Applications of GnRH in the control and management of fertility in female animals

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.

Ameliorative effects of aerobic training in girls with precocious puberty: role of leptin and ghrelin

This study was an attempt to examine the changes in serum levels of ghrelin and leptin after 12-weeks of aerobic training and gonadotropin releasing hormone agonist (GnRH) treatment in girls with central precocious puberty. Thirty girls (6-8 years old) with precocious puberty who had received Triptorelin were randomly divided in two groups (medication and medication + training). Fifteen age-matched healthy girls (without precocious puberty) were also included as the control group. The medication + training group submitted an aerobic training program for 3 days/week with 20-75 min per day and 45-75% of maximum heart rate for 12-weeks. Serum levels of leptin, ghrelin, cholesterol, triglycerides and body mass index (BMI) were determined at baseline and 48 h after the last training session. The results indicated that leptin significantly decreased (p = 0.001) and ghrelin significantly increased (p = 0.001) in the medication + training group but no significant difference was observed in the ghrelin (p = 1) and leptin (p = 0.78) in the medication group. Leptin to ghrelin ratio indicated a decrease in medicine + training group (p = 0.028). Ghrelin were negatively correlated with leptin and BMI. The data indicated that aerobic training increased ghrelin and reduced leptin and leptin to ghrelin ratio but GnRH agonist treatment had no effect on plasma leptin and ghrelin levels.

Effect of GnRH agonist (deslorelin) on reproductive activity in captive female veiled chameleons (Chamaeleo calyptratus)

Eighteen 5 months old veiled chameleon females (Chamaeleo calyptratus) were used in the study. Seven females received subcutaneous implants with gonadotropin-releasing hormone agonist (GnRH) deslorelin acetate whereas eleven females were used as control animals without any implants. Females were kept in five terraria, in groups of four females (in 3 terraria) and groups of three females (in 2 terraria), respectively. A minimum of one female with GnRH implants was present in each terrarium. They were kept under standard husbandry conditions. Females of both groups (females with GnRH and controls, respectively) were monitored for three years. No differences between females with GnRH implants and females without GnRH implants were observed with respect to the presence of large ovarian follicles, number of eggs/female, or number of clutches/female. GnRH implants did not prevent spontaneous reproductive activity in any of the 7 females with implants. Ovariectomy was performed in 8 females (4 females with GnRH implants and 4 control females). Ten females (3 females with GnRH implants and 7 control females) had to be euthanised. In 17 of 18 female veiled chameleons of this study histologic examination revealed heterophilic granulomatous oophoritis. The use of GnRH agonist implants did not prove to be an appropriate method for the control of reproductive function in captive female veiled chameleons.

Effects of water-soluble additive on the release profile and pharmacodynamics of triptorelin loaded in PLGA microspheres

A satisfactory drug release profile for gonadotropin-releasing hormone (GnRH) agonist drugs is high initial release followed by small amount of drug release per day. In the present study, three water-soluble additives (NaCl, CaCl₂ and glucose) were selected to improve the drug release profile of a model GnRH agonist drug-triptorelin from PLGA microspheres. The pore manufacturing efficiency of the three additives was similar. The effects of three additives on drug release were evaluated. Under the optimal initial porosity, the initial release amount of microspheres containing different additives was comparable, this ensured a good inhibitory effect on testosterone secretion in the early stage. For NaCl or CaCl₂ containing microspheres, the drug remaining in the microsphere depleted rapidly after the initial release. The testosterone concentration gradually returned to an uncontrolled level. However, for glucose containing microspheres, it was found that the addition of glucose could not only increase the initial release of the drug but also assist in the subsequent controlled drug release. A good and long-time inhibitory effect on testosterone secretion was observed in this formulation. The underlying cause why the incorporation of glucose delayed the subsequent drug release was investigated. SEM results showed that considerable pores in glucose containing microspheres were healed during the microspheres incubation. After thermal analysis, an obvious glass transition temperature (Tg) depression was observed in this formulation. As Tg decreased, polymer chains are able to rearrange at lower temperatures. This, morphologic change was reflected in the gradual closure of the pores, and is the likely reason that drug release slowed down after the initial release.HighlightsThe addition of glucose could not only increase the burst release of the drug but also delay the subsequent drug release.High initial burst and a sustained drug release helped obtain a good inhibitory effect on testosterone secretion.As Tg decreased, polymer chain was prone to rearrange. Morphologic change was reflected in the gradual closure of the pores. This was the reason that drug release slowed down after the initial burst.

Efficacy and Safety of 4.7 mg Deslorelin Acetate Implants in Suppressing Oestrus Cycle in Prepubertal Female Dogs

Our multicentric, masked, controlled and randomised study aimed to assess the efficacy and safety of Suprelorin® 4.7 mg (Virbac, Carros, France) regarding oestrus prevention in prepubertal intact bitches. Twelve- to eighteen-week-old females (n = 83) were allocated either a deslorelin implant (n = 62) or 0.9% sodium chloride (n = 21) group. Clinical assessment (heat signs), 17β oestradiol and progesterone assays, and vaginal cytology were performed at day (D)0, D7, D21, month (M)3 and M6 after product administration, and were then performed every other month until reaching puberty. Trained owners assessed heat signs between each veterinary visit. All bitches (n = 83) reached puberty before M30. Deslorelin significantly extended the median time to sexual maturity when compared to the control group (377 days versus 217 days after D0, p < 0.0001). Three females, implanted between 16 and 18 weeks of age, expressed an induced oestrus. Additional descriptive data, collected over a 24 month-period, showed functional reproductive abilities in both deslorelin (n = 52) and control (n = 21) groups once puberty was achieved. In conclusion, Suprelorin® 4.7 mg seems to be an effective and safe option for postponing the onset of oestrus when administered to prepubertal female dogs aged from 12 to 16 weeks.

Artificial Insemination in Queens in the Clinical Practice Setting: Protocols and challenges

PRACTICAL RELEVANCE

Despite substantial advances in assisted reproductive techniques having been recently reported in cats, the use of these is limited and routine application is still far from being a reality in veterinary clinics. Nevertheless, there is an increasing demand from domestic cat breeders for artificial insemination (AI) techniques that are already commonly used in dogs. Where natural breeding is not possible in tom cats and queens of high breeding value, AI could offer a solution. Clinical challenges: AI in cats is more difficult than in other species - both in terms of semen collection/handling and oestrous cycle management given that ovulation must be induced.

AIM

For practitioners wishing to perform AI in queens, there are challenges to overcome, and a good understanding of the techniques and procedures involved is pivotal. This review aims to contribute to improved knowledge by providing an overview of AI protocols, encompassing choice of breeding animals, procedures for semen collection, oestrus and ovulation induction, AI techniques and equipment.

