Chronic use of a GnRH agonist (deslorelin) or immunization against GnRH: effects on testicular function and sperm quality of bucks

Immunocontraception of male domestic cats using GnRH vaccine Improvac

The domestic cat is a highly prolific species; thus, reproductive control is crucial to reducing feral cat overpopulation. This study aimed to assess the effect of a commercially-available GnRH vaccine for swine on suppressing sperm production in male cats. Twelve sexually mature tomcats were randomly divided into two groups. Treated cats (n = 9) received a GnRH vaccine (Improvac, Zoetis Belgium SA, 0.5 mL sc) twice 4 wk apart, and the control group (CON, n = 3) saline solution (0.5 mL sc). Reproductive parameters and blood samples were recorded every 2 wk, from 6 wk before vaccination until 24 wk after the first dose. Day 0 of the study was defined as the day of primary immunization with either the vaccine or saline solution. Serum testosterone concentrations of treated cats dropped to basal levels 6 wk after D0, while CON cats maintained serum testosterone concentrations between normal ranges during the study period. No differences were observed in pretreatment and CON seminal samples. However, a progressive decrease in seminal quality was observed in treated cats from wk 8 until the end of the study. By wk 24, sperm concentration and total sperm count decreased by 90%, motility decreased by 70%, and viability decreased by 60%. Moreover, testicular volume was reduced by 49%, and penile spines showed almost complete atrophy by the end of the study. Although treated cats showed a decrease in the hematocrit, erythrocyte count, and hemoglobin concentration, values were within the reference range for domestic cats. No differences were observed in the other hematological and biochemical parameters evaluated. Our results agree with previous immunocontraception studies in cats, showing that Improvac vaccination effectively reduced sperm quality, testicular volume, and serum testosterone concentration. Further studies should be carried out to define the Improvac long-term effect.

Single or repeated immunization against GnRH fails to completely abolish spermatogenesis in dwarf bucks (Capra hircus)

In both captive wildlife and production animals is important to develop strategies for population control. Immunization against GnRH is an easy and inexpensive immunocastration method that reduces the concentration of testosterone and decreases sperm quality. However, its effectiveness depends on the species and repetition of the treatment. This study aimed to compare the effectiveness of a single treatment (initial immunization plus a booster with Improvac) vs repeated treatment (six doses of Improvac) to inhibit testicular function and maintain the contraceptive status during long periods in bucks. Three Dwarf bucks (Capra hircus) received two doses of Improvac, the first on Week 0, and the booster 4 weeks later (single immunization, group SI) while three Dwarf bucks received one dose of Improvac every 6 months during 3 consecutive years (repeated immunization, group RI). The other three Dwarf bucks remained untreated (control bucks, group CON). Bucks from RI had a greater decrease in scrotal circumference, testosterone concentration, male odor intensity, and sperm quality than SI bucks. However, there were no differences between SI and CON bucks in any of the variables studied. Overall, repeated treatment of Improvac decreased the testicular function of Dwarf bucks, although did not produce complete infertility. However, the repetition of the treatment produced more intensive negative effects, indicating that the strength of the effects of Improvac is rapidly lost in bucks.

The High Testosterone Concentrations of the Bucks Used in the "Male Effect" Is Not a Prerequisite for Obtaining High Ovarian Activity in Goats from Mediterranean Latitudes

Two experiments were carried out. Firstly, 54 anestrous females were placed in contact with photostimulated males (Photo; n = 27) or with no photostimulated males (Natural; n = 27). Moreover, a group of bucks treated with artificial photoperiod and a group of bucks subjected to natural photoperiod without contact with females was used (Photo Isolated and Natural Isolated, respectively). In the Natural groups, the testosterone concentrations were similar except for three days after the introduction of the bucks to the does (19.72 ± 4.11 vs. 2.05 ± 0.25 ng/mL for Natural and Natural isolated bucks, respectively, p < 0.05). However, no differences were observed in the Photo groups during the entire experiment. The percentage of females showing estrous was higher in the group of females in contact with photostimulated bucks (96 vs. 74%, respectively, p < 0.05). In the second experiment, a GnRH agonist, deslorelin, was used to regulate the testosterone concentrations of the bucks. Seventy anestrous females were divided into five groups depending on the treatment received by the bucks to which they were exposed: photostimulated bucks (Photo group, n = 14); photostimulated bucks but treated with the agonist at the onset of the photoperiod treatment (Photo-Ago Long group, n = 13); photostimulated bucks but treated with the agonist at the end of the photoperiod treatment (Photo-Ago Short group, n = 15); bucks receiving no photostimulation but treated with the agonist at the end of the photoperiod treatment period (Natural-Ago Short group, n = 13) and bucks receiving no photostimulation nor agonist (Natural group, n = 15). The agonist treatment increased testosterone concentrations after the injection, which remained high for the entire experiment (p < 0.05). Six days after the introduction of the bucks to the does, the testosterone concentrations increased only in the Natural group reaching similar concentrations to the other groups (12.17 ± 6.55, 16.69 ± 4.53, 8.70 ± 0.61, 11.03 ± 1.45 and 14.42 ± 3.64 ng/mL for Photo, Photo-Ago Long, Photo-Ago Short, Natural-Ago Short and Natural bucks, respectively, p > 0.05). No differences in reproductive parameters were observed (p > 0.05). These results demonstrate that, at Mediterranean latitudes, anestrous females can stimulate the testosterone concentrations of bucks after a period of isolation. The high testosterone concentrations are not a prerequisite for an adequate response to the male effect.

