Prostaglandin F2α treatment does not hasten ovulation in weaned sows.

This study evaluated the efficiency of prostaglandin F2α (PGF) to hasten ovulation in weaned sows. In experiment I, weaned sows detected in estrus (0 h) received: no hormone (Control; n = 56); 0.5 mg PGF IM at 0 h and 2 h (PGF0; n = 56); or 0.5 mg PGF IM at 24 h and 26 h (PGF24; n = 55). In experiment II, weaned sows that did not express estrus signs until 72 h after weaning (0 h) were assigned to: no hormone (Control; n = 45); 10 µg buserelin acetate IM at 0 h (Buserelin; n = 43); 0.5 mg PGF IM at 34 h and 36 h (PGF; n = 44); or 10 µg buserelin acetate IM at 0 h plus 0.5 mg PGF IM at 34 h and 36 h (Buserelin + PGF; n = 45). In experiment I, no effect of PGF on the interval treatment onset to ovulation was observed (P > 0.05), and no treatment effect was observed on the relative or cumulative proportion of females that ovulated post-treatment onset (P > 0.05). In experiment II, treatment onset to ovulation interval was shorter for Buserelin group than for PGF group (P < 0.05), and a higher cumulative percentage of Buserelin treated sows ovulated up to 48 h compared to PGF and Control groups (P < 0.01), with no differences from Buserelin + PGF. Treatments did not affect total number of piglets born in both experiments (P > 0.05). In conclusion, PGF did not hasten ovulation timing or affect litter size in weaned sows.

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.

Effect of treatment of phantom cows with a progesterone-based synchrony programme.

Aim: To determine the effect of a progesterone-based synchrony programme on the daily hazard of conception and the probability of being pregnant at the end of the seasonal mating period in cows not observed in oestrus within 35-49 days of insemination and that were diagnosed non-pregnant (phantom cows) on seasonally calving New Zealand dairy farms. Secondary aims were to determine the prevalence of phantom cows and estimate the proportion of phantom cows with a functional corpus luteum (CL) at enrolment. Methods: Phantom cows from 14 New Zealand commercial dairy farms were enrolled in a randomised, controlled trial. Cows that were artificially inseminated ≤14 days after mating start date and were not subsequently detected in oestrus, were presented for pregnancy diagnosis approximately 49 days after mating start date. Non-pregnant cows were diagnosed as phantom cows and randomly allocated to treatment and control groups. A milk sample was collected for progesterone assay to determine the presence of a functional CL. Treatment consisted of an injection of buserelin and insertion of an intravaginal device containing progesterone on Day 0, injections of dinoprost and equine chorionic gonadotrophin, and removal of the intravaginal device on Day 7, injection of buserelin on Day 9, and fixed time artificial insemination on Day 10. Treatment group cows were then mixed with bulls for the remainder of the seasonal mating period. Cows allocated to the control group were mated naturally by bulls. Statistical models were constructed to determine the effect of treatment on the daily hazard of conception and the probability of being pregnant at the end of the seasonal mating period. Results: A total of 378/4,214 (9.0%) cows presented for pregnancy diagnosis were diagnosed as phantom cows. A functional CL was diagnosed in 257/362 (71.0%) phantom cows. Median predicted enrolment to conception intervals were 33 (95% CI = 30-45) and 30 (95% CI = 28-33) days, for cows in the control and treatment groups, respectively. The odds of being pregnant at the end of mating were 1.70 (95% CI = 1.34-2.17) times greater for treated phantom cows than untreated phantom cows. Estimated marginal mean proportion pregnant at mating end date were 59.5 (95% CI = 47.9-70.1)% and 71.5 (95% CI = 62.6-79.0)% for control and treatment group cows, respectively. Conclusions: Treatment with a progesterone-based synchrony programme significantly increased the probability of phantom cows being pregnant at the end of the seasonal mating period.

Progesterone-based timed AI protocols for Bos indicus cattle II: Reproductive outcomes of either EB or GnRH-type protocol, using or not GnRH at AI.

