Use of GnRH-agonists for medical management of reproductive disorders in birds

Medullary bone in male budgerigars (Melopsittacus undulatus) with testicular neoplasms

Medullary bone is a calcium-rich, labile bone normally occurring in female birds with each egg-laying cycle. The stimulus for formation of medullary bone is, in part, the cyclic increase in serum estrogens produced by preovulatory ovarian follicles. Increased bone density due to formation of medullary bone, particularly in pneumatic bones, has been termed polyostotic hyperostosis, even if physiologic. This study investigated the formation of medullary bone in nonpneumatic (femur) and pneumatic (humerus) bones in sexually mature male budgerigars submitted for autopsy. Of the 21 sexually mature male budgerigars submitted for autopsy, 7 (33%) had medullary bone in 1 or more bones examined. All 7 male budgerigars with medullary bone had a testicular neoplasm, which was morphologically consistent with a testicular sustentacular cell tumor, seminoma, or interstitial cell tumor. Medullary bone was not present in the 14 cases with other diseases. Medullary bone formation in pneumatic and nonpneumatic bones can occur in male budgerigars with testicular neoplasms. Radiographic increases in medullary bone density, particularly in the humerus, could provide antemortem indication of testicular neoplasia in male budgerigars.

DESLORELIN (SUPRELORIN®) USE IN NORTH AMERICAN AND EUROPEAN ZOOS AND AQUARIUMS: TAXONOMIC SCOPE, DOSING, AND EFFICACY

The Association of Zoos and Aquariums Reproductive Management Center (RMC) in the US and the European Association of Zoos and Aquaria Reproductive Management Group (RMG) in Europe monitor efficacy of contraceptive products in participating institutions and use those results to inform contraceptive recommendations. This study used the joint RMC-RMG Contraception Database to analyze efficacy of deslorelin implants (Suprelorin^®), a contraceptive used in a wide range of mammalian taxa. More recently its use has increased in birds and in some reptiles and fish. Deslorelin, a gonadotropin-releasing hormone (GnRH) agonist, stimulates the reproductive system before downregulating receptors on pituitary cells that produce hormones that stimulate gonadal steroids in both males (testosterone) and females (estradiol and progesterone), interrupting sperm production and ovulation, respectively. Nevertheless, it has been used mostly in females. Efficacy has been high in mammals, with failures resulting in offspring in only 1.3% of treated individuals and 0.5% of treatment bouts. The failure rate has been higher in birds, with 14.7% of individuals in 7.2% of bouts producing eggs, perhaps reflecting differences in avian GnRH molecules. Too few reptiles and fish have been treated for meaningful analysis. Although deslorelin appears very safe, a possible exception exists in carnivores, because the stimulatory phase can result in ovulation and subsequent sustained progesterone secretion that may cause endometrial pathology. However, the stimulatory phase can be prevented by treatment with megestrol acetate for 7 d before and 7 d after implant insertion. The two current formulations of Suprelorin are effective for minimums of 6 (4.7 mg) or 12 mo (9.4 mg). The data indicate that Suprelorin is an effective and safe contraceptive option for female mammals, although it may not be effective in males of some mammalian species. Further research is needed to ascertain its usefulness in nonmammalian taxa.

Induction of reproductive activity and egg production by gonadotropin-releasing hormone in non-laying hens

The current study was conducted to evaluate the effects of gonadotropin-releasing hormone (GnRH) analogue (Receptal) injection on reproductive traits of fully mature layers hens (32 weeks) suffered from inactive ovaries. Ninety-six non-laying hens (TETRA-SL brown egg layers), selected from a commercial flock, with similar body weight, were randomly assigned to four groups (n = 24). Hens in the 1st group served as a control. Hens of the 2nd, 3rd and 4th groups were individually intramuscularly injected every 4 days with 50, 100 and 150 µl of Receptal solution, respectively, for two times. The results stated that the injection of Receptal induced the non-laying hens to produce eggs, but control birds did not produce eggs during the experimental period. The distance between pelvic bones and between the pelvic bone and keel bone of hens was significantly improved (p < .001) in groups received different GnRH levels compared with the control group. The best results were observed in the group injected with 100 µl Receptal. Levels of LH, FSH, oestrogen and progesterone hormones were significantly (p < .05) higher in Receptal-treated groups than in the control group. Hens injected with Receptal had an increase in ovary%, yellow follicles number, oviduct% and oviduct length (p < .001) compared with the control. It was concluded that treating inactive ovaries in non-laying hens with GnRH injections for two times, 4-day intervals, is an effective procedure for inducing egg production and useful in cost reduction in layer farms, and the group treated with 100 µl Receptal had the best results.

[GnRH agonist implants in small animal practice - what do we know 13 years following EU registration?]