Semen quality, testosterone values, and testicular and accessory gland parameters in rams receiving sustained stimulation with low doses of buserelin

ContextThe use of buserelin, a gonadotropin-releasing hormone (GnRH) agonist, can improve semen quality. Nevertheless, the appropriate dosage, and frequency and time of application, remain to be established owing to the subsequent negative feedback on endogenous production of testosterone described so far.AimsThis study aimed to propose a new buserelin application protocol for sperm improvement in Santa Inês rams.MethodsFifteen Santa Inês rams were divided into two experimental groups: the first group (n=8) received 2.5μg buserelin acetate; and the second group (n=7) received saline solution. Treatments were applied for 21 days at intervals of 6h, totalling four hormonal or saline applications per day. In all animals, macroscopic and microscopic seminal characteristics and freezability, plasma testosterone, pixels of testicular parenchyma, and biometric analysis of testicular and accessory sex glands by ultrasound were evaluated throughout the period of hormonal application and for a further 7 days.Key resultsRams receiving buserelin showed a peak of testosterone after the first week (Day 7) of application, with a drop in values at Day 14, followed by negative feedback at Day 21 and return to basal concentrations at Day 28. They also showed improvement of kinetics parameters such as straight line velocity (μm/s: +buserelin 51.5±1.5 &gt; control 46.6±1.6) and linearity coefficient (%: +buserelin 53.5±1.8 &gt; control 47.5±1.9). Ultrasound parameters, pixels of testicular parenchyma, and freezability were not affected by treatment.ConclusionsThe administration of buserelin was able to improve some sperm kinetics parameters of Santa Inês rams.ImplicationsLow doses of this GnRH analogue can be used; however, further adjustments to the hormonal protocol are needed to obtain an effective improvement in sperm quality.

Endocrine aberrations of human nonobstructive azoospermia

Nonobstructive azoospermia (NOA) refers to the failure of spermatogenesis, which affects approximately 1% of the male population and contributes to 10% of male infertility. NOA has an underlying basis of endocrine imbalances since proper human spermatogenesis relies on complex regulation and cooperation of multiple hormones. A better understanding of subtle hormonal disturbances in NOA would help design and improve hormone therapies with reduced risk in human fertility clinics. The purpose of this review is to summarize the research on the endocrinological aspects of NOA, especially the hormones involved in hypothalamic–pituitary–testis axis (HPTA), including gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, testosterone, estradiol, sex hormone binding globulin, inhibin B, anti-Müllerian hormone, and leptin. For the NOA men associated with primary testicular failure, the quality of currently available evidence has not been sufficient enough to recommend any general hormone optimization therapy. Some other NOA patients, especially those with hypogonadotropic hypogonadism, could be treated with hormonal replacement. Although these approaches have succeeded in resuming the fertility in many NOA patients, the prudent strategies should be applied in individuals according to specific NOA etiology by balancing fertility benefits and potential risks. This review also discusses how NOA can be induced by immunization against hormones.