The aim of these experiments was to study ovarian dynamics and fertility of Bos indicus beef cattle submitted to 7-d progesterone (P4)-based fixed-time AI (FTAI) protocols using different hormonal treatments. In Exp. 1, 2 yr old Nelore heifers (n = 973) were randomly assigned to one of four treatments: EB-0 (estradiol benzoate, EB on D0 and no GnRH at AI), EB-G (EB on D0 and GnRH at AI), G-0 (GnRH on D0 and no GnRH at AI), or G-G (GnRH on D0 and at AI). On D0, heifers received an intravaginal P4 implant (0.5 g) for 7 d and EB (1.5 mg) or GnRH (16.8 µg). On D7, the P4 implant was withdrawn and heifers received cloprostenol (PGF; 0.5 mg) and estradiol cypionate (EC, 0.5 mg). Heifers in G groups also received PGF and eCG (200 IU) on D6, whereas EB heifers received eCG on D7. At FTAI on D9, only EB-G and G-G groups received GnRH (8.4 µg). In Exp. 2, Nelore cows (n = 804) received the same treatments (EB-0, EB-G, G-0, or G-G) using a 1.0 g P4 implant, 2.0 mg EB, and 300 IU eCG. Effects were considered significant when P ≤ 0.05. After treatment on D0, G had more ovulations than EB in heifers (60.3 [287/476] vs. 12.7% [63/497]) and cows (73.7 [83/112] vs. 24.4% [28/113]). Luteolysis after D0 was greater in EB than G in heifers (39.2 [159/406] vs. 20.0% [77/385]) and cows (25.5 [14/55] vs. 1.6% [1/64]). Heifers in G had larger follicles (mm) than EB on D7 (10.3 ± 0.2 vs. 9.2 ± 0.2) and at AI (11.9 ± 0.2 vs. 11.3 ± 0.2). Cows had larger follicles in G than EB on D7 (11.0 ± 0.3 vs. 9.9 ± 0.3) but not at AI. More estrus was observed in G than EB for heifers (80.3 [382/476] vs. 69.6% [346/497]) and cows (67.6 [270/400] vs. 56.2% [227/404]). There was no interaction between D0 and D9 treatments on pregnancy per AI (P/AI) in heifers (EB-0: 56.7 [139/245], EB-G: 53.6 [135/252], G-0: 52.6 [127/241], and G-G: 57.5% [135/235]). However, cows from EB-G had greater P/AI than EB-0 (69.5 [142/204] vs. 60.2% [120/200]), whereas P/AI for G-0 (62.7% [127/203]) was similar to G-G (60.9% [120/197]). In heifers, there was no interaction of GnRH at AI with estrus, however, cows that did not display estrus had greater P/AI if they received GnRH at AI (GnRH = 59.1 [91/154] vs. No GnRH = 48.2% [78/162]). Thus, protocols initiated with EB or GnRH for Bos indicus heifers and cows had differing ovarian dynamics but similar overall fertility, enabling their use in reproductive management programs. Treatment with GnRH at time of AI increased fertility in some instances in Bos indicus cows but not in heifers.

Single injection of triptorelin or buserelin acetate in saline solution induces ovulation in mares the same as a single injection of hCG.

The aim of this study was to assess the efficacy of different doses of buserelin acetate and another GnRH agonist, triptorelin acetate, in saline solution in a single subcutaneous injection, to induce ovulation of growing pre-ovulatory follicle in mare and compare it with the classical treatment of a single injection of hCG. The study is split into 3 experiments over different breeding seasons in the same stud with a random distribution of treatment. The first one was to compare the injection of 6 mg of buserelin with 1,500 IU of hCG; the second one consisted of comparing different doses of buserelin (6 mg and 3 mg); and the third one compared three different doses of buserelin (3, 2 and 1 mg), 0.1 mg of triptorelin with 1,500 IU of hCG as a control group. The results of all experiments showed the same efficacy between all treatments with mares ovulating between 24 and 48 hr after injection: experiment 1: hCG (78% n = 41) and buserelin 6 mg (90% n = 50); experiment 2: buserelin 6 mg (78,1% n = 192) and buserelin 3 mg (78% n = 341); and experiment 3: hCG (87% n = 106), buserelin 3 mg (84,7% n = 137), buserelin 2 mg (82,7% n = 104), buserelin 1 mg (87% n = 54) and triptorelin 0.1 mg (84,7% n = 72). In conclusion, this study contributes to erasing the dogma that has been established since 1975 that a single injection in solution without any long-acting excipient of a GnRH agonist cannot induce ovulation in the mare. This study also shows that a injection of 0.1 mg of triptorelin in solution is a good alternative for ovulation induction and is comparable to small doses of buserelin acetate in solution (1 mg) and 1,500 IU of the gold standard trigger hCG, mainly in countries where human formulation of buserelin is not available.

