GnRH analogue triptorelin acetate induces ovulation in jennies during oestrus.

Most of the northern hemisphere donkey breeds are faced with the risk of extinction, thus donkey reproduction is considered an emerging branch of theriogenology, and the management of artificial insemination and induction of ovulation is a crucial point in setting up preservation protocols. For four consecutive cycles, six jennies' ovarian activity was routinely monitored; an ultrasound examination was performed daily from the evidence of a follicle diameter ≥27 mm until ovulation. Upon reaching a follicular diameter ≥32 ± 2 mm (Hour 0), oestrous jennies were treated alternatively with 0.1 mg triptorelin acetate, sc, (TRIP), 0.4 mg/sc of buserelin acetate (BUS) or saline, sc, (CTRL) and examined ultrasonographically at Hours 14, 24, 38, 42, 48, 62 and every 24 h until ovulation. Induction of ovulation was considered successful if ovulation occurred from 24 to 48 h after treatment. 11/12 cycles resulted in ovulation for TRIP and 12/12 for BUS and CTRL groups, respectively. Mean ± SD ovulation time after treatment was 37.3 ± 8.3, 47.1 ± 21.0 and 66.8 ± 25.9 h for BUS, TRIP and CTRL, respectively (p = .0032). Ovulation rates between h24 and h48 were 10/12 (83.3%) for both TRIP/BUS and 2/12 (16.7%) for CTRL, respectively (p = .003). Buserelin and triptorelin-treated jennies had a 25 times higher probability to ovulate between Hours 24 and 48 than controls (p = .003), while there were no jenny and cycle effects on the ovulatory rate. The results of this study show how triptorelin successfully induced ovulation in jennies, like other GnRH analogues previously evaluated.

Optimizing ReBreed21 I: Evaluation of endocrine and ovarian dynamics in non-bred Bos indicus heifers.

The present study evaluated follicular and endocrine dynamics during ReBreed21, a reproductive strategy that allows resynchronization of ovulation every 21 days in Bos indicus (Nelore) heifers. A synchronized estrous cycle was induced using a standard timed ovulation protocol (d -10: P4 implant inserted + 2 mg estradiol benzoate; d -2: P4 removed+ 0.5 mg cloprostenol + 0.6 mg estradiol cypionate + 200 IU equine chorionic gonadotropin (eCG); d0: 8.4 µg buserelin) without AI to ensure nonpregnancy in heifers. Day of GnRH was designated d0 of estrous cycle. On d12, heifers (n = 80) were randomized into three experimental groups: (1) ReBreed21 (n = 28) d12 P4 device inserted, d19 P4 device withdrawal plus 200 IU eCG, and d21 8.4 µg buserelin (GnRH); (2) ReBreed21+G (n = 26) same as ReBreed21 plus GnRH (16.8 µg) treatment on d12; and (3) Control (n = 26) no treatment. ReBreed21+G increased two-fold (62.9%; 18/26) percentage of heifers with synchronized follicular wave emergence compared to Control (34.6%; 9/26) whereas ReBreed21 (53.6%; 15/28) was intermediate. The ReBreeed21 groups (eCG on d19) increased (P < 0.01) follicular growth between d19 and d21 in ReBreed21 (2.3 ± 0.2 mm) and ReBreed21+G (3.4 ± 0.2 mm) compared with Control (1.2 ± 0.3 mm), resulting in greater (P < 0.01) follicle diameter on d21 for ReBreed21 (10.7 ± 0.4 mm) and ReBreed21+G (10.8 ± 0.4 mm) compared with Control (9.1 ± 0.5 mm). Structural luteolysis was similar among groups (P = 0.51), although the average day when P4 was <1 ng/mL was later (P < 0.01) for ReBreed21 (20.5 ± 0.2) and ReBreed21+G (20.7 ± 0.2) compared to Control (19.2 ± 0.4). Overall ovulation at the end of the estrous cycle was increased (P = 0.03) for ReBreed21 groups (83.3%; 45/54) compared with Control (57.7%; 15/26). Synchronized ovulation on day 22-23 was greater (P < 0.01) for ReBreed21 (78.6%; 22/28) and ReBreed21+G (76.9%; 20/26) compared with Control (30.8%; 8/26). Thus, the ReBreed21 resynchronization program produced acceptable endocrine and follicular dynamics, including synchronized ovulation at the end of the protocol in nonpregnant heifers providing good rationale for testing the fertility and practical implementation of this protocol under field conditions.

Endocrine changes induced by GnRH immunisation and subsequent early re-stimulation of testicular function with a GnRH agonist in stallions.