EQUIPMENT AND TECHNICAL SKILLS

Depending on the animals involved and the specific AI technique chosen, essential equipment may include an artificial vagina, electroejaculator, endoscope (sialendoscope, which can be fairly expensive) and special catheters for transcervical insemination. Other instrumentation and materials needed are typically readily available in a veterinary clinic. In general, no particular skills are needed to perform the procedures described in this review, with the exception of endoscopic transcervical catheterisation, where the ability to use an endoscope is required.

EVIDENCE BASE

The information and advice/recommendations provided are based on specific feline research and reviews published in scientific peer-reviewed journals, animal reproduction textbooks, and presentations at national and international congresses. The authors also drew on their own clinical experience with regard to the choice of protocols and procedures presented in this review.

Wound Retractor Laparoscopic Port System for Laparoscopic Ovariectomy in Panthera leo

The aim of this study was to assess the feasibility and intraoperative complications of performing ovariectomies in African lionesses (Panthera leo) using a wound retractor laparoscopic platform. Six lionesses (n = 6) were included. The surgical procedures were carried out through three portals, with a retractor platform positioned at the umbilical port and cannulas placed 3–4 cm from the cranial and caudal regions to the device at the level of the midline. An ovariectomy was performed with a vessel-sealing device. We evaluated the surgery time and the intraoperative and early postoperative complications. The mean weight was 172.83 kg. The total surgery time was 49.33 min. The installation step took a mean of 10.33 min to complete. The mean ovariectomy time was 20 min. Controlled bleeding was observed at the tip of the uterine horn in two cases due to excessive tissue thickness. The retrieval of dissected ovarian tissue and annexes was easily performed. No other complications were observed. The use of the laparoscopic platform during three-portal surgeries for laparoscopic ovariectomy in adult overweight lionesses is feasible and without intraoperative problems. The retractor meant that there were no entry-related issues due to the 25 mm mini-laparotomy. It also made it simpler to extract thick ovaries and promptly re-establish the pneumoperitoneum.

Double-Blind, Placebo-Controlled Trial of Cyproterone Acetate to Prevent Flare-Up Effect on Dogs Implanted With Deslorelin

Deslorelin slow-released implants are registered in Europe for the reversible suppression of fertility in male dogs. After administration, a time-limited increase in sex hormones concentration and related behavioral problems may be observed. The aim of this work was to assess whether cyproterone acetate, a synthetic progestogen, can prevent this flare-up effect. Eighteen privately-owned entire male dogs were enrolled in this double-blind, placebo-controlled, randomized clinical trial. All subjects received a 4.7 mg deslorelin implant by SC route and 1-3 capsules containing either cyproterone acetate 2 mg/kg (N = 9) or a placebo (N = 9), by oral route BID for 14 days, depending on the dog's weight. The dogs were followed for 28 days. An increase in the blood testosterone concentration was observed in respectively 9/9 and 7/9 dogs of the control and cyproterone groups (p = 0.47). However, a worsening of the sex hormone related problems (i.e., urinary marking, mounting, aggressiveness toward other dogs and/or escape) was only observed in the placebo group, in 56 or 66% of the dogs as measured by respectively the veterinarian and the owners. Our study suggests that cyproterone acetate is effective and safe to supress the deslorelin induced behavioral flare-up effect, but not the rise in testosterone.

Resumption of ovarian activity following removal of a 4.7 mg deslorelin implant in queens

Deslorelin implants are widely used in felines. Due to their prolonged duration cat breeders frequently request early implant removal. The interval between deslorelin implant removal and resumption of ovarian function in queens is unknown. The aim of this study was to evaluate the interval between the removal of a deslorelin implant and the resumption of ovarian activity in adult queens. Twenty-three queens were treated with a 4.7 mg deslorelin implant placed in the periumbilical area. In the 16 queens completing the study implants were surgically removed at 3, 6 or 9 months (n = 6, 4 and 6 queens, respectively). Queens received a GnRH stimulation test as part of their pre-treatment general and reproductive health check. Following implantation treatment, all queens in inter-oestrus-anoestrus at the time of treatment came in oestrus within 2-5 days. Starting 7-14 days following implant removal queens were checked every 1-2 weeks with reproductive ultrasonography, a vaginal smear and blood collection. The interval to resumption of ovarian function ranged from 3 to 7 weeks irrespective of treatment length and age of the queen but was longer when the implant was removed at decreasing photoperiod (p < .05). In conclusion, at least 3 weeks post-removal are needed during increasing photoperiod to achieve follicular development and oestrogen production sufficient to support oestrous behaviour in queens following removal of a 4.7 mg deslorelin implant, while this time may increase up to 7 weeks during decreasing photoperiod. Further studies are needed to assess the interval between removal of a deslorelin implant and occurrence of ovulation as well as fertility at the first oestrus after a deslorelin treatment.

The status of fertility control for rodents-recent achievements and future directions

Management of overabundant rodents at a landscape scale is complex but often required to sustainably reduce rodent abundance below damage thresholds. Current conventional techniques such as poisoning are not species specific, with some approaches becoming increasingly unacceptable to the general public. Fertility control, first proposed for vertebrate pest management over 5 decades ago, has gained public acceptance because it is perceived as a potentially more species-specific and humane approach compared with many lethal methods. An ideal fertility control agent needs to induce infertility across one or more breeding seasons, be easily delivered to an appropriate proportion of the population, be species specific with minimal side-effects (behavioral or social structure changes), and be environmentally benign and cost effective. To date, effective fertility control of rodents has not been demonstrated at landscape scales and very few products have achieved registration. Reproductive targets for fertility control include disrupting the hormonal feedback associated with the hypothalamic-pituitary-gonadal axis, gonad function, fertilization, and/or early implantation. We review progress on the oral delivery of various agents for which laboratory studies have demonstrated efficacy in females and/or males and synthesize progress with the development and/or use of synthetic steroids, plant extracts, ovarian specific peptides, and immunocontraceptive vaccines. There are promising results for field application of synthetic steroids (levonorgestrel, quinestrol), chemosterilants (4-vinylcyclohexene diepoxide), and some plant extracts (triptolide). For most fertility control agents, more research is essential to enable their efficient and cost-effective delivery such that rodent impacts at a population level are mitigated and food security is improved.

Immunocontraception of male and female giraffes using the GnRH vaccine Improvac®

The aim of this study was to develop protocols for contraception in both sexes of giraffes (Giraffa camelopardalis) by using the GnRH vaccine Improvac®. We evaluated the success of immunization by analyzing fecal reproductive hormone metabolites in female (n = 20) and male (n = 9) giraffes. Endocrine analysis provided the basis for the successful immunization protocol, as well as for assessing long-term effects. Reliable reduction of fecal steroid metabolites to baseline levels in female giraffes was achieved with three, and in males with four or five injections at 4-week intervals. Effective booster injections were administered at 2-month intervals in the first year of treatment and at three to 4-month intervals in the following years. In addition to endocrine analysis, we determined vaccination efficacy in bulls by assessing testicular atrophy. Long-term (>2 years) use in females was often accompanied by prolonged periods of persistent corpus luteum activity, although normal cycles were not observed. Problems might occur with reversibility, because in a few males and females, even after more than 2 years since treatment had been stopped, fecal hormone metabolites have not returned to pretreatment levels. The results are somewhat ambiguous, as reproduction can be suppressed by use of Improvac®, but the question of reversibility remains unsolved.