Association of pregnancy per artificial insemination with gonadotropin-releasing hormone and human chorionic gonadotropin administered during the luteal phase after artificial insemination in dairy cows: A meta-analysis.

One strategy for improving fertility in cattle is administration of GnRH or human chorionic gonadotropin (hCG) during the luteal phase, which increases progesterone (P4) secretion and delays luteolysis. To provide an overview of how GnRH or hCG treatment between 4 and 15 d after artificial insemination (AI) improves pregnancy per AI (P/AI) in cows, a meta-analysis was performed on 107 different trials from 52 publications. Data from 18,082 treated cows and 18,385 untreated controls were meta-analyzed. The meta-analysis explained the relative risk for P/AI with GnRH or hCG treatment under various circumstances. The results did not show any difference in P/AI between cows treated with hCG and cows treated with GnRH. Compared with no treatment, treatment with GnRH or hCG improved the chances of P/AI in cows with very poor (<30%) and poor (30.1 to 45%) fertility, whereas treatment did not benefit cows with very good fertility (>60.1%). Moreover, treatment with GnRH and hCG improved the chances of P/AI in primiparous cows. The improvement was much better in primiparous cows with very low fertility. Treatment with buserelin at a dose above 10 µg and with hCG at a dose above 2,500 IU was associated with increased chances of P/AI compared with lower doses. Treatment with GnRH 10 d after AI was also associated with increased chances of P/AI compared with earlier treatment. The present meta-analysis showed that the use of GnRH and hCG after AI should be focused on cows expected to have low or moderate fertility. Day and dose of treatment have to be considered as well.

Evaluation of uterine receptivity after gonadotropin releasing hormone agonist administration as an oocyte maturation trigger: a rodent model.

In natural cycle or minimal stimulation cycle IVF, buserelin acetate (buserelin), a gonadotropin-releasing hormone agonist, is often used as a maturation trigger; however, its effect on pregnancy outcomes remains unclear. Therefore, in the present study, we compared uterine receptivity in buserelin-administered mice with that in human chorionic gonadotropin (hCG)-administered mice during the peri-implantation period. Implantation, decidualisation, and term-pregnancy were impaired following hCG, but not buserelin administration. hCG stimulated the synthesis and secretion of progesterone and oestradiol, whereas ovarian steroidogenesis in the buserelin-treated group was comparable with that in the control group. Furthermore, similar to the observation in controls, the buserelin-treated group exhibited activation of progesterone receptor signalling and inhibition of oestrogen receptor signalling in the endometrial epithelium on the day of implantation. However, epithelial progesterone signalling was not detected, and a high expression of genes downstream to oestrogen was observed on day 4 following hCG administration. These results suggest that buserelin administration does not impact uterine receptivity as it did not affect ovarian steroidogenesis and endometrial steroid signalling. Therefore, buserelin is preferred as an oocyte maturation trigger to optimise uterine receptivity during treatments involving timed intercourse, intrauterine insemination, or fresh embryo transfer following in vitro fertilisation.

Use of cabergoline and post-collection GnRH antagonist administration for prevention of ovarian hyperstimulation syndrome.

RESEARCH QUESTION: Does the addition of a gonadotrophin-releasing hormone (GnRH) antagonist to cabergoline treatment during the luteal phase in fresh IVF cycles triggered with a GnRH agonist, and planned for freeze-all, reduce the rate of mild and moderate ovarian hyperstimulation syndrome (OHSS)? DESIGN: Retrospective cohort study of 480 IVF patients at risk for OHSS with GnRH agonist trigger from 2011 to 2018, stratified into three groups based on treatment received: GnRH agonist trigger alone (Group 1, n = 208), GnRH agonist trigger + cabergoline (Group 2, n = 167) or GnRH agonist trigger + cabergoline + GnRH antagonist (Group 3, n = 105). Data on patient demographics, incidence, severity and symptomatology of OHSS and laboratory findings were collected. RESULTS: Group 1 had more free peritoneal fluid than Group 2 (28% versus 19%, P = 0.04) or Group 3 (28% versus 5%, P = 0.001). Group 1 reported abdominal discomfort and bloating more than Group 2 (33% versus 21%, P = 0.01) or Group 3 (33% versus 18%, P = 0.006). Group 1 had more electrolyte abnormalities than Group 2, who had more than Group 3. No patients developed severe OHSS. Mild and moderate OHSS rate was higher in Group 1 (38%) than Group 2 (29%, P = 0.048) or Group 3 (18%, P = 0.006) and in Group 2 than Group 3 (P = 0.046). CONCLUSION: Addition of cabergoline to GnRH agonist triggering in high-risk OHSS patients, and subsequent addition of GnRH antagonist for 5 days in the luteal phase, sequentially reduces the risk of mild and moderate OHSS and improves patient comfort compared with GnRH agonist trigger alone.