CONTEXT: Resumption of testicular function after gonadotrophin-releasing hormone (GnRH) immunisation varies among individual animals and some stallions regain fertility only after a prolonged time. AIMS: This study evaluated endocrine effects of GnRH immunisation and early subsequent re-stimulation with a GnRH agonist. We hypothesised that GnRH agonist treatment advances resumption of normal endocrine function in GnRH-vaccinated stallions. METHODS: Shetland stallions were assigned to an experimental and a control group (n =6 each). Experimental stallions were GnRH-immunised twice, 4weeks apart. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3ng/mL. Three weeks later, daily treatment with the GnRH agonist buserelin was initiated (4µg/day for 4weeks followed by 8µg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5ng/mL in vaccinated stallions. Blood was collected for LH, FSH, oestradiol and anti-müllerian hormone (AMH) analyses, and testicular and epididymal tissue were conserved for real-time qPCR and histology. KEY RESULTS: GnRH vaccination reduced blood concentrations of LH and FSH, with a structural deterioration of testicular tissue and disruption of spermatogenesis. Daily buserelin treatment for approximately 60days partially restored gonadotropin secretion and induced a recovery of the functional organisation of the testicular tissue with effective spermatogenesis. CONCLUSIONS: Endocrine testicular function can be restored in GnRH-vaccinated stallions by daily low-dose buserelin treatment. The buserelin treatment protocol may potentially be improved regarding the dose, interval and duration. IMPLICATIONS: Daily buserelin treatment can be recommended for treatment of GnRH-vaccinated stallions with prolonged inhibition of testicular function.

GnRH analogs induce a LH peak and increase pregnancy per timed-AI in ewes.

To date, there have been no studies testing the capacity of GnRH analogs and respective doses to induce a LH peak in sheep. In this sense, the present study aimed to evaluate the capacity of different synthetic forms and doses of GnRH in inducing LH release in sheep, and the effect of GnRH administration at timed artificial insemination (TAI) on pregnancy per timed-AI. In experiment 1, ewes (n = 40) received an intravaginal device (IVD) of medroxyprogesterone acetate (MPA; 60 mg) for 7 d and prostaglandin F2α analog on Day 5. On Day 7, the ewes were allocated randomly into one of eight groups (n = 5/group), which received a GnRH analog at a specific dose, as follows: lecirelin (12.5 or 25 µg), gonadorelin (50 or 100 µg), buserelin acetate (4.2 or 8.4 µg), or deslorelin (375 or 750 µg). Blood samples for LH determination were obtained at 0, 2, 4, and 6 h after GnRH and the IVDs were removed after the last blood collection. The maximal LH concentration induced by gonadorelin at doses of 50 µg and 100 µg (12.0 ± 2.4 ng/mL and 28.6 ± 7.1 ng/mL, respectively) was lower (P < 0.05) than serum LH induced by 8.4 µg of buserelin (78.9 ± 12.9 ng/mL), 375 µg and 750 µg of deslorelin (75.6 ± 7.4 ng/mL and 72.1 ± 10.6 ng/mL, respectively) and 12.5 µg and 25 µg of lecirelin (73.3 ± 17.8 ng/mL and 61.6 ± 5.9 ng/mL, respectively). However, the maximal LH concentration induced by 4.2 µg of buserelin (49.4 ± 5.9 ng/mL) was similar (P > 0.05) to the 100 µg of gonadorelin. The total release of LH (area under the curve - AUC) after treatment with 50 µg of gonadorelin (31.7 ± 5.9 ng h/mL) was lower (P < 0.05) than after other agonists. In a second experiment, 330 ewes were treated with IVD containing MPA for 7 d. Simultaneously with IVD removal, 250 µg of cloprostenol and 200 IU of eCG were administered. Then, ewes were assigned randomly to either no further treatment (control); or to receive 4.2 µg of buserelin acetate (GnRH group) at cervical TAI, which was performed with fresh semen 54 h after IVD withdrawal in all the animals. Higher pregnancy per timed-AI was observed for GnRH (50.3 %) compared to control (40.7 %). We conclude that buserelin acetate (8.4 µg), lecirelin (12.5 and 25 µg) and deslorelin (375 and 750 µg) induced a greater stimulatory effect on LH secretion than gonadorelin treatment. Furthermore, buserelin acetate treatment at TAI increased pregnancy per timed-AI in ewes previously treated with MPA and eCG.

Induced reproduction of yellow-tailed lambari (Astyanax lacustris) with Ovopel® and buserelin acetate as alternatives to the protocol with carp pituitary extract.