The availability of GnRH agonist implants offers the possibility of a reversible, temporary downregulation of endocrine and germinative testicular function in male dogs and hobs. This review provides an overview of the registered indication, the induction of temporary infertility in healthy, intact, sexually mature male dogs (4.7 and 9.4 mg deslorelin) and hobs (9.4 mg deslorelin) as well as various off-label indications. Off-label use requires strict indications, informed consent from the owner and a lack of licensed medication (safe and optimum effect). Off-label indications in the male dog include sexual-hormone dependant (disturbing) behavior, benign prostatic hyperplasia, small adenomas of the hepatoid glands and alopecia X. Successful use of deslorelin implants for estrus suppression in jils, but also for the treatment of hyperadrenocorticism in ferrets in general have been described. Similarly, hormonal castration can be induced in tomcats and queens. The variable time to onset of effect and its duration (extremely variable in some animals) represent a challenge for breeders. No (sufficient) contraceptive activity was identified in male rabbits and male guinea pigs; however, treatment did successfully suppress the estrus cycle in female individuals of these species, as well as reproductive activity in male and female rats. Regarding the use in birds and reptiles, significant species-specific differences exist with regard to efficacy, time until onset of effect and duration of downregulation. In birds, the implant is efficient to fully suppress egg laying in chicken, Japanese quail and psittacids. In doves, egg laying is only significantly reduced. Successful treatment of reproduction-associated (unwanted) behaviour patterns (feather picking, aggression) has also been described. In some male birds, namely zebrafinch and Japanese quail, the deslorelin implant is suitable to reduce testosterone levels. Successful treatment of hormone-dependent tumours (Sertoli-cell tumorus) in budgerigars has been described as well as the modulation of specific behavior in turkeys and an efficacy in facilitating their keeping (i. e. reduction of aggression). In reptiles, only the successful use of deslorelin in iguana has been demonstrated to date.

Lateral Body Wall Herniation Involving the Oviduct in Two Psittacine Birds

Lateral body wall herniation with involvement of the oviduct was diagnosed in a female nanday conure (Aratinga nenday) and a female eclectus parrot (Eclectus roratus). A history of chronic egg laying and chronic reproductive activity was reported in both cases. A subcutaneous mass in the area of the caudal left lateral body wall was present in both birds. Diagnostic imaging (ultrasonography, computed tomography) and cytologic examination lead to the diagnosis of left lateral body wall herniation with involvement of the oviduct. In the conure, a developing egg was contained within the herniated oviduct. Both cases were successfully treated by salpingohysterectomy and surgical correction of the hernal ring. Lateral body wall herniation with oviductal involvement in birds has not previously been reported and should be considered as a differential for birds presenting with masses originating from the lateral body wall.

Influence of a Sustained Release Deslorelin Acetate Implant on Reproductive Physiology and Associated Traits in Laying Hens

The aim of this study was to develop an animal model with non-laying hens which would allow for investigation of the relationship between egg production and common diseases in hens. A total of 40 Lohmann Selected Leghorn hens were kept for 20 weeks in a floor housing system in two groups: group "Adult" (21 weeks of age) and group "Juvenile" (14 weeks of age). In each group, 10 hens were administered a 4.7 mg sustained release deslorelin acetate implant subcutaneously; in group "Adult" after, in group "Juvenile" before the onset of lay. In both groups, the remaining hens served as control hens. An examination of each hen was performed weekly, including ultrasonography to check for ovarian follicles, analysis of estradiol-17ß plasma concentration, and assessment of comb size. Digital radiographs of the keel bone were taken in experimental weeks 7 and 15. No follicles were detected on the ovary of treated hens for a certain time period which varied between individuals (between 8 weeks and until the end of the experiment). Estradiol-17ß concentrations were significantly higher in control hens. The comb was significantly smaller in treated hens. A lower prevalence of keel bone damage (group "Adult") and foot pad dermatitis (FPD) (both groups) was found in treated compared to control hens. These results show that a model with laying and non-laying hens can be achieved by administering a deslorelin acetate implant. Furthermore, they indicate a relationship between egg production and keel bone damage as well as FPD.

Gonadotrophin-Releasing Hormone Agonists and Other Contraceptive Medications in Exotic Companion Animals

The use of a gonadotrophin-releasing hormone agonist slow-release implant (GnRH A-SRI) has become increasingly popular as an alternative for surgical contraception in many species. Although these implants have proven to be very effective in some species (eg, ferrets, rats, chicken, psittacines, and iguanas), they have been found less effective in other species (eg, male guinea pigs and rabbits, veiled chameleons, slider turtles, and leopard geckos). This review provides an overview of the available literature on the effects of GnRH A-SRIs in companion exotic animals.

Medication for Behavior Modification in Birds

The use of behavior modifying drugs may be considered in birds with behavior problems, especially those refractory to behavior modification therapy and environmental management. To accomplish behavior change, a variety of drugs can be used, including psychoactive drugs, hormones, antihistamines, analgesics, and anticonvulsants. Because their prescription to birds is off-label, these drugs are considered appropriate only when a sound rationale can be provided for their use. This requires a (correct) behavioral diagnosis to be established