Hot-Melt Preparation of a Non-Biodegradable Peptide Implant: A Proof of Principle.

BACKGROUND: Both biodegradable and non-biodegradable peptide-loaded implants are already developed for the long-term treatment of patients, thereby reducing the frequency of drug administration. To further improve peptide formulation, extending the scope of implant-based drug delivery systems towards other polymers and processing techniques is highly interesting. OBJECTIVE: In this study, as a proof-of-principle, the feasibility of hot-melt processing of a peptide active pharmaceutical ingredient was assessed by developing a non-biodegradable poly(ethylenevinyl acetate) (33% VA) implant loaded with 20% (w/w) buserelin acetate. METHODS: Cross-sectional implant characterization was performed by Raman microscopy. The stability of buserelin acetate in the polymeric matrix was evaluated for 3 months under ICH stability conditions and the quantity as well as the degradation products analyzed using LC-UV methods. An in vitro dissolution study was performed as well and buserelin acetate and its degradants analyzed using the same chromatographic methods. RESULTS: No significant quantities of buserelin acetate-related degradation products were formed during the hot-melt preparation as well as during the stability study. Together with the consistent buserelin acetate assay values over time, chemical peptide stability was thus demonstrated. The in vitro buserelin acetate release from the implant was found to be diffusion-controlled after an initial burst release, with stable release profiles in the stability study, demonstrating the functional stability of the peptide implant. CONCLUSION: These results indicate the feasibility of preparing non-biodegradable peptide-loaded implants using the hot-melt production method and may act as a proof of principle concept for further innovation in peptide medicinal formulations.

Second prostaglandin F2α treatment during Ovsynch protocol does not improve fertility outcomes in dairy cows.

The objective of this study was to evaluate the effect of a second prostaglandin F2α (PGF2α) treatment during Ovsynch on luteal regression and fertility in dairy cows, compared with standard Ovsynch. The study was conducted on 111 Holstein Friesian multiparous cows on commercial dairy farm. The cows in the experimental group (n=48) received two treatments of PGF2α 24 hours apart during Ovsynch. The cows in the control group (n=63) were synchronized with standard Ovsynch. To assess the progesterone (P4) concentration blood samples were collected at the day of PGF2α treatment and at the 2nd GnRH treatment. Pregnancy was evaluated by ultrasound examination 37-40 days after timed artificial insemination (TAI) by ultrasound. Cows diagnosed pregnant were re-examined between days 70-80 after TAI. The percentage of cows with complete corpus luteum (CL) regression (P4⟨0.5 ng/ml at the time of the 2nd GnRH treatment) was 89.6 % after two PGF2α treatments and 88.9 % after one PGF2α treatment. There were no statistically significant differences (p>0.05) in the pregnancies per artificial insemination (P/AI) between the experimental and control group (P/AI). However, the pregnancy loss rate was lower in cows receiving two PGF2α treatments than in the control animals (0.0 % vs. 6.4 %; p⟨0.05). In conclusion, the second PGF2α treatment during Ovsynch protocol had no significant effect on CL regression and P/AI in dairy cows. The pregnancy losses until days 75-80 after TAI were significantly lower after two PGF2α treatments than after one PGF2α treatment.

Response to ovulation trigger is correlated to late follicular phase progesterone levels: A hypothesis explaining reduced reproductive outcomes caused by increased late follicular progesterone rise.