The objective of this study was to evaluate reproductive traits in adults of Astyanax lacustris subjected to different spawning inducers. The study involved 240 females (12.54 g ± 2.33 and 7.66 cm ± 0.63 cm) and 240 males (5.83 g ± 0.39 g and 6.14 cm ± 0.64 cm), all at reproductive age. Three different inducers were evaluated: (i) 0.4 pellets of Ovopel®/kg of body weight; (ii) 0.5 ml of buserelin acetate/kg of body weight; and (iii) carp pituitary extract (CPE) (5.5 mg CPE/kg body weight for females and 2.5 mg CPE/kg body weight for males), as well as saline solution (without hormone). The degree-hours for spawning were greater (P<0.05) for the Ovopel® treatment (with 204.93) than in the treatment with CPE (183.2). Ovary weight and gonadosomatic index were higher (P<0.05) in CPE and Ovopel® treatments when compared to buserelin acetate. The number of oocytes per female, absolute and relative fecundity were greater (P<0.05) for Ovopel® and CPE treatments. Fertilization rate was higher (P<0.05) in treatment with buserelin acetate (82.3%) in relation to Ovopel® (72.33%) and CPE (62.40%) treatments, and the highest (P<0.05) hatching rates were achieved with buserelin acetate and Ovopel®. The number of larvae per female body weight was greater (P<0.05) when Ovopel® was used. In conclusion, Ovopel® proves to be a more effective reproductive inducer for induced reproduction of A. lacustris when compared to CPE and buserelin acetate.

GnRH34 with or without estradiol cypionate in timed AI in Bos indicus beef cows.

Two experiments were performed to evaluate the effects of GnRH treatment on the fertility of suckled Nelore beef cows treated with an estradiol/progesterone (E2/P4)-based protocol for timed artificial insemination (TAI). Experiment 1 focused on determining the effects of estradiol cypionate (EC) on ovulation in TAI cows treated with GnRH 34 h after removal of the intravaginal P4 device (IPD). Suckled cows (n = 26) were treated with 2 mg estradiol benzoate (EB) and IPD containing 1 g P4. After 8 days, IPDs were removed, and all cows were treated with 150 µg of d-cloprostenol (prostaglandin F2 alpha analog) and 300 IU of equine chorionic gonadotropin (eCG), then separated into two treatment groups consisting of cows who received 1) saline 0.9% i.m. (GnRH34 group) or 2) 0.6 mg i.m. of EC (EC-GnRH34 group). On day 9 (05:00 p.m.), all cows were given GnRH (10.5 µg of buserelin acetate) i.m. No differences were observed between the groups (P > 0.05) in the time of ovulation after IPD removal or in the proportion of cows ovulating. Experiment 2 focused on determining the effects of GnRH34 along with or in the absence of EC on day 8 on pregnancy per AI (P/AI) in postpartum beef cows. Cows (n = 981) were treated similarly to those in Experiment 1, but an additional group, the EC-GnRH48 group, was included, in which cows received EC on day 8 whereas those that did not show estrus received GnRH at TAI. Thus, in this experiment, groups consisted of GnRH34 (n = 322), EC-GnRH34 (n = 335), and EC-GnRH48 (n = 324). A higher rate of estrus expression was observed in cows treated with EC following IPD removal (EC-GnRH34: 69%, EC-GnRH48: 64.8%) than in cows in the GnRH34 group (45.6%). No difference in P/AI was observed between the treatment groups (P = 0.45), but P/AI in cows in the EC-GnRH34 group (64.2%) tended to be greater (P = 0.1) than in cows in the GnRH34 group (58%). In summary, although ovulation synchrony did not differ among the groups, P/AI in cows treated with EC and GnRH 34 h after IPD removal tended to be greater than in cows treated solely with GnRH; this was most likely due to a shorter proestrus/estrus period, considering the lower proportion of cows that displayed estrus in the GnRH34 group. Finally, given that P/AI did not differ between the EC-GnRH34 and EC-GnRH48 groups, our results suggest that, for cows not displaying estrus, administration of EC at the time of IPD removal followed by treatment with GnRH 48 h afterward represents the most cost-efficient TAI strategy for South American Zebu-based beef operations.

Comparative study between efficacy of dexamethasone-prostaglandin-receptal combination and mechanical correction in uterine torsion cases in Egyptian buffalo-cows (Bubalus bubalis).