Long-term effect of repeated deslorelin acetate treatment in bitches for reproduction control

Long-acting gonadotropin-releasing hormone (GnRH) analogs, which are approved for male dogs and ferrets, have been used off-label to suppress estrus in bitches predisposed to the side effects of spaying. Health data from the past 12 years were evaluated from bitches without progestogen pretreatment that received deslorelin acetate (DA) to suppress estrus for the first time before the age of 4.5 years. The study population included 32 client-owned bitches repeatedly treated with either 4.7 mg or 9.4 mg DA implants for a period of 5.3 ± 3.4 years (range 0.5-11.3 years). Follow-up information concerning immediate side effects of DA occurring within five months after the first DA treatment (n = 23) as well as long-term side effects of sustained gonadal suppression occurring after five months up to three years (n = 2), three years up to five years (n = 2) or more than five years (n = 8) were assessed through a questionnaire. Treatment was considered successful if no major side effects requiring medical treatment occurred, which applied to 26 out of 32 (81 %) bitches. In the six remaining bitches, the following major side effects led to treatment discontinuation: persistent urinary incontinence (n = 1), reoccurring induced heat (n = 1), uterine disease (n = 3) and/or ovarian tumor (n = 3). The bitches recovered completely after surgical spaying and/or DA implant removal. Minor side effects that did not require therapy or affect animal welfare included body weight changes (n = 18), subtle behavioral changes (n = 13), induced heat (n = 12), coat changes (n = 11), pseudocyesis (n = 6), transient urinary incontinence (n = 4), and/or temporary thickening of the uterine wall with little anechogenic content (n = 2). To examine a possible causal relationship between adverse side effects and DA treatment, further studies should compare the frequency of pathologies between groups of GnRH-treated, intact and spayed bitches of similar breeds and ages. Nevertheless, DA application before the age of 4.5 years may be a means of postponing surgical spaying for several years in breeds at high risk for developing urinary incontinence. Before DA is used in bitches, owners should be fully informed regarding possible side effects.

Effectiveness of a New Recombinant antiGnRH Vaccine for Immunocastration in Bulls

Simple Summary

Castration of males is a common procedure in cattle production. Surgical procedures are most commonly used, but there is an increasing interest in non-invasive alternatives to avoid risk of infection, bleeding, pain, stress and to improve animal welfare. Immunization against gonadotropin-releasing hormone is currently being used in livestock, but there is only one commercially available vaccine for cattle and results regarding the number of doses needed to maintain castration are variable. The efficacy, safety, and production parameters of a new antigen for immunocastration in bulls was assessed. Results showed that two doses of the vaccine to 40 10-month-old bulls achieved testosterone suppression below productive performance. Live weight at slaughter and carcass yield was greater in immunized animals than in surgically castrated cattle. Castration effects of the vaccine were maintained until the end of the trial at 24 weeks.

Abstract

Castration by surgical techniques is common in livestock; however, post-surgery complications and concerns for animal wellbeing have created a need for new non-invasive alternatives. The objective of this study was to evaluate immunocastration in bulls using antigen GnRX G/Q; a recombinant peptide proved to be effective in laboratory and companion animals. A nine-month trial with 80 9-month-old Normand x Hereford bulls, kept in a pastured system, was conducted. The herd was divided in half with 40 bulls surgically castrated (SC) and 40 castrated by immunization against GnRH (IC). The antigen was injected on days 0 and 40 of the experiment. After the second dose, the IC group had elevated GnRH antibodies and decreased testosterone levels (below 5 ng/mL) that were maintained for 23 weeks. At slaughter on day 190, the immunocastrated group obtained a higher weight, hot carcass, and dressing percentage than the SC group. There was no difference in pH, color of meat, fat coverage, cooking loss, or tenderness between groups. The bulls showed no inflammatory reaction at the injection site or adverse side effects from the vaccine. Our results demonstrate that immunocastration with GnRX G/Q is an efficient and safe alternative to surgical castration in livestock. Additional work evaluating antigen effects over a longer period is needed to validate commercial viability.

Interval between Removal of a 4.7 mg Deslorelin Implant after a 3-, 6-, and 9-Month Treatment and Restoration of Testicular Function in Tomcats

Deslorelin implants have been used to produce a reversible sterilization in several species. In cats, the prolonged duration (12-15 months in tomcats and 18-22 months in queen) is often too much for cat breeders who request early implant removal. The interval between implant removal and resumption of reproductive function in cats has never been investigated. Eighteen tomcats received a 4.7 mg deslorelin implant placed in the periumbilical area and surgically removed during all seasons of the year after 3, 6, or 9 months (n = 6, 6, and 6 cats, respectively). Following implant removal, all cats received a clinical exam every two weeks, including testicular ultrasonographic measurement, observation of penile spikes, and blood collection for serum testosterone assay. Restoration of serum testosterone secretion occurred after 23 ± 6, 23 ± 6, and 22 ± 7 days in the 3-, 6-, and 9-month groups, respectively. Restoration of testicular function was confirmed by histology in 13/15 cats undergoing orchiectomy at the end of the study while the owners of the remaining two cats opted to maintain their animals intact. Removal of a 4.7 mg deslorelin implant after 3, 6, or 9 months is followed by resumption of serum testosterone secretion after about 3 weeks independent of age or season.

Role of GnRH Isoforms in Paracrine/Autocrine Control of Zebrafish (Danio rerio) Spermatogenesis

It is well established that hypothalamic GnRH (gonadotropin-releasing hormone) is one of the key peptides involved in the neuroendocrine control of testicular development and spermatogenesis. However, the role of GnRH as a paracrine regulator of testicular function has not been fully investigated. The present study demonstrates the presence of GnRH and its receptors in the zebrafish (Danio rerio) testis, and provides information on direct action of native GnRH isoforms (GnRH2 and GnRH3) on different stages of spermatogenesis in this model. Both GnRH2 and GnRH3 stimulated basal spermatogenesis by increasing numbers of type Aund spermatogonia, spermatozoa, and testosterone release, and in this study GnRH2 exerted higher relative activity than GnRH3. Next, we evaluated the effects of GnRH isoforms on human chorionic gonadotropin (hCG)- and follicle-stimulating hormone (Fsh)-induced spermatogenesis. The 2 GnRH isoforms were found to have different effects on Fsh- and hCG-induced response depending on the stage of spermatogenesis and concentration of the peptides. The results provide strong support for the hypothesis that locally produced GnRH2 and GnRH3 are important components of the complex multifactorial system that regulates testicular germinal cell development and function in adult zebrafish.