STUDY QUESTION: Is there an association between progesterone (P4) levels on the day of hCG or GnRH trigger and on the day of oocyte retrieval in IVF/ICSI cycles? SUMMARY ANSWER: A significant positive correlation between P4 levels on the day of trigger and the day of oocyte retrieval is seen; HCG trigger induces a steeper P4 increase than GnRHa trigger. WHAT IS KNOWN ALREADY: FSH induces LH receptor (LHR) expression on granulosa cells, and LHR produces progesterone when exposed to LH-like activity. FSH per se also to some extent induces P4 secretion. Late follicular phase progesterone rise has been associated with reduced reproductive outcomes. STUDY DESIGN, SIZE, DURATION: This study is based on data from a previously published RCT conducted from 2009 to 2011. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 384 participants were enrolled; 199 received 5000 IU hCG and 185 received buserelin 0.5 mg for triggering ovulation. P4 was measured on the day of ovulation induction and on the day of oocyte retrieval. FSH consumption and number of retrieved follicles were recorded. MAIN RESULTS AND THE ROLE OF CHANCE: A significant linear relationship between P4 on the day of ovulation induction and oocyte retrieval was seen in the hCG trigger group (P < 0.00001) as well as in the GnRHa trigger group (P < 0.00001). The P4 ratio (the increase in P4 between ovulation induction and oocyte retrieval) was significantly higher in the group of patients with <5 follicles compared to those with 5-15 and >15 follicles (P < 0.0001). The FSH consumption per follicle was significantly higher in the group of patients with <5 follicles compared to those with 5-15 and >15 follicles (P < 0.0001). LIMITATIONS, REASONS FOR CAUTION: Although the study demonstrates a significant correlation between P4 levels before and after ovulation trigger, it does not demonstrate a causal relation to the number of LHRs present on granulosa cells. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this study support the proposed hypothesis that follicles exposed to high levels of FSH during ovarian stimulation will respond with an inappropriately high LHR expression. This in turn causes a high P4 output in response to the trigger. This study further expands our understanding of the underlying mechanisms affecting reproductive outcomes in relation to ovarian stimulation. STUDY FUNDING/COMPETING INTEREST(S): The authors received no specific funding for this work and disclose no conflicts of interest. TRIAL REGISTRATION NUMBER: N/A.

The impact of HCG in IVF Treatment: Does it depend on age or on protocol?

OBJECTIVE: to evaluate the effect of the addition of low dose human chorionic gonadotropin (hCG) to human menopausal gonadotropin (HMG) throughout the early follicular phase in controlled ovarian stimulation (COS) conducted with two difference regimens. Gonadotropin-releasing hormone (GnRH) antagonist and short GnRH-agonist protocol were applied in two in vitro fertilization (IVF) clinics. METHODS: Clinical study conducted during the period 2014-2016 in two IVF clinics in a cohort of 240 women. In the first group 1 (124 women), a GnRH antagonist protocol with HMG and addition of low dose (100IU/day) h CG was applied. The other group 2 consisted of 116 women who underwent a short GnRH- agonist protocol with HMG and addition of low dose (100IU/day) h CG. RESULTS: Multiple logistic regression analysis was performed. The group 2 found to be associated with greater number of follicles and oocytes. The pregnancy rates were 12.1% and 26.7% in group 1 and group 2, respectively (p=0.004). For patients over 40 years, the number of follicles and oocytes retrieved were significant higher in group 2.The pregnancy rate in group 2 was higher than in group 1 (21, 6% vs 5%, p=0.017). CONCLUSIONS: Advanced age women are likely to achievepregnancy using the GnRH Short than GnRH antagonist, when HMG/hCG is used, while HMG-hCG gonadotropins have the same potentialas Recombinant follicle stimulating hormone (rFSH)-hCG used in GnRH short protocol.

Daily administration of a GnRH analogue enhances sperm quality in bucks during the non-breeding season.

The aim of this study was to determine if daily administration of a GnRH analogue (buserelin acetate) to bucks during the non-breeding season increases testosterone concentration and improves sperm quality. Five bucks received a daily dose of buserelin for 10 days, starting on Day 0 (first administration), and another five bucks remained as controls. Testosterone concentrations were greater in treated than in control bucks during the first hours after buserelin administration (P = 0.05), but greater in controls 10 h later (P < 0.01). Sperm mass motility and percentage of motile sperm were greater in treated (3.9 ± 0.6 and 70.1 ± 7.9%, respectively) than in control bucks (1.0 ± 0.6, P < 0.01; 45.0 ± 7.9%, P < 0.05 respectively) on Day 4. Percentage of sperm with normal morphology tended to be greater in treated than in control bucks (81.8 ± 6.2% compared with 63.5 ± 6.4% respectively, P = 0.08). The treatment decreased the percentage of sperm with mid piece defect and with bent tail (7.0 ± 1.5% compared with 12.0 ± 1.5%; 8.0 ± 1.7% compared with 13.5 ± 1.7%, treated and control bucks, respectively, P = 0.05 for both). The square root percentage of sperm with loose but heads with normal structures tended to be less in treated than control bucks (1.3 ± 0.3% compared with 0.4 ± 0.3% respectively, P = 0.06). It was concluded that daily administration of buserelin during the non-breeding season led to a rapid increase in testosterone concentration and improved sperm quality.