BACKGROUND: According to reports, the majority of domesticated species exhibited uterine torsion. It was occasionally noted as a cause of dystocia in buffaloes. The uterus might twist more frequently late in pregnancy because of certain animal traits. The current research monitored the clinical findings and laboratory assays associated with uterine torsion cases in pregnant buffalo-cows through comparing between normal labored buffalo-cows (Norm-Labgr; n = 20), mechanically corrected uterine torsed animals without medicament interference (UtrTorsgr; n = 160), and mechanically corrected uterine torsed animals with medicament interference (UtrTors-Medgr; n = 40) through focusing on placental characterization, calves body weight, milk constituents and milk somatic cell count (SCC) in normal labored buffaloes and uterine torsed ones. Through clinical and laboratory investigations of these buffaloes (N = 220) had been conducted 3 times; 7 h pre-calving and post calving (Post uterine correction) i.e. 48 and 96 h. Uterine torsion prevalence parameters, placental characterization, calves body weight, milk constituents and milk somatic cell counts were evaluated in normal labored buffaloes and uterine torsed ones. RESULTS AND CONCLUSIONS: The study concluded pre-calving remarkable variations in clinical findings, leukogram picture, calf birth weight and some placental characterization parameters between Norm-Labgr and each of UtrTorsgr and UtrTors-Medgr whereas these variations disappeared post-partum as a result to either only mechanical correction or mechanical correction plus medicaments interference. No pre-or post-calving significant changes between UtrTorsgr and UtrTors-Medgr except for the abnormal clinical findings were more representative in UtrTors-Medgr than those in UtrTorsgr particularly pre-calving. The applied pre-calving therapeutic regimen including dexamethasone-prostaglandin-receptal combination had a powerful potential efficacy that induced vaginal delivery of calves in UtrTors-Medgr as well as prepartum mechanical correction of torsed uterus approved higher efficacy in UtrTorsgr. The applied prepartum mechanical correction of torsed uterus and/or pre-calving therapeutic regimen as well as subsequent post-calving, post uterine correction applied medicament treatment accelerated rapid recovery of affected buffalo-cows through achieving rapid restoring of their physiological parameters. Buffalo-cow's milk composition, milk pH and milk SCC were not affected whereas no significant variations were reported between Norm-Labgr, UtrTorsgr and UtrTors-Medgr.

Intensity of estrus expression - valuable obvious determinant of fertility in Bos indicus cows.

This study aimed to characterize estrus response and to establish relationships between intensity of estrus, preovulatory follicle (POF) size and estradiol (E2) concentrations on day of AI, luteal profiles and pregnancy outcome in lactating Hariana breed of cows. 200 cyclic cows were subjected to Ovsynch (n = 54) and Pre-OV treatment (n = 146). Ovsynch: Buserelin acetate (BA; 10 µg), Cloprostenol (500 µg) and BA (10 µg) were injected i.m. on day 0, 7 and 9, respectively, irrespective of treatment. Pre-OV: BA (10 µg) and Cloprostenol (500 µg) was also injected i.m. simultaneously 7 days prior to initiate Ovsynch. On the basis of estrus behavior, the cows were classified into three groups: weak, moderate and intense. Artificial insemination performed at 18-24 hours after 2nd BA of Ovsynch in both treatments. The average duration of estrus did not differ (p > 0.05) between Ovsynch and Pre-OV treatment. A positive correlation was observed between estrus response and POF size, concentration of E2 on day of AI and luteal profiles on day 12 post-AI. First service conception rate was higher in cows exhibited intense (45.46%) and moderate (42.56%) estrus response than weak (28.57%) estrus response. In conclusion, intensity of estrus expression could be considered as important determinant for deciding pregnancy outcomes in Bos indicus cows.

Effect of repeated low doses of GnRH analogue (buserelin) on fertility performance of dairy cows with anovulation type I.

The aim of this study was to evaluate the fertility response of dairy cows with anovulation type I on repeated low doses of GnRH agonist buserelin. The study was conducted on 83 anovulatory and 60 cyclic Polish Holstein Friesian cows. Anovulation type I 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 from the experimental group (n=58) received 0.4 µg of buserelin i.m. once a day for 5 consecutive days. Cows from the negative control group (n = 25) received saline. Sixty cyclic cows receiving no treatment served as positive controls. Intervals from calving to estrus and from calving to conception, pregnancy rate 30-35 days and 260 days after AI, and pregnancy loss were calculated. The anovulatory cows had a substantially prolonged calving to conception interval, decreased pregnancy rate and increased pregnancy loss and culling rate compared to cyclic herd mates. The average calving to conception interval was significantly (p⟨0.05) shorter in treated cows compared to non-treated anovulatory cows (153.7 days vs 209.3 days). In conclusion, repeated low doses of GnRH analogue buserelin led to a significant shortening of calving to conception interval. More clinical trials are needed to determine the practical usefulness of this method for the treatment of anovulation type I in dairy cows.

Effect of the GnRH stimulation test on Canine Prostatic-Specific Esterase (CPSE).