Reproductive and Behavioral Evaluation of a New Immunocastration Dog Vaccine

Simple Summary

Population control of free-roaming dogs is a topic of great interest worldwide. Immunocastration (immune blockade of GnRH-I, the hormone that commands reproductive ability) has emerged as a complementary alternative to surgical castration. In this work, the effectiveness of an immunocastration vaccine for dogs was evaluated, as were the reproductive and behavioral characteristics of vaccinated animals. Two consecutive trials were carried out for this purpose. A first trial was conducted under experimental conditions, observing an immune response against the vaccine over a nine-month period that was associated with changes in the testicular function of the animals (decrease in testosterone and alteration of the characteristics of the ejaculate). The second trial was conducted on dogs who had owners, and vaccinated animals showed an immune response against the five-month vaccine and a decrease in unwanted behaviors associated with the presence of sex hormones. While more studies are needed, this vaccine is emerging as a promising tool for the reproductive and behavioral management of male dogs.

Abstract

Canine immunocastration development has been of interest for many years as a complementary strategy to surgical castration. The purpose of this paper was to verify the effect of a recombinant vaccine for dog immunocastration. Two tests were done, one under controlled conditions and a second under field conditions. Animals were injected with 1 mL of 500 µg GnRXG/Q recombinant protein; 500 µg of low molecular weight chitosan as adjuvant; 1 mL NaCl 0.9% q.s. In the first trial, eight Beagle male dogs between the ages of 1 and 3 comprised the sample, randomly divided into two groups: vaccinated group (n = 7) and control group (n = 2). The second trial had 32 dogs with owners. In the first controlled conditions trial, the vaccine produced specific antibodies that remained until the end of the trial (day 270), inducing reduced testosterone and spermiogram changes in the immunized animals. In a second trial, on the field, specific immunity was induced, which remained high up to day 150. The vaccine also reduced sexual agonistic and marking behaviors. This new vaccine proved to be safe, immunogenic, capable of reducing gonadal functionality, and had a positive effect on inducing reduced sexual, agonistic, and marking behavior of the animals.

BOARD INVITED REVIEW: Immunocontraception as a possible tool to reduce feral pig populations: recent and future perspectives

The feral pig populations of many countries continue to increase. Scientific studies on population size are scarce, while the numbers of reported observations on presence of and damage caused by feral pigs are increasing. Feral pigs can carry and spread several diseases (including zoonotic), but African Swine Fever (ASF) is of most concern. It is a highly transmissible viral disease associated with an extremely high mortality rate. Since 2009 ASF has appeared in several European countries, with cases being identified first among local feral pigs and consequently in domestic pig production units, indicating a clear linkage with the movement of the feral pig population and the spread of the disease across national boundaries. Control of feral pig populations is currently under discussion. Because massive culling raises questions of animal welfare and ethics, fertility control could represent an important and effective means to control feral pig populations. Contraceptive vaccines have been used with some degree of success in many wild species because they are able to provide a long-term effect without any consequent health problems. However, extensive and efficacious use of vaccines to control feral pig populations is not simple. The aim of this article was to review the progress in immunocontraception use in feral pigs, providing an account of the current status and future perspectives.

Fertility Control in Wildlife: Review of Current Status, Including Novel and Future Technologies

Wildlife conservation requires varying degrees of management of endangered species as well as management of their potential predators and competitors. Conservation also depends on ameliorating human-wildlife conflict, especially where there is a threat to the safety of people and of their pets and livestock. In addition, sustainability of wildlife populations can be affected by feral domestic animals or invasive species, that require removal or control. With the increasing concern for animal welfare, non-lethal methods of limiting population size and distribution, such as fertility control, are gaining favor. Breeding programs in zoos depend on highly effective and selective contraception to manage sustainable insurance populations. This review covers fertility control methods currently in use, those that have not lived up to past promises, and others that are under development and present hope for addressing remaining challenges.

Effect of addition of buserelin acetate to the extender on motility and viability of bovine spermatozoa

The present study was aimed to determine the effect of GnRH analog (buserelin acetate) on the quality of bovine spermatozoa stored at 16° C for 24 h. Semen collected in the summer season from June to September from healthy Polish Holstein-Friesian bulls. Ejaculates were centrifuged, divided and diluted to the final concentration of 240 × 10⁶ spermatozoa/mL using animal protein-free commercial BIOXcell^® extender (IMV Technologies, L'aigle, France) (Control) or with BIOXcell^® extender supplemented with buserelin acetate and stored 0, 8 and 24 h. Sperm motility parameters analysis was performed using a computer-assisted sperm analysis (CASA) system. The viability of spermatozoa was performed using flow cytometer. The addition of buserelin acetate to BIOXcell^® extender did positively affect the total motility (was higher in the observed samples with the addition of 2 µg/mL and 4 µg/mL than in the control group), progressive motile (forward progressing sperm was significantly increased (p < 0.05) over the control group at the 0 h and 8 h of incubation following the supplementation of 2, 4 and 8 μg/mL buserelin acetate) and viability of spermatozoa (the number of live spermatozoa was significantly higher (p < 0.05) in 2 µg/mL and 4 µg/mL samples with buserelin acetate at 8th hour of incubation and in sample with 4 µg/mL at 24th hour of incubation compared to the control group). We recommend adding 4 µg/mL to the extender to improve the quality of bovine semen.

Breeding in the fat-tailed dunnart following ovarian suppression with the gonadotrophin-releasing hormone agonist Lucrin® Depot

Lucrin Depot (AbbVie), a 1-month microsphere gonadotrophin-releasing hormone (GnRH) agonist preparation, was investigated as a potential agent to synchronise cycling in the fat-tailed dunnart (Sminthopsis crassicaudata). Forty-eight randomly selected females were treated with 5 or 10mgkg-1 Lucrin Depot (n=24 per dose). Eighteen females per treatment had their reproductive activity scored at 4, 8, 12 and 16 weeks using two ovarian (Graafian follicle and corpus luteum status) and two reproductive tract (uterine and vaginal muscularity and vascularity) parameters that formed a reproductive activity score. Six females per treatment were paired with a male at 4 weeks. Fertility was assessed between 8 and 16 weeks by pouch check, and thereafter by dissection. The effects of the 5 and 10mgkg-1 doses were statistically equivalent. Females showed suppression at 4-8 weeks, an increase in reproductive activity at 8-12 weeks and all were cycling normally at 16 weeks. Six pouch young were born at 12 weeks to two females treated with the 5mgkg-1 dose. Nine embryos were recovered at 16 weeks from two females treated with the 10mgkg-1 dose. In conclusion, Lucrin Depot can suppress breeding, and fertile mating can occur in subsequent cycles in the dunnart. There is potential for Lucrin Depot to be used as an assisted breeding tool, but it may need to be combined with ovarian stimulation treatment to achieve practical levels of synchronisation in the fat-tailed dunnart.