Profile of LH release in response to intramuscular treatment with kisspeptin in Bos indicus and Bos taurus prepubertal heifers.

The main objective of this study was to evaluate the effect of intramuscular (I.M.) administration of different doses of kisspeptin (Kp) on the pattern of luteinizing hormone (LH) release in Bos taurus and Bos indicus prepubertal heifers. Holstein heifers weighing 215.1 ±â€¯38.6 kg (n = 24; aged 5-8 mo) and Gyr heifers weighing 215.4 ±â€¯31.4 kg (n = 24; aged 6-10 mo) were enrolled in this study. The animals were confirmed as non-cyclical by absence of a corpus luteum (CL) as determined by ultrasound scanning of the ovaries and low circulating P4 concentrations (<1.0 ng/mL) evaluated at a 10-day interval (on day -10 and day 0). For each genetic group, heifers were randomly assigned to one of four treatments: Kp at 2.5 µg/kg body weight (Kp2.5), Kp at 5.0 µg/kg (Kp5), Kp at 10 µg/kg (Kp10), or gonadotropin-releasing hormone (GnRH) agonist (0.01 mg of buserelin acetate per heifer), all administered by I.M. injection. All animals responded to the treatments with an LH surge (P < 0.01). There was an effect of breed (P < 0.01) on induced LH release, with Holstein heifers having a greater area under the curve for LH (AUC; P < 0.01) and greater LH peak amplitude (P < 0.01) than Gyr heifers. Nevertheless, greater AUC for LH occurred in Kp10 heifers for both breeds. There was no effect of breed on LH AUC or LH peak amplitude after GnRH agonist treatment. For both breeds, heifers treated with Kp displayed an earlier (P < 0.01) LH peak with a reduced amplitude of the LH peak (P < 0.01) and reduced LH AUC (P < 0.01) compared to heifers treated with GnRH agonist. Thus, both zebu and taurus immature heifers treated with I.M. Kp injection responded with a rapid and dose-dependent LH surge, although even large doses of the native Kp-10 did not mimic the magnitude or duration of the LH surge produced by the GnRH agonist. The early onset of the LH surge after Kp treatment and the short duration suggest that the effects of Kp were likely due to pituitary rather than hypothalamic action. Finally, there seems to be a greater responsiveness to Kp in Bos taurus than in Bos indicus prepubertal heifers, although LH release after GnRH agonist treatment was similar for the two breeds.

Protection of GnRH analogue by chitosan-dextran sulfate nanoparticles for intravaginal application in rabbit artificial insemination.

The present study was designed to prove new rabbit insemination extenders containing aminopeptidase inhibitors (AMIs) with or without chitosan (CS)-dextran sulfate (DS) nanoparticles entrapping the GnRH analogue. In addition, different hormone concentrations were tested in these extenders, evaluating their in vivo effect on rabbit reproductive performance after artificial insemination. A total of 911 females were inseminated with semen diluted with the four experimental extenders (C4 group: 4 µg buserelin/doe in control medium (Tris-citric acid-glucose supplemented with bestatin 10 µM and EDTA 20 mM), C5 group: 5 µg of buserelin/doe in control medium, Q4 group: 4 µg of buserelin/doe into CS-DS nanoparticles in control medium, Q5 group: 5 µg of busereline/doe into CS-DS nanoparticles in control medium). Results showed that fertility was significantly lower in C4 group compared to C5, Q5 and Q4 groups (0.7 versus 0.85, 0.85 and 0.82, respectively). On the contrary, prolificacy was similar in the four experimental groups studied (P > 0.05). We conclude that the CS-DS nanoparticles prepared by a coacervation process as carrier for buserelin acetate allows reducing the concentration of hormone used in extenders supplemented with bestatin and EDTA without affecting the fertility and prolificacy of rabbit females.

Synchronization of time of ovarian follicular development in llamas (Lama glama) using a protocol based on GnRH and PGF2α.