The gonadotropin-releasing hormone (GnRH) stimulation test is used to investigate testicular production of testosterone (T) when performing a breeding soundness examination. In male dogs with fertility problems, the prostate should also be investigated as prostatic conditions may frequently lower semen quality. Serum concentrations of canine prostatic-specific esterase (CPSE) increase in dogs with benign prostatic hyperplasia (BPH). When performing a breeding soundness examination in a male dog, GnRH administration is frequently done at the beginning of the process and then both T and CPSE are assayed on the same serum sample collected 1 h following the GnRH injection. The aim of this study was to assess whether or not the administration of GnRH may alter CPSE concentrations in dogs with a healthy prostate. Twenty-eight client-owned intact adult male dogs were included in the study. Following a 7-day sexual rest all male dogs underwent a clinical examination and an ultrasonographic examination of the prostatic gland. Prostatic size and parenchyma of every tested dog were evaluated by ultrasonography to assess prostatic conditions. Two different GnRH stimulation protocols were used, A = gonadorelin 50µg/dog SC (n = 15) and B = buserelin 0.12 µg/kg IV (n = 13). T and CPSE concentrations were measured before and 1 h after GnRH administration by a laser-induced fluorescence analysis. Buserelin and gonadorelin were equally effective in causing a significant increase in serum T concentrations in the post GnRH sample. When considering the 28 dogs together, CPSE concentrations did not change following the stimulation test with either GnRH compound; however, in 4/28 cases, the post GnRH value was markedly increased to values compatible with a diagnosis of BPH. There was no difference in the action of buserelin or gonadorelin in causing an increase in serum T concentrations. CPSE secretion was increased in approximately 15% of dogs treated with either buserelin or gonadorelin. Therefore, whenever performing diagnostic testing in intact male dogs, CPSE should not be assayed on a post-GnRH serum sample.

Cardiovascular adverse events-related to GnRH agonists and GnRH antagonists: analysis of real-life data from Eudra-Vigilance and Food and Drug Administration databases entries.

INTRODUCTION AND OBJECTIVES: GnRH agonists and GnRH antagonists are two of the mainstays of hormonal therapy (HT) for prostate cancer (PCa). These drugs are at increased risk of cardiovascular (CV) adverse events (AEs). Aim of our study was to compare real-life data on AEs associated with GnRH agonists and GnRH antagonists based on Eudra-Vigilance (EV) and Food and Drug Administration (FDA) reported AEs. MATERIALS AND METHODS: EV and FDA databases were queried and the number of CV adverse events (AEs) for degarelix, buserelin, goserelin, leuprorelin, triptorelin until September 2021 were recorded. Specific CV AEs were recorded and data were analyzed per age and severity. pooled relative risk (PRR) was used to compare data between drugs. RESULTS: CV events were reported in 315/5128 (6%) for Degarelix, in 55/628 for Buserelin (9%), in 843/12,145 (7%) for Goserelin, in 3395/71,160 (5%) for Leuprorelin and in 214/4969 (5%) for Triptorelin. In terms of specific CV disorders, Degarelix presented lower risk of hypertension (PRR 0.60 (95% CI 0.37-0.98), p = 0.04), of myocardial infarction (PRR 0.05 (95% CI 0.01-0.39), p < 0.01) and thrombosis (PRR 0.14 (0.02-1.07), p = 0.06) when compared to GnRH agonists. Overall, younger patients (<65 years) presented a very low risk of CV AEs. Side effects were classified as serious in 90-96% of the cases. Fatal AEs were 5-20% over the CV AEs and 0.2-1% over the total AEs. CONCLUSIONS: Real-life data are consistent with registry studies regarding side effects related to HT. Real-life data suggest GnRH agonists are associated with higher CV AEs when compared to GnRH antagonists. Clinicians should consider these data when prescribing HT especially in patients with CV comorbidities.

Effect of increased serum progesterone on luteal morphology and function, pregnancy, and gestational loss in Nelore cows.

The aim of the present study was to determine the impact of different strategies for increasing the level of serum progesterone (P4) on luteal morphology and function in bovine females. The effects of increasing P4 on pregnancy rate and gestational loss (GL) in Nelore cows subjected to timed artificial insemination (TAI) were also evaluated. A total of 939 cows were divided into three groups: P4LA (n = 305), 150 mg of long-acting injectable P4 7 days after TAI; GnRH (n = 306), 10 µg of buserelin acetate 7 days after TAI; and control (n = 328), no hormone treatment after TAI. Doppler ultrasound assessments and P4 measurements were performed on days 7 and 16 after TAI. The pregnancy rate and GL as a function of treatment were compared using the SAS GLIMMIX procedure. Corpus luteum (CL) vascular perfusion, volume, and plasma P4 concentration were analysed using the SAS PROC MIXED procedure. No significant difference was found among the treatments in terms of volume, number of pixels, and CL intensity or in the serum P4 concentration at 7 days after ovulation. The CL blood flow at 16 days after ovulation was lower in the P4LA and GnRH groups than that in the control group (p < .01). Serum concentrations of P4 at 16 days after ovulation were higher in the P4LA and GnRH groups than those in the control group (p = .04). A difference in the pregnancy rate (p = .003) and a trend in GL (p = .07) as a function of treatment were found. Overall, long-acting injectable P4 supplementation on day 7 after TAI or GnRH administration affected CL vascularization and increased the serum concentrations of P4 16 days after ovulation, promoting better pregnancy rates than the control.