A role for selective contraception of individuals in conservation

Contraception has an established role in managing overabundant populations and preventing undesirable breeding in zoos. We propose that it can also be used strategically and selectively in conservation to increase the genetic and behavioral quality of the animals. In captive breeding programs, it is becoming increasingly important to maximize the retention of genetic diversity by managing the reproductive contribution of each individual and preventing genetically suboptimal breeding through the use of selective contraception. Reproductive suppression of selected individuals in conservation programs has further benefits of allowing animals to be housed as a group in extensive enclosures without interfering with breeding recommendations, which reduces adaptation to captivity and facilitates the expression of wild behaviors and social structures. Before selective contraception can be incorporated into a breeding program, the most suitable method of fertility control must be selected, and this can be influenced by factors such as species life history, age, ease of treatment, potential for reversibility, and desired management outcome for the individual or population. Contraception should then be implemented in the population following a step-by-step process. In this way, it can provide crucial, flexible control over breeding to promote the physical and genetic health and sustainability of a conservation dependent species held in captivity. For Tasmanian devils (Sarcophilus harrisii), black-flanked rock wallabies (Petrogale lateralis), and burrowing bettongs (Bettongia lesueur), contraception can benefit their conservation by maximizing genetic diversity and behavioral integrity in the captive breeding program, or, in the case of the wallabies and bettongs, by reducing populations to a sustainable size when they become locally overabundant. In these examples, contraceptive duration relative to reproductive life, reversibility, and predictability of the contraceptive agent being used are important to ensure the potential for individuals to reproduce following cessation of contraception, as exemplified by the wallabies when their population crashed and needed females to resume breeding.

Ultrasonographic characteristics of the reproductive tract and serum progesterone and estradiol concentrations in captive female red wolves (Canis rufus) with and without reproductive tract disease

OBJECTIVE To describe ultrasonographic characteristics of the reproductive tract and serum progesterone and estradiol concentrations in captive female red wolves (Canis rufus) with and without reproductive tract disease. DESIGN Prospective study. ANIMALS 13 adult female red wolves. PROCEDURES Wolves with varying parity and history of contraceptive treatment were anesthetized to facilitate ultrasonographic examination and measurement of the reproductive tract and blood collection for determination of serum progesterone and estradiol concentrations in December 2011 and June 2012. Additionally, during the December evaluation, fine-needle aspirate samples of the uterus were obtained for cytologic evaluation. Measurements were compared between wolves with and without reproductive tract disease and between wolves that had and had not received a contraceptive. RESULTS 7 of 13 wolves had or developed reproductive tract disease during the study. Ranges for measurements of reproductive tract structures overlapped between ultrasonographically normal and abnormal tracts, but measurements for abnormal tracts were generally greater than those for normal tracts. The ultrasonographic diagnosis was consistent with the histologic diagnosis for reproductive tracts obtained from wolves that were sterilized, were euthanized, or died during the study. Cytologic results for fine-needle aspirate samples of the uterus and serum progesterone and estradiol concentrations were unable to distinguish wolves with and without reproductive tract disease. Reproductive tract disease was not associated with parity or contraceptive administration. CONCLUSIONS AND CLINICAL RELEVANCE The ultrasonographic images, reproductive tract measurements, and descriptions of reproductive tract lesions provided in this study can be used as diagnostic guidelines for the treatment and management of red wolves with reproductive tract disease.

Recent advances in tools and technologies for monitoring and controlling ovarian activity in marsupials

Components of assisted reproduction technologies (ART), such as sperm cryopreservation, artificial insemination, superovulation and pouch young surrogacy, have been developed for a range of Australian and American marsupials. However, methods to effectively control ovarian function, arguably the key limiting factors in applying and integrating ART as a practical tool in conservation management, remain poorly developed. This is largely due to unique characteristics of the marsupial corpus luteum and its failure to respond to agents used to synchronize ovarian function in eutherian mammals. This paper presents an overview of relevant aspects of marsupial reproductive biology across marsupial taxonomic groups including information on the long-established technique of removal of suckling young to activate ovarian cycles. Ovarian monitoring tools for marsupials are reviewed and their usefulness for ART assessed (laparotomy, hormone cycling, vaginal cytology, laparoscopy and ultrasonography). We also discuss promising recent work examining the potential of manipulating hypothalamic-pituitary function using GnRH agonists and antagonists as the basis of ovarian control (female synchronization) strategies.

The immune profile induced is crucial to determine the effects of immunocastration over gonadal function, fertility, and GnRH-I expression

PROBLEM

Immunocastration or vaccination against the GnRH-I hormone is a promising alternative to reproductive control in different animal species. Given the low immunogenicity of this hormone, the use of adjuvants becomes necessary.

METHOD OF STUDY

This study evaluated the effects of three adjuvants that induce different immune response profiles over gonadal function, fertility, and expression of GnRH-I. Female mice (n = 6) were vaccinated at days 1 and 30 with a recombinant antigen for immunocastration and different adjuvants that induced preferentially Th1/Th2, Th2, and Th1 immune profiles.

RESULTS

Th1/Th2 response is the most efficient to block reproductive activity in vaccinated animals, reducing the number of luteal bodies and pre-ovulatory follicles. Th2 and Th1/Th2 responses induced an increase in GnRH-I at the hypothalamus.

CONCLUSION

The immune profile induced by different adjuvants is essential on the effects over fertility, gonadal function, and hypothalamic GnRH-I expression in immunocastrated animals.

Non-surgical sterilisation methods may offer a sustainable solution to feral horse (Equus caballus) overpopulation

Feral horses are a significant pest species in many parts of the world, contributing to land erosion, weed dispersal and the loss of native flora and fauna. There is an urgent need to modify feral horse management strategies to achieve public acceptance and long-term population control. One way to achieve this is by using non-surgical methods of sterilisation, which are suitable in the context of this mobile and long-lived species. In this review we consider the benefits of implementing novel mechanisms designed to elicit a state of permanent sterility (including redox cycling to generate oxidative stress in the gonad, random peptide phage display to target non-renewable germ cells and the generation of autoantibodies against proteins essential for conception via covalent modification) compared with that of traditional immunocontraceptive approaches. The need for a better understanding of mare folliculogenesis and conception factors, including maternal recognition of pregnancy, is also reviewed because they hold considerable potential in providing a non-surgical mechanism for sterilisation. In conclusion, the authors contend that non-surgical measures that are single shot and irreversible may provide a sustainable and effective strategy for feral horse control.