The aim of this study was to evaluate the effectiveness of a protocol based on GnRH and PGF2α to synchronize the emergence of a new wave of ovarian follicular development in llamas and, therefore, when a new dominant follicle develops. Llamas (n = 18) were assigned to growing, mature or regressing follicle groups according to the phase of the follicular wave at the beginning of treatment. The protocol was initiated with a GnRH analogue (GnRHa) injection on Day 0 followed 7 days later with a d-cloprostenol injection and a second GnRHa injection on Day 10. Ovulation rate after the first GnRHa treatment, day of new follicle emergence, mean plasma progesterone concentration and percentage of animals with a newly developed dominant follicle ≥ 7 mm on Day 10 were evaluated. Ovulation rate after the first GnRHa was less in the regressing than mature and growing follicle groups and new follicular wave emergence occurred earlier in the regressing follicle group than in the other two groups. Mean plasma progesterone concentration in females that had ovulations after the first GnRHa injection was similar. The percentage of animals that had a new follicle ≥ 7 mm on Day 10 was not different among groups and the overall percentage was 66.6%. The total synchronization rate for development of a new wave of follicular development on Day 10 was greater in females having ovulations after the first GnRHa injection than in those that did not have ovulations. In conclusion, the protocol used in the present study was useful for synchronizing ovarian follicular development in 66% of the llamas regardless of the phase of the follicular wave development at the beginning of treatment.

Effect of consecutive re-synchronization protocols on pregnancy rate in buffalo (Bubalus bubalis) heifers out of the breeding season.

The combined effect of six consecutive timed artificial inseminations (TAIs) on pregnancy rates, following two different synchronization protocols on buffalo heifers, over a period of seven months typically characterized by low breeding performances, were investigated in this study. A total of 2189 TAIs were performed on 1463 buffalo heifers within a large buffalo farm in the south of Italy. Individual animals were allowed to undergo synchronization protocol (either a slightly modified Ovsynch or Progesterone treatment) and TAI until establishment of pregnancy or else for not more than six consecutive times. Semen of seven proven bulls was used throughout the study, which was carried out from March to September of the same year. Therefore, other than the effect given by consecutive TAIs over time, a monthly and a seasonal effect could also be tested, once the entire period was split into a Low Breeding Season (LBS) from March to June, and a Transition to Breeding Season (TBS) from July to September. From the data recorded in this study and the statistical analysis performed, it can be stated that the two protocols for the synchronization of ovulation were similar in efficiency in determining pregnancies with an overall fertility rate of 89.4% when the comparison was run both on a monthly basis or when months were grouped into two different seasons. In addition, an average of 1.83 AI/pregnancy was reported, slightly higher for the Ovsynch when compared to the Progesterone protocol: 1.91 vs 1.70, respectively. Finally, when considering the number of progressive synchronization treatments implemented over time as covariate, neither Ovsynch nor Progesterone treatment significantly affected pregnancy rates following the first of the six synchronization sessions. However, repeating the synchronization procedure, the progesterone based protocol resulted in significantly higher probability of success in terms of established pregnancies during the second and third re-synchronization sessions.

Establishing an Animal Model of Secondary Osteoporosis by Using a Gonadotropin-releasing Hormone Agonist.

Introduction: Orchidectomy is currently the preferred method to induce bone loss in preclinical male osteoporosis model. Gonadotropin-releasing hormone (GnRH) agonists used in prostate cancer treatment can induce testosterone deficiency but its effects on bone in preclinical male osteoporosis model are less studied. Objective: This study aimed to evaluate the skeletal effect of buserelin (a GnRH agonist) in male rats and compare it with orchidectomy. Methods: Forty-six three-month-old male Sprague-Dawley rats were divided into three experimental arms. The baseline arm (n=6) was sacrificed at the onset of the study. In the buserelin arm, the rats received a daily subcutaneous injection of either normal saline (n=8), buserelin acetate at 25 µg/kg (n=8) or 75 µg/kg (n=8). In the orchidectomy arm, the rats were either sham-operated (n=8) or orchidectomized (n=8). All groups underwent in-vivo X-ray micro-computed tomography scanning at the left proximal tibia every month. Blood was collected at the beginning and the end of the study for testosterone level evaluation. The rats were euthanized after the three-month treatment. The femurs were harvested for biomechanical strength and bone calcium determination. Results: The results showed that buserelin at both doses caused a significant decline in testosterone level and deterioration in bone microstructure (p<0.05), but did not affect bone calcium content (p>0.05). Buserelin at 25 µg/kg decreased displacement and strain of the femur significantly (p<0.05). Similar changes were observed in the orchidectomized group compared to the sham-operated group but without any significant changes in biomechanical strength (p>0.05). Conclusion: Buserelin can induce testosterone deficiency and the associated deterioration of bone microarchitecture similar to orchidectomy in three months. However, it may require a longer time to show significant effects on bone strength and mineral content.