Presynchronization with simultaneous administration of GnRH and prostaglandin F2α (PGF2α) 7 days prior to Ovsynch improves reproductive profile in Hariana zebu cow.

This study is aimed at assessing the impact of simultaneous administration of GnRH and prostaglandin F2α (PGF2α) 7 days prior to Ovsynch in Hariana cow. Two hundred cyclic cows (> 4 months postpartum) were assigned to control (n = 54) and pre-OV (n = 146). As per Ovsynch protocol, buserelin acetate (10 µg), cloprostenol (500 µg), and buserelin acetate (10 µg) were injected i.m. on days 0, 7, and 9, respectively, in cows irrespective of treatment. But in pre-OV cows, buserelin acetate (10 µg) and cloprostenol (500 µg) were also injected i.m. simultaneously 7 days prior to initiate the Ovsynch protocol. Artificial insemination was performed between 18 and 24 h after the 2nd GnRH of Ovsynch in both treatments. Ultrasonography and blood sampling for hormonal analysis were done on each day of treatment, on day of AI, and 12 days post-AI. Pre-OV treatment resulted to increased (45.20% vs 29.62%; P < 0.05) pregnancy outcomes and higher (P < 0.01) ovulation rate to first GnRH of Ovsynch than control. Cows showing complete luteolysis in response to PGF2α of Ovsynch were also higher (P < 0.05) in pre-OV than control. Greater (P < 0.05) synchronization rate was recorded in pre-OV than control (86.76% and 68.75%). The circulating concentrations of estradiol on day of AI and progesterone on day 12 post-AI were higher (P < 0.01) in cows diagnosed pregnant than non-pregnant in both control and pre-OV treatment. In conclusion, simultaneous administration of GnRH and PGF2α 7 days before Ovsynch improved the synchronization rate and luteal profile in terms of CL area and hence resulted in higher conception rate in Hariana zebu cow.

Re-stimulation of testicular function in GnRH-vaccinated stallions by daily GnRH agonist treatment.

In stallions temporarily not intended for breeding, reversible suppression of testicular function by vaccination against GnRH can be of interest. In the present study, effects of GnRH agonist treatment on the resumption of testicular function after GnRH vaccination were investigated. Testis size, testosterone release, semen characteristics and behavior were evaluated. We hypothesized that GnRH agonist treatment would restore testicular function. Shetland stallions were assigned to an experimental and a control group (n = 6 each). Experimental stallions were GnRH-immunized twice, four weeks apart. Ejaculates for semen analysis and blood for analysis of testosterone concentration and GnRH antibody titers were collected. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3 ng/mL. Three weeks thereafter, daily treatment with the GnRH agonist buserelin was initiated (4 µg/day for 4 weeks followed by 8 µg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5 ng/mL in vaccinated stallions. Time from exposure to a mare until mounting increased in GnRH-vaccinated stallions and decreased with buserelin treatment. Total sperm count decreased after vaccination but increased only slightly in response to buserelin. Sperm motility and percentage of membrane-intact spermatozoa decreased after vaccination and returned to pre-vaccination values with buserelin treatment. Testosterone concentration and testis volume decreased after GnRH vaccination and started to increase with buserelin treatment. In conclusion, the downregulation of testicular function by GnRH vaccination can be counteracted with buserelin. This approach may be useful in GnRH-vaccinated stallions with prolonged suppression of testicular function.

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.

Mitigation of low pregnancy rate in excitable Nellore cows by administration of GnRH or P4.