Effectiveness of an immunocastration vaccine formulation to reduce the gonadal function in female and male mice by Th1/Th2 immune response

Immunocastration has emerged as an alternative to surgical castration in different animal species. This study examined the effectiveness of a new vaccine formulation for immunocastration using the biopolymer chitosan as adjuvant. First, female and male mice (n = 4), in three subsequent experiments were vaccinated at Days 1 and 30 of the study, to determine the immune response profile and gonadal alterations due to immunization. The results demonstrated that the vaccine was able to elicit strong antibody responses against native GnRH hormone (P < 0.01), with a T helper (Th) 1/Th2 immune response profile. Along with this, a suppression of gonadal activity with a decrease of luteal bodies (1.08 ± 0.22 and 4.08 ± 0.39) and antral follicles (1.17 ± 0.32 and 4.5 ± 0.38) in the ovaries of immunized females and control, respectively, and a reduction of seminiferous tubules size (142.3 ± 5.58 mm and 198.0 ± 6.11 mm) and germinal cellular layers (3.58 ± 0.26 and 5.08 ± 0.29) of immunized males and control animals, respectively, were observed (P < 0.01). Then, in a study of long-term immune response due to vaccination in female and male mice (n = 4) from two subsequent experiments, a suppression of gonadal function and an induction of a Th1/Th2 immune response was also observed, determined by both, immunoglobulin and cytokine profiles, which lasted until the end of the study (7 months; P < 0.01). The findings of this study have demonstrated that vaccination with a new immunocastration vaccine inducing a Th1/Th2 immune response against GnRH (P < 0.01) elicit a decrease of gonadal function in male and female mice (P < 0.01). Owing to long-term duration of the antibody levels generated, this vaccine formulation appears as a promising alternative for immunocastration of several animal species where long-lasting reproductive block is needed.

Ovarian suppression in a marsupial following single treatment with a gonadotrophin-releasing hormone agonist in microspheres

The effect of treatment with Lucrin Depot (1 month), a microsphere gonadotrophin-releasing hormone agonist preparation, was investigated in the fat-tailed dunnart (Sminthopsis crassicaudata) as a potential strategy to synchronise cycling. The status of the ovaries (ovarian size, number and size of Graafian follicles and corpora lutea) and reproductive tract (weight, vascularity and muscularity) in twelve untreated females were assessed to establish the activity parameters for randomly selected cycling animals. Thirty-six females were treated with 1 mg kg–1 (n = 12), 10 mg kg–1 (n = 12) or 20 mg kg–1 (n = 12) Lucrin Depot. At 4, 6 and 8 weeks the reproductive tracts were assessed using the criteria developed in the untreated females. All of the females treated with 10 mg kg–1 showed suppression at 4 weeks and 25% showed return of reproductive activity at 8 weeks. A dose of 1 mg kg–1 did not appear to suppress reproductive activity and 20 mg kg–1 gave equivocal results, with evidence of both suppression and activity. The results indicate that Lucrin Depot appears to be a promising agent to regulate and potentially synchronise breeding activity in the fat-tailed dunnart.

Finding the Balance: Fertility Control for the Management of Fragmented Populations of a Threatened Rock-Wallaby Species

Simple Summary

Black-flanked rock-wallabies (Petrogale lateralis lateralis) can reach high numbers in fragmented populations in the West Australian wheat-belt, where they can damage crops and cause habitat degradation. As they are threatened, we wanted a non-permanent control method that did not adversely affect the body condition of treated females compared to untreated females, using body condition as an indicator of general health and fitness. We gave adult female rock-wallabies deslorelin contraceptive implants to suppress their fertility and monitored the impact for three years. Treated females did not conceive new young for over two years. We did not detect any negative effects on body condition, suggesting that deslorelin may be an effective tool for managing overabundant populations of marsupials.

Abstract

Populations of Australian marsupials can become overabundant, resulting in detrimental impacts on the environment. For example, the threatened black-flanked rock-wallaby (Petrogale lateralis lateralis) has previously been perceived as overabundant and thus ‘unwanted’ when they graze crops and cause habitat degradation. Hormonally-induced fertility control has been increasingly used to manage population size in other marsupials where alternative management options are not viable. We tested whether deslorelin, a superagonist of gonadotropin-releasing hormone (GnRH), would suppress reproduction in free-living adult female rock-wallabies without adversely impacting body condition. We trapped, synchronised reproduction and allocated female rock-wallabies to a placebo implant (control, n = 22), one (n = 22) or two (n = 20) subcutaneous implants of deslorelin. Females were then recaptured over the following 36 months to monitor reproduction, including Luteinising Hormone levels, and body condition. Following treatment, diapaused blastocysts reactivated in five females and the resulting young were carried through to weaning. No wallabies treated with deslorelin, conceivede a new young for at least 27 months. We did not observe adverse effects on body condition on treated females. We conclude that deslorelin implants are effective for the medium-term suppression of reproduction in female black-flanked rock-wallabies and for managing overabundant populations of some marsupials.

GnRH-agonist implantation of prepubertal male cats affects their reproductive performance and testicular LH receptor and FSH receptor expression

This study was conducted to investigate the effect of GnRH-agonist implantation in prepubertal tomcats on sexual behavior, reproductive performance, and expression of testicular LH receptor (LHR) and FSH receptor (FSHR) and also to compare the testicular characteristics, LHR and FSHR expression between prepubertal and adult tomcats. In experiment 1, 3-month-old tomcats (n = 6/group) were either treated with or left without 4.7 mg deslorelin implants. Semen collection and evaluation were performed just before castration at 48 weeks after treatment; removed testes were analyzed for mRNA and protein expression of LHR and FSHR. We were able to collect semen from six non-treated cats, whereas in treated cats, semen was uncollectable. The results revealed that sexual behavior was absent in the implanted cats throughout the study period. Testicular volume was found to decrease from 30 weeks after treatment onward in the implanted cats compared to the controls (P < 0.05). Semen production was found only in non-implanted cats. Testicular tissue score, seminiferous tubule diameter, and LHR protein expression were found lower in the implanted cats (P < 0.05), but no differences were observed in mRNA expression of LHR and protein expression of FSHR between groups. The mRNA expression of FSHR was higher in the implanted (P < 0.05) compared to control cats. In experiment 2, testes from prepubertal (n = 6) and adult (n = 6) male cats were collected after castration and analyzed for mRNA and protein expression of LHR and FSHR. No differences were observed in the protein expression of LHR and FSHR between the two groups, whereas mRNA expression of FSHR was higher in prepubertal cats (P < 0.05). Testicular and epididymal weight, diameter of seminiferous tubules, and the testicular grade were higher in the adult compared to prepubertal cats (P < 0.05). In conclusion, deslorelin implants suppressed protein expression of LHR and enhanced mRNA expression of FSHR along with suppression of reproductive function without any adverse effects for at least 48 weeks in male cats.

Clinical use of deslorelin (GnRH agonist) in companion animals: a review

Over the years, many contraceptive medications have been developed for companion animals, but many secondary adverse effects have limited their use. A major advancement was achieved with the use of gonadotropin-releasing hormone (GnRH) analogues, mainly GnRH agonists, which mimic the effects of native GnRH. The development of effective low-dose, slow-release implants with potent agonists such as deslorelin (Suprelorin®, Virbac) have allowed their use to become widespread in recent years, with many potential benefits in companion animals. While the major application of deslorelin was initially male contraception, due to its two differing actions, either the stimulation of oestrus or the sterilization of fertility, its use has been increasing in the bitch as well. The aim of this study is to review the applications of deslorelin GnRH agonist implants in companion animal, such as dogs, cats and some exotic pets.

Use of the gonadotrophin-releasing hormone antagonist azaline B to control the oestrous cycle in the koala (Phascolarctos cinereus)

The present study examined the effectiveness of the gonadotrophin-releasing hormone (GnRH) antagonist azaline B to suppress plasma LH and 17β-oestradiol concentrations in koalas and its potential application for oestrous synchronisation. In Experiment 1, single subcutaneous injections of azaline B successfully blocked the LH response to exogenous mammalian (m) GnRH in a dose-dependent manner; specifically, 0 mg (n = 4) did not suppress the LH response, 1 mg azaline B (n = 6) suppressed the LH response for 24 h (P < 0.05), 3.3 mg azaline B (n = 8) suppressed the LH response significantly in all animals only for 3 h (P < 0.05), although in half the animals LH remained suppressed for up to 3 days, and 10 mg azaline B (n = 4) suppressed the LH response for 7 days (P < 0.05). In Experiment 2, daily 1 mg, s.c., injections of azaline B over a 10-day period during seasonal anoestrus (June-July; n = 6) suppressed (P < 0.01) the LH response to mGnRH consecutively over the 10-day treatment period and, 4 days after cessation of treatment, the LH response had not recovered. Experiment 3 was designed to test the efficacy of daily 1 mg, s.c., azaline B over 10 days to suppress plasma LH and 17β-oestradiol concentrations and ultimately synchronise timed return to oestrus during the breeding season. Although azaline B treatment did not suppress basal LH or 17β-oestradiol, oestrus was delayed in all treated females by 24.2 days, but with high variability (range 9-39 days). Overall, the present study demonstrates that the GnRH antagonist azaline B is able to inhibit the LH response in koalas to exogenous mGnRH and successfully delay the return to oestrus. However, although azaline B clearly disrupts folliculogenesis, it has not been able to effectively synchronise return to oestrus in the koala.

Fertility control in wildlife: review of current status, including novel and future technologies

Overpopulation of selected groups of animals is widely recognised as an issue that can have adverse effects on several current global problems, such as animal and human health, conservation and environmental changes. This review will, therefore, focus on recent novel contraception together with future technologies that may provide additional contraceptive methods.

Fertility control to mitigate human–wildlife conflicts: a review

As human populations grow, conflicts with wildlife increase. Concurrently, concerns about the welfare, safety and environmental impacts of conventional lethal methods of wildlife management restrict the options available for conflict mitigation. In parallel, there is increasing interest in using fertility control to manage wildlife. The present review aimed at analysing trends in research on fertility control for wildlife, illustrating developments in fertility-control technologies and delivery methods of fertility-control agents, summarising the conclusions of empirical and theoretical studies of fertility control applied at the population level and offering criteria to guide decisions regarding the suitability of fertility control to mitigate human–wildlife conflicts. The review highlighted a growing interest in fertility control for wildlife, underpinned by increasing numbers of scientific studies. Most current practical applications of fertility control for wild mammals use injectable single-dose immunocontraceptive vaccines mainly aimed at sterilising females, although many of these vaccines are not yet commercially available. One oral avian contraceptive, nicarbazin, is commercially available in some countries. Potential new methods of remote contraceptive delivery include bacterial ghosts, virus-like particles and genetically modified transmissible and non-transmissible organisms, although none of these have yet progressed to field testing. In parallel, new species-specific delivery systems have been developed. The results of population-level studies of fertility control indicated that this approach may increase survival and affect social and spatial behaviour of treated animals, although the effects are species- and context-specific. The present studies suggested that a substantial initial effort is generally required to reduce population growth if fertility control is the sole wildlife management method. However, several empirical and field studies have demonstrated that fertility control, particularly of isolated populations, can be successfully used to limit population growth and reduce human–wildlife conflicts. In parallel, there is growing recognition of the possible synergy between fertility control and disease vaccination to optimise the maintenance of herd immunity in the management of wildlife diseases. The review provides a decision tree that can be used to determine whether fertility control should be employed to resolve specific human–wildlife conflicts. These criteria encompass public consultation, considerations about animal welfare and feasibility, evaluation of population responses, costs and sustainability.

Gonadotropin-releasing hormone immunization for the treatment of urethral sphincter mechanism incompetence in ovariectomized bitches

We have investigated GnRH immunization for the treatment of urethral sphincter mechanism incompetence in ovariectomized bitches. It has been reported that decreasing LH secretion through the use of GnRH agonists temporarily restores continence in some bitches. Therefore, decreasing the circulating LH concentrations by immunizing against GnRH might temporarily maintain continence in incontinent dogs. Sixteen incontinent dogs given phenylpropanolamine (PPA) to control incontinence were recruited for this study. Eleven dogs were immunized against GnRH (novel treatment group) at week 0, and nine dogs were vaccinated again 4 weeks later. Five dogs (standard treatment group) were vaccinated with a placebo twice at 4-week intervals. PPA was discontinued in the novel treatment group 2 weeks after revaccination, and standard-treatment dogs were given PPA for the duration of the study. Blood samples were collected before each treatment and at 6, 8, 10, 12, 16, 20, and 24 weeks and owners recorded episodes of incontinence throughout the study. Ten of the eleven dogs in the novel treatment group experienced side effects as a result of vaccination; two of these dogs experienced more severe side effects after the first vaccination and were withdrawn from the study as a result. Of the nine dogs that completed the vaccination series, four dogs remained continent after PPA was discontinued. For these four dogs, there was no difference in incontinent episodes when they were given PPA versus treatment with the vaccine. All nine novel-treatment dogs developed a GnRH antibody titer and experienced a significant decrease in circulating LH concentrations. In conclusion, GnRH immunization was effective in maintaining continence in four of the nine incontinent ovariectomized dogs, and in these dogs, treatment with the vaccine was comparable with treatment with PPA.

Nonsurgical fertility control for managing free-roaming dog populations: a review of products and criteria for field applications

About 75% of dogs worldwide are free to roam and reproduce, thus creating locally overabundant populations. Problems caused by roaming dogs include diseases transmitted to livestock and humans, predation on livestock, attacks on humans, road traffic accidents, and nuisance behavior. Nonsurgical fertility control is increasingly advocated as more cost-effective than surgical sterilization to manage dog populations and their impact. The aims of this review were to 1) analyze trends in numbers of scientific publications on nonsurgical fertility control for dogs; 2) illustrate the spectrum of fertility inhibitors available for dogs; 3) examine how differences between confined and free-roaming dogs might affect the choice of fertility inhibitors to be used in dog population management; and 4) provide a framework of criteria to guide decisions regarding the use of nonsurgical fertility control for dog population management. The results showed that the 117 articles published between 1982 and 2011 focussed on long-term hormonal contraceptives, such as gonadotropin-releasing hormone agonists, immunocontraceptives, and male chemical sterilants. The number of articles published biennially increased from one to five papers produced in the early 1980s to 10 to 20 in the past decade. Differences between confined dogs and free-roaming dogs include reproduction and survival as well as social expectations regarding the duration of infertility, the costs of sterilization, and the responsibilities for meeting these costs. These differences are likely to dictate which fertility inhibitors will be used for confined or free-roaming dogs. The criteria regarding the use of fertility control for dog population management, presented as a decision tree, covered social acceptance, animal welfare, effectiveness, legal compliance, feasibility, and sustainability. The review concluded that the main challenges for the future are evaluating the feasibility, effectiveness, sustainability, and effects of mass nonsurgical sterilization campaigns on dog population size and impact as well as integrating nonsurgical fertility control with disease vaccination and public education programs.

Effects of a Commercial Canine Gonadotropin Releasing Hormone Vaccination on Intact Male Llamas and Alpacas

We have investigated the effect of immunization against gonadotropin releasing hormone (GnRH) using a commercial canine GnRH vaccine on testosterone concentration, testicular volume, testicular histology, and intermale behavior in intact male llamas and alpacas. Llamas (n=28) and alpacas (n=20) were either immunized (received 3 mL of vaccine given intramuscularly) or treated as controls (received 3 mL of sterile diluent given intramuscularly) at 0, 3, and 6 weeks. Blood samples and testicular volume measurements were taken at 0, 3, 6, 9, and 12 weeks. Owner surveys grading behavior at 0 and 12 weeks were received for 14 llamas. Two llamas at each time point undergoing the vaccination procedure were also castrated for testicular histological examination. Vaccinated animals elicited a GnRH antibody titer, and there was a significant decrease in testosterone concentration and testicular volume when compared with control animals. Intermale aggressive behavior was also significantly decreased in the surveyed llamas. However, histological examination revealed no significant changes. GnRH immunization using the canine GnRH vaccine may be an effective method for reducing intermale aggression in llamas and alpacas by decreasing circulating testosterone concentrations but cannot be recommended as an immunosterilant because of its lack of efficacy in interrupting spermatogenesis.

Chronic treatment of female tammar wallabies with deslorelin implants during pouch life: effects on reproductive maturation

The present study reports on attempts to delay puberty in a model marsupial species using the gonadotrophin-releasing hormone (GnRH) agonist deslorelin. Female tammar wallaby pouch young received deslorelin (5 mg) or placebo implants (n = 8/group) when they were 193 ± 2 days old. Sexual maturity was significantly delayed in deslorelin-treated animals, with the first successful production of offspring in treated and control animals occurring at 813 ± 62 and 430 ± 42 days of age, respectively. This delay was associated with a period of retarded pouch and teat development. Progesterone concentrations remained at basal levels throughout the first breeding season, indicating the absence of luteal cycles in treated females. Recovery and maturation of the hypothalamic–pituitary axis was a gradual process. Treated animals failed to respond to GnRH challenge at 12 months of age and had a reduced LH response at 18 months of age, before attaining full responsiveness by 24 months of age. Despite this apparent pituitary recovery by 24 months of age, as evidenced by complete teat eversion and LH responsiveness to GnRH, the time to first parturition was significantly delayed beyond this time in three females. This suggests that there may be longer-lasting effects at the level of the ovary and/or on FSH secretion. The significant delay in the onset of sexual maturation in response to chronic GnRH agonist treatment in this model marsupial species may be of practical significance to the management of fertility in captive and semi-free range marsupial populations.

Brushtail possums (Trichosurus vulpecula) in metropolitan Sydney: population biology and response to Suprelorin contraceptive implants

The cohabitation of the common brushtail possum (Trichosurus vulpecula) with people in urban areas often causes conflict. Basic biological parameters are needed to evaluate potential new management options such as fertility control. This study investigated the biology of an urban brushtail possum population and the effects of Suprelorin contraceptive implants on individual females within that population. Trapping success remained constant over time, with 2.8 ± 0.2 individuals trapped per residential property. Recapture rates for males declined rapidly over time, with only 30% of males recaptured on the same property 12 months after initial capture (n = 30) and no males recaptured after 18 months (compared with female recapture rates of 58% after 18 months, n = 33). These data, combined with the preponderance of males observed within the lower age classes, suggests that male possum turnover is high within urban areas. This may be partially compensated for by the male-bias (1.8 : 1) observed in pouch young. Breeding was seasonal with the main peak of births in autumn, and a secondary smaller peak in spring. Suprelorin contraceptive treatment effectively inhibited reproduction in adult females for a minimum duration of 519 ± 7 (n = 5) and ≥700 ± 20 (n = 5) days after administration of one or two 4.7-mg implants, respectively, with no negative side-effects obvious. The concurrent collection of data on contraceptive efficacy and population-specific life-history parameters provides a unique opportunity to highlight the importance of understanding local population dynamics when evaluating the likely efficacy and implementation of fertility control programs to manage problem wildlife.

Effect of intrauterine administration of gonadotropin releasing hormone on serum LH concentrations in lactating dairy cows

The objectives were to compare: (1) preovulatory serum LH concentrations, and (2) synchronization of ovulation, after im or iu administration of the second GnRH treatment of Ovsynch in lactating dairy cows. Lactating cows (N = 23) were presynchronized with two injections of PGF(2α) given 14 days apart (starting at 34 ± 3 days in milk), followed by Ovsynch (GnRH-7 d-PGF(2α)-56 h-GnRH) 12 days later. At the time of the second GnRH of Ovsynch (Hour 0), cows were blocked by parity and randomly assigned to 1 of 3 groups: (1) control group (CON; N = 7) were given 2 mL sterile water im; (2) intramuscular group (IM; N = 8) received 100 μg of GnRH im; and (3) intrauterine group (IU; N = 8) had 100 μg GnRH infused in the uterus (2 mL). Blood samples for serum LH concentrations were collected at Hours 0, 0.5, 1, 1.5, 2, 3, and 4. Furthermore, ultrasonography was performed twice daily (12-h intervals) from Hours 0 to 60 to confirm ovulation. The LH concentrations were greater (P < 0.05) in the IM than IU and CON groups at Hours 0, 0.5, 1, 1.5, 2, 3, and 4. Although LH concentrations were numerically higher in the IU group, LH concentrations within the IU and CON groups did not change over time. More cows ovulated in the IM (8/8) and IU (7/8) groups within 60 h after the second GnRH administration compared with the CON (2/7) group. In summary, serum LH concentrations were lower in the IU versus IM group, but the proportion of cows that ovulated within 60 h was similar between these two groups. Therefore, iu administration of GnRH may be an alternative route of delivery to synchronize ovulation in beef and dairy cattle.