a control (n = 31) group. This study was carried out from April (hormonal injection) to October (lambing). The first doses of GnRH (4.2 μg, Buserelin) were injected at the beginning of the study in treatment groups. These ewes were treated with hCG (250 IU) or the second GnRH dose five days later. All animals received two injections (ten days apart) of 150 μg PGF2α five days after the hCG or the second GnRH injection. Mating was initiated two days after the second prostaglandin injection and lasted for 34 days. Blood samples were collected by jugular venipuncture on days −10, −5, 0 (first PGF2α injection), 17 and 30 during the study. Pregnancy diagnosis was performed through transabdominal ultrasonography on day 40 after the removing of ram. Conception rate was 93.8, 90 and 87.1% in the hCG, GnRH and control groups, respectively. Lambing rate tended to increase in the hCG group compared with the control group (87.1 versus 58.1%; p < .1). There was no significant difference in P4 concentrations among studied groups in identical sampling times (p > .05). In conclusion, the administration of prostaglandin and hCG in combination with the ram effect tended to decrease lambing period. In other words this protocol tended to increase lambing rate at the first cycle. Treatment with hCG or GnRH did not increase serum P4 concentrations of treated Karakul ewes during the non‐breeding season.

PULSATILE GONADOTROPIN RELEASING HORMONE (GNRH) VIA SUBCUTANEOUS PUMP FOR THE TREATMENT OF PRIMARY AMENORRHEA ASSOCIATED WITH HYPOGONADOTROPIC HYPOGONADISM

To compare the ovulation rate in women with primary amenorrhea, hypogonadotropic hypogonadism (HH) randomized to three GnRH doses (10, 15, 20 μg per pulse) delivered subcutaneous every 90 minutes with the LutrePulse OmniPod Pump versus a placebo control.

OR32-04 Dynamic Interactions Between Luteinizing Hormone and Testosterone in Healthy Community-Dwelling Men: Impact by Age and Body Composition

Context. Aging is associated with diminished testosterone (Te) secretion, which could be attributed to Leydig cell dysfunction, decreased pituitary stimulation and altered Te feedback. Objective. The goal was to quantify all three regulatory nodes of the GnRH-LH-Leydig cell- axis in the same cohort of healthy men, by measuring (1) indirectly the strength of the endogenous GnRH signal on the gonadotrope, (2) the strength of Te feedback on LH by ketoconazole (KTCZ), and (3) the effect of LH infusions on Te secretion, in relation to age and body composition. Design. This was a placebo-controlled, blinded, prospectively randomized cross-over study in 40 men, age 19–73 yr, BMI 20–34.3 kg/m2. A submaximal dose of ganirelix (GnRH antagonist) was used to assess outflow of GnRH, by calculating the difference between LH output during the control and ganirelix arm. Ketoconazole (steroidogenic inhibitor) was used to estimate feedback, by the difference in LH output during ketoconazole and control arm. High-dose ganirelix and repeated 6-min LH (18.75 IU) infusions were used to measure testicular responsivity. Blood sampling was at 10-min intervals. The 4 sessions were concluded with, a single submaximally GnRH stimulus to assess the responsiveness of the gonadotrope during ganirelix inhibition. Setting. The study was performed in a Clinical Translational Research Unit. Interventions. In 3 of the 4 experiments subjects underwent 5 h of blood sampling at 10-min intervals, starting at 0800 h. At 1100 h GnRH was injected and sampling was continued for another 2 h. Admission was at 1700 h the day before. At 2000 h they received KTCZ, dexamethasone or ganirelix and/or placebo. KTCZ and dexamethasone (or placebo) were administered again at 0700 when the IV catheter was placed. High-dose ganirelix was used to test the testicular responsiveness, and 7 LH pulses (90 min intervals) were given., with blood sampling from 1500 till 1300 h next day. Outcome measures. Mean concentrations of LH and (bio)Te, deconvolution analysis, endogenous dose-response LH-bioTe relation, and approximate entropy. Abdominal visceral fat (AVF) was calculated from single slice CT. Results. There were age-, but not body composition-related decreases in estimated endogenous GnRH secretion, Te’s feedback strength on LH, and Leydig cell responsivity to LH, accompanied by changes in approximate entropy. Bioavailable Te levels were negatively related to both age and AVF, without interaction between these variables. The LH response to a submaximal dose of GnRH was independent of age and AVF. Conclusion. Advancing age is associated with 1) attenuated bioavailable Te secretion caused by diminished GnRH outflow and not by decreased GnRH responsivity of the gonadotrope, 2) diminished testicular responsivity to infused LH pulses, and 3) partial compensation by diminished Te feedback on central gonadotropic regulation.