This research aimed to determine the effect of temperament on reproductive parameters including cortisol and progesterone (P4) in Nellore cows. Additionally, two methods for increasing plasma progesterone (P4) levels in excitable animals to enhance pregnancy rate (P/AI) and reduce pregnancy loss were investigated. In total, 939 cows were subjected to timed artificial insemination (TAI) and divided into three groups: (P4LA; n = 305) 150 mg of injectable long-acting progestogen 7 days after TAI; (GnRH; n = 306), 10 µg of buserelin acetate on day 7 after TAI; control group (CG; n = 328) without hormonal treatment. In 213 cows, randomly chosen from each group, ultrasound evaluations of the preovulatory follicle (Mode B) were performed on the day of insemination and of the corpus luteum (Color Doppler) 7 and 16 days after TAI. Blood samples were obtained from 20% of the 939 animals, randomly chosen from each group, on the day of insemination and after 7 and 16 days to measure cortisol and progesterone, respectively. At the time of insemination, subjective temperament evaluations were performed with the animals being classified as excitable (EXC) or adequate (ADQ). The SAS GLIMMIX procedure was used to compare the pregnancy rate (P/AI) and gestational loss within each temperament for the three experimental groups. Continuous variables were analyzed utilizing SAS PROC MIXED procedure. Cortisol concentration was higher and POF (preovulatory follicle) and CL (corpus luteum) volumes at the time of insemination and 7 days after AI, respectively, were lower in EXC animals than in ADQ. No significant difference was observed between the number of pixels, CL intensity, and plasma concentration of P4, 7 days after TAI. However, 16 days post-insemination, among the animals classified as EXC, higher concentrations of P4 were observed in the GnRH and P4LA groups than in the control. Regarding P4 concentrations, there was a tendency to be lower in animals classified as EXC than in ADQ within the control group (P = 0.06), while rate of blood flow from the CL was lower in EXC animals than in ADQ animals (P = 0.04). Among the ADQ animals, the GnRH and P4LA groups showed a lower CL flow rate than that observed in the control (P = 0.04), 16 days after the TAI. Among EXC animals, a higher pregnancy rate was observed in the GnRH and P4LA groups than in the control group (P = 0.01). In the control group, the pregnancy rate (P/AI) of the ADQ animals was higher than that of the EXC animals (P = 0.05). No statistically significant differences were observed between gestational losses when the treatments or temperaments were compared. In conclusion, the use of GnRH or P4LA, 7 days after insemination, improves pregnancy rates in excitable animals and is a viable alternative to minimize the negative impact of stress and improve reproductive efficiency in beef cattle.

Gilt reproductive performance in a tropical environment after oestrus synchronization and fixed-time artificial insemination.

The present study was performed to evaluate the reproductive performance of gilts inseminated using fixed-time artificial insemination (FTAI) protocol. A total of 408 Landrace × Yorkshire crossbred gilts were included in the experiment. Gilts at 8 months of age were randomly allocated into three groups: control AI (n = 192), treatment 1-TAI (n = 117) and treatment 2-FTAI (n = 99). Gilts in the control AI group were inseminated 2-3 times during standing oestrus at 0, 12 and 24 h after the onset of oestrus. Gilts in the treatment 1-TAI group were orally administered 20 mg per day of altrenogest for 18 days and then inseminated 2-3 times during standing oestrus by conventional AI. Gilts in the treatment 2-FTAI group were synchronized like gilts in treatment 1-TAI group but then GnRH (10 µg of buserelin) was administered 120 h after the end of altrenogest treatment and fixed time artificial inseminated twice at 24 and 32 h after GnRH irrespective of the presence of oestrus or not. Conception rate of gilts in treatment 2-FTAI (87.9%) was similar to the treatment 1-TAI (94.9%) and control AI (83.3%) (P > 0.05). Conception rate in treatment 1-TAI (94.9%) was higher compared to control AI group (83.3%, P = 0.040). Farrowing rate of gilts in treatment 2-FTAI (83.8%) was similar to treatment 1-TAI (89.7%) and control AI (76.0%) (P > 0.05). Farrowing rate of treatment 1-TAI (89.7%) was higher than control AI gilts (76.0%, P = 0.033). In treatment 2-FTAI, the conception and farrowing rate of the nine gilts that were inseminated even if they were not detected in oestrus (all during warm season) was 44.4% and 44.4%, respectively. Regular return to oestrus was similar between groups (9.4%, 0.9% and 4.1% for control AI, treatment 1-TAI and treatment 2-FTAI, respectively, P > 0.05). The total number of piglets born per litter in treatment 1-TAI group was higher than control AI (13.1 ± 0.2 versus 11.6 ± 0.2, respectively, P < 0.001) and treatment 2-FTAI groups (12.2 ± 0.3, P = 0.019). The number of piglets born alive was higher in treatment 1-TAI (12.1 ± 0.3) compared to treatment 2-FTAI (11.3 ± 0.2) and control AI group (11.2 ± 0.3). The percentage of stillbirth and mummified foetus were not different between groups (P > 0.05). The present study indicated that fixed-time AI in gilts can be successfully performed by administration of altrenogest for 18 days, GnRH at 120 h after altrenogest withdrawal and then double fixed-time AI at 24 and 32 h after the administration of GnRH. Fertility metrics such as conception rate, farrowing rate and litter performances using this method were similar to gilts inseminated at oestrus with conventional AI.

Reproductive efficiency of sows inseminated at single dose fixed time with refrigerated, cryopreserved and encapsulated spermatozoa.