Pregnancy rate in water buffalo following fixed-time artificial insemination using new or used intravaginal devices with two progesterone concentrations.

This study evaluated the pregnancy rate (PR) after timed artificial insemination (TAI) in water buffalo (Bubalus bubalis) during both non-breeding and breeding season, using either a new or reused intravaginal device (IVD) with two different progesterone concentrations. A total of 247 dairy buffalo cows were randomly assigned using a two-by-three factorial design and four replicates to the following groups: (1) new intravaginal device (IVD-New: DIB®, 1.0 g of P4, n = 51 or CIDR®, 1.38 g of P4, n = 55); (2) intravaginal device previously used once (9 days) (IVD-Used1x: DIB, n = 40 or CIDR, n = 51); or (3) intravaginal device previously used twice (18 days) (IVD-Used2x: DIB, n = 27 or CIDR, n = 23). On day 0, animals received the IVD plus 10.5 µg of buserelin acetate (GnRH) intramuscularly. On day 9, the devices were removed and 25 mg of PGF2α plus 500 IU of eCG was given intramuscularly. On day 11 (48 h after IVD withdrawal), animals received 10.5 µg of GnRH and were artificially inseminated 8-12 h later. Data were analyzed using Proc Logistic of SAS®. Animals that received IVD-New-DIB, had a significantly higher PR (62.7%; P = 0.0193) compared to animals that received IVD-New-CIDR (40%). Pregnancy rate was not negatively affected by reusing both types of IVD. Overall PR (new and reused devices) was higher (P = 0.0055) in the DIB group (62.7%) compared to the CIDR group (45%). In conclusion, PR was higher in buffaloes treated with devices containing 1.0 g of P4 (DIB®) compared to those receiving 1.38 g of P4 (CIDR®). Reusing the intravaginal devices did not affect negatively PR/TAI, suggesting that P4 concentrations within the TAI protocols in water buffaloes could be reduced, without impairing their fertility.

Corpus luteum dynamics after ovulation induction with or without previous exposure to progesterone in prepubertal Nellore heifers.

The objectives of this study were 1) to monitor corpus luteum (CL) dynamics after two different protocols of ovulation induction in prepubertal Nellore heifers, and 2) to determine differences in luteal function. Fifty-seven heifers (weight 289.61 ± 32.28 kg, BCS 5.66 ± 0.65, age 17.47 ± 0.81 months) were divided into two groups: GP4+GnRH received a progesterone (P4) device of 3rd use for 10 days, followed by the administration of 0.02 mg buserelin acetate (GnRH) 48 h after removal of the device, and GGnRH received only GnRH. The CLs formed were monitored by ultrasonography every 2 days until their functional regression (decrease in the color Doppler signal and serum P4 concentration < 1 ng/mL), determining their diameter and area, numerical pixel value (NPV), pixel heterogeneity, and vascularization percentage. The peak systolic velocity, end diastolic velocity, resistivity index and pulsatility index (PI) of the ovarian artery and serum P4 concentration were also measured. A lifespan of the CL of more than 16 days was classified as normal-function and of less than 16 days as premature regression. The variables were compared between treatments, CL categories (normal-functional, prematurely regressed or non-functional), days of evaluation, and their interactions using the MIXED procedure of the SAS program (p ≤ 0.05). Three animals of each group (6/57 = 11%) did not respond to treatment, corresponding to an ovulation rate of 89%. There was a higher percentage of normal-function CLs in GP4+GnRH (81%) and a higher percentage of non-functional CLs in GGnRH (52%; P4 concentration < 1 ng/mL in all assessments). Normal-function CLs exhibited a greater area, vascularization percentage and P4 concentration than prematurely regressed and non-functional CLs. Lower diameter, area, NPV and P4 concentration were observed for non-functional CLs, but there was no difference in vascularization percentage compared to prematurely regressed CLs. Progesterone concentration was efficient in diagnosing CL function and was positively correlated with CL area (r = 0.62; p < 0.001) and vascularization percentage (r = 0.38; p < 0.001). Diameter and PI were important for the early diagnosis of non-functional and prematurely regressed CLs, respectively. In conclusion, luteal function differed for the first CL that develops after ovulation induction in prepubertal heifers. Ultrasonographic parameters (diameter, area, NPV, vascularization percentage, and PI) can be used to predict CL function.