Response of rams to electroejaculation following the administration of oxytocin and cloprostenol with or without GnRH

The present study aims to evaluate the effect of administering prostaglandin (250 μg cloprostenol) and oxytocin (10 UI) or a GnRH agonist (4.2 μg buserelin acetate) on rams' physiological responses to electroejaculation and the ejaculate's characteristics. The study was performed with a 2 × 2 factorial arrangement, according to whether it used oxytocin and prostaglandin (OXPGF) or GnRH. Therefore, there were four treatments: GControl = saline; GOXPGF = administration of PGF2α and oxytocin; GGnRH = administration of GnRH; administration of GOXPGF + GnRH = GnRH and PGF2α + oxytocin. An interaction between the hormonal treatments in the heart rate occurred: while the heart rate decreased when using OXPGF alone (control: 113.7 bpm vs. GOXPGF: 103.5 bpm, pooled SEM; P = 0.02), it did not modify when applying both treatments simultaneously and administering GnRH (GGnRH: 109.1 bpm vs. GOXPGF + GnRH: 111.5 bpm respectively, pooled SEM = 4.5). The respiratory rate also decreased with the administration of OXPGF (38.7 vs. 46.3 with and without OXPGF, pooled SEM = 10.0, P = 0.003). Administering OXPGF also tended to decrease the temperature (38.77 °C vs. 38.94 °C, with and without OXPGF, respectively, pooled SEM = 0.06; P = 0.056). Blood glucose increased with the administration of OXPGF from 58.7 mg/dL to 62.4 mg/dL (pooled SEM = 1.3, P = 0.014) and varied with time. CK concentrations increased from 641.8 mg/dL to 881.7 mg/dL (pooled SEM = 50.6) with the administration of OXPGF. GnRH administration decreased cortisol concentration from 7.3 ng/mL to 2.1 ng/mL (pooled SEM = 1.4; P = 0.04). The treatments had no effects on the time required for EE, the pulse at which the animals began and ended the ejaculation, or the vocalizations emitted during EE. There were no effects in any evaluated sperm variable. The research concluded that the administration of oxytocin and analogs of PGF2alpha decreased the stress response to electroejaculation, as well as administering GnRH agonist was slightly effective as it only decreased cortisol concentration. Also, these treatments, either alone or combined, did not affect the characteristics of the ejaculate collected.

Detection of Local Tissue Reactions after Anti-GnRF Injection in Male Pigs Assessed Using Magnetic Resonance Imaging

Simple Summary

Local tissue reactions after injection are known in animals and humans. This study analysed the local tissue reaction after injection of the so-called immunologic castration in pigs using magnetic resonance imaging to achieve insight into the reaction site. Long-lasting reactions, which can be traced to inflammatory reactions, were detected. Further studies are needed to evaluate the impact of these reactions on animal well-being and carcass quality.

Abstract

This study aimed at evaluating the local tissue reaction of an anti-GnRF product, which is used for the so called “immunocastration” in male pigs. A total of 34 pigs were injected two times (including a booster injection) with an anti-GnRF product. Injection was performed using the prescribed safety vaccinator. Injection sites were evaluated three times post injection using magnetic resonance imaging. Two examinations were performed after the first injection and one after the booster. The local tissue reaction was evaluated three-dimensionally by semi-automatic analyses, by linear measurements of injection depth and length, and by scoring the kind of tissue affected. Results showed a long-lasting reaction in affected muscle tissue. Therefore, needle length should be discussed, and an evaluation of the injection site after slaughter should be performed include behavioural scorings post injection to evaluate the impact on animal well-being and carcass quality.

Seasonality of the stress response in goat bucks when there is use of electroejaculation for semen collection

Electroejaculation (EE) is frequently used to collect semen, but this procedure is both stressful and painful. In seasonal-breeding species the sensitivity to stressors might vary with season of the year when semen collection occurs, therefore, the present study was conducted to compare the responses when imposing the EE procedure, stress response to EE and fresh semen characteristics in goat bucks throughout the year. Semen was collected using EE from goat bucks once in autumn (mid-breeding season), winter (transition to the non-breeding season), spring (non-breeding season), and summer (beginning of the breeding season). The number of pulses applied during ejaculation was larger in the autumn and spring than winter and summer months. The number of vocalizations/pulse while bucks were ejaculating was greater in the summer than winter and spring months. The increase in heart rate was greater in spring than summer months. Cortisol concentration was least in the autumn, and concentration of creatine kinase (CK) was greatest in summer. Sperm mass motility was greater in autumn than spring months. Spermatozoa concentration, total number of spermatozoa ejaculated, motile spermatozoa ejaculated, and progressively motile spermatozoa were greater in the autumn and spring than in the winter and summer months. The bucks were less stressed by imposing EE procedures in the autumn, and buck responses were greater in the spring-summer period. Bucks had a greater incremental increase in serum CK and number of vocalizations in the summer months, indicating there was a greater muscular damage and quite likely pain associated with lesser semen quality.