The aim was to assess the reproductive efficiency of different techniques used to preserve spermatozoa in artificial insemination semen doses (AI-doses) by evaluating refrigeration at 15°C, cryopreservation and encapsulation. Forty-two hyperprolific sows were treated with buserelin and inseminated once at a single fixed time. The fertility rate, embryonic vesicles viability and the early embryonic mortality (arrested conceptuses) evaluated post-mortem at 24th day of pregnancy, were analysed in order to assess the effectiveness of each proposed technique. Results show an overall reduction on fertility using the three proposal sperm preservation techniques (69.27%, 60.00% and 78.75% for refrigerated, frozen-thawed and encapsulated AI-doses, respectively). Total number of embryonic vesicles was very similar among the three treatments; yet, the number of viable vesicles was numerically different among groups, and thus, embryonic viability was 79.25%, 80.0% and 87.15% for refrigerated, frozen-thawed and encapsulated AI-doses, respectively.

The Kisspeptin analogue C6 induces ovulation in jennies.

Kisspeptins (KPs) are the most potent stimulating neurotransmitters of GnRH release, and consequently KP administration triggers LH and/or FSH release. In small ruminants, KP or its analogs induced an LH surge followed by ovulation in both cyclic and acyclic animals, while in the mare KP only increased LH plasma levels but failed to induce ovulation. This study in jennies compares the endocrinological effects, ovulatory and pregnancy rates of the KP analog C6 and the GnRH analog buserelin acetate. The ovarian activity of nine Amiata jennies was monitored daily by transrectal ultrasound for three complete estrous cycles. Jennies in estrus were assigned, to one of three treatment groups: 50 nmol of the KP analog C6 (injected twice, 24 h apart, C6 group); 0.4 mg buserelin acetate (injected once, Bu group); and 2 mL of saline (injected once, CTRL group). Blood samples were collected at Day-1 (-24 h) Day0 (h0, before treatment), h2, h4, h6, h8, h10, h24 (before second treatment with C6), h26, h28, h30, h32, h34, h48 and every 24 h until ovulation. Jennies were inseminated once at h24 with fresh extended semen from a donkey stallion. Pregnancy diagnoses were performed 14 days after ovulation. On days 5, 10, and 14 after ovulation, for every CL the cross-sectional area (CSA) and the vascularized area (VA) were recorded by color doppler ultrasound and measured. Significantly higher plasma LH levels were found after induction between the Bu and CTRL groups at h6 and h8 (P < 0.05), while tendentially higher differences were found between the Bu/C6 groups and CTRL at h10. Five/9, 4/9, and 2/9 jennies ovulated between 24 and 48 h after induction from the Bu, C6, and CTRL groups respectively, (P > 0.05). Correlations between corpora lutea CSA and VA with serum progesterone concentration were r = 0.31, P = 0.01, r = 0.38, P = 0.01, respectively. Pregnancy rates after artificial insemination did not differ among groups (CTRL: 6/9, 66.7%; C6: 7/9, 77.8%; Bu: 6/9, 66.7%; P > 0.05). Ovulation rates after C6 treatment were comparable to that of Bu, although not different from the CTRL. Pregnancy rates were comparable to the literature in terms of fresh extended donkey semen in every group. This study suggests that stimulation of the Kp system in jennies, in contrast to findings observed in mares, induces ovulation. Further studies using higher doses and/or more animals are needed to better characterize the efficacy of C6 in jennies.

LH pattern and ovarian response in ovsynch-synchronized superovulated goats induced to ovulate with GnRH or hCG.

The intention of the present investigation was to compare a GnRH agonist and hCG as ovulation inducing agents to apply fixed-time insemination in ovsynch synchronized superovulated goats. Three groups of 17 does of the Boer goat breed were synchronized, superovulated and ovulation induced with a GnRH analog, hCG or physiological saline, followed by mating and non-surgical embryo collection. Part of the does were provided with subcutaneous progesterone implants after mating to compensate for frequently occurring premature corpus luteum regression. Estrus detection was conducted with aproned bucks, ovarian function was monitored sonographically and by progesterone analyses and blood samples were drawn to generate LH profiles. Practically all does responded to treatment and occurrence and duration of estrus as well as the ovulatory response were unaffected by treatment. The LH surge provoked by administration of the GnRH analog buserelin emerged within 1.0 h and was closely synchronized, significantly more so than after administration of hCG or physiological saline, commencing after 11.8 and 14.9 h, respectively, with no significant differences amongst each other. It would seem that hCG is not effective in bringing about a LH surge. The interval between commencement of the LH surge and ovulation was, across treatment groups, 24.2 h with no significant difference among groups. Ovulatory response and yield of transferable embryos obtained by nonsurgical collection were modest with no significant differences among groups.