Reproductive performance of goats treated with free gonadorelin or nanoconjugated gonadorelin at estrus

The reproductive performance of goats that received a GnRH analog (gonadorelin) fabricated with or without chitosan-sodium tripolyphosphate (TPP) nanoparticles on the day of estrus (day 0) was evaluated. The chitosan-TPP polymer was conjugated with gonadorelin using an ionic gelation method. Thirty-three multiparous Zaraiebi goats were synchronized for estrus with 2 intramuscular (im) injections of 125 μg prostaglandin F2α 14 d apart. Goats showing signs of estrus were divided equally into 3 experimental groups and received a single im injection of 1 mL physiological saline (placebo; control), 50 μg/mL gonadorelin (GnRH), or 12.5 μg (quarter of GnRH dose)/mL chitosan-TPP–conjugated gonadorelin nanoparticles (NGnRH). Each goat underwent ultrasound imaging of their ovaries at day 0 and at day 10 after mating, and pregnancy was diagnosed 28 and 45 d after mating. The concentrations of estradiol (E2) and progesterone (P4) were determined at day 0 and at days 7, 14, 21, and 42 after mating. NGnRH size, polydispersity, and zeta potential were 93.91 nm, 0.302, and 11.6 mV, respectively. Chitosan-TPP nanoparticles showed 91.2% entrapment efficiency for GnRH. No differences in estrus rate, interval to estrus, or ovarian structure at day 0 were observed among the experimental groups, but the GnRH and NGnRH treatments significantly decreased the duration of estrus compared with the control. At day 10 after mating, both GnRH and NGnRH increased (P = 0.011) the number of corpora lutea compared with the control. Treatment with GnRH increased (P = 0.023) serum E2 concentrations from day 7 to 42 after mating compared with NGnRH and control treatments. The highest (P = 0.043) serum P4 concentration was observed in the GnRH group, followed by the NGnRH and control groups. The increase in serum P4 concentration started earlier a on day 7 in the GnRH group but later on day 14 in the NGnRH group. Compared with the control, GnRH resulted in a higher (P = 0.041) P4-to-E2 ratio, followed by NGnRH. Both gonadorelin treatments significantly increased the twinning rate, the number of embryos at days 28 and 42, and prolificacy and decreased pregnancy losses compared with the control. In conclusion, the administration of GnRH at the time of estrus improved the prolificacy of goats by increasing both the ovulation rate and the number of embryos. In addition, the nanoformulation developed in this study allowed a 75% reduction in the conventional dose of gonadorelin without affecting the fertility and prolificacy of goats, indicating the bioavailability of the reduced GnRH dose after conjugation with developed nanoformula.

216 Effects of low doses of GnRH at CIDR removal on estrus expression and conception rates in beef heifers

Abstract Previous studies evaluating single and multiple GnRH injections at time of CIDR removal have reported decreased interval to estrus and increased expression of estrus, and increased conception rates, respectively. Thus, the objective of this study was to compare the effects of supplementing GnRH at CIDR removal on expression of estrus and conception rates in beef heifers following the 7-d CO-Synch + CIDR protocol. Heifers (n = 1,482) from 11 herds over two years were synchronized using the 7-d CO-Synch + CIDR fixed time AI (FTAI) protocol and were randomly assigned to receive one of three treatments at CIDR removal [0 µg GnRH (0); 5 µg GnRH (5); or 5 µg at CIDR removal and 5 µg 12 h later (5 + 5)]. Expression of estrus and conception rates were analyzed using the GLIMMIX procedure of SAS with treatment as an independent variable and herd as a random effect. There was no effect of treatment on expression of estrus (P = 0.38), or AI conception rates (P = 0.85). There was an effect of estrus (P &lt; 0.01) and a treatment × estrus interaction (P = 0.02). Animals that exhibited estrus prior to FTAI had increased (P &lt; 0.01) conception rates compared with those that did not. Animals that exhibited estrus had increased (P &lt; 0.01) conception rates compared with non-estrus animals in the 0 and 5 + 5 µg groups (54 ± 3% vs 34 ± 3%, and 52 ± 3% vs 36 ± 3%, respectively), but in the 5 µg group, there was no difference (P = 0.53) in conception rates between estrus and non-estrus animals (44 ± 3% vs 41 ± 3%, respectively). In conclusion, estrus expression increased pregnancy success, but supplementation with 5 or 5 + 5 µg of GnRH at CIDR removal did not improve estrus response or conception rates in beef heifers.

Non-surgical artificial insemination using a GnRH analogue for ovulation induction during natural oestrus in African lions (Panthera leo)

Despite postulated potential for wildlife conservation, success of assisted reproduction techniques (ART) in ex-situ feline breeding remains <25%. The aim of this project was to develop a simplified, non-surgical artificial insemination (AI) protocol for African lions (Panthera leo), using an exogenous GnRH analogue to induce ovulation in females presenting natural oestrus, and minimizing manipulation of the animals. Four protocols were tested in five trained lionesses (3.5–8 years), for a total of 14 inseminations (2–4 per lioness). These protocols differed in the time lapse between GnRH injection and insemination, on days 4, 5, or 6 from onset of natural oestrus, determined by daily behavioural observation and vaginal cytology. Semen was collected from 8 different males by urethral catheterization and electro-ejaculation, during full anaesthesia. Females were immediately immobilized for AI after semen collection. After transrectal ultrasound examination of the reproductive tract, insemination was performed either intravaginal or transcervical using a commercial dog urinary catheter (2.0 × 500 mm, Buster®, Krusse, South Africa) with a metal stylet. A single intramuscular dose of exogenous GnRH (20 μg burserelin-acetate, Receptal®, MSD, Intervet, South Africa) administered 30 or 48 h before AI or during the AI procedure induced ovulation successfully, as all females entered either a non-pregnant luteal phase of 59.6 ± 0.95 days (n = 10) or a pregnant luteal phase of 111.7 ± 0.33 days (n = 3). However, the timespan between GnRH injection and end of behavioural and/or cytological oestrus differed widely (range: 0–120 h). The final pregnancy success rate was 33.3%.

Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep.

Simple SummaryThis study examines the preovulatory and ovulatory events (in terms of the timing of onset of estrus behavior, preovulatory LH surge, and ovulation) and the yields obtained (in terms of ovulation rate, progesterone secretion, and fertility) after insertion of controlled internal drug release (CIDR) devices for 5 days and treatment with equine chorionic gonadotrophin (eCG) or gonadotrophin-releasing hormone (GnRH).The present study examined, for meat sheep (Segureña breed; 2–5-years old, mean body score of 3.5 ± 0.5), the timings of onset of estrus behavior, preovulatory luteinizing hormone (LH) surge and ovulation, and the ovulation rate and fertility obtained after insertion of controlled internal drug release (CIDR) devices for 5 days plus treatment with equine chorionic gonadotrophin (eCG; single dose at CIDR removal, n = 19 ewes) or gonadotrophin-releasing hormone (GnRH, either in a single dose at 56 h after CIDR removal, group CIDR-GnRH, n = 19 ewes; or in one dose at CIDR insertion and another dose 56 h after CIDR removal, group GnRH-CIDR-GnRH, n = 19 ewes). In all the ewes, the appearance of estrus behavior ranged between 84% and 90% and all females showing estrus signs had subsequent preovulatory LH peaks and ovulations. Onset of these events was earlier in the CIDR-eCG group than in the CIDR-GnRH and GnRH-CIDR-GnRH groups (p < 0.05). These differences were mainly determined by the onset of estrus behavior, since timing and intervals of LH peak and ovulation were similar among treatments. In fact, the range of ovulations was narrower in the GnRH-CIDR-GnRH group, which suggests better synchronization of follicular growth (p < 0.05). In conclusion, protocols with two doses of GnRH offer similar yields to eCG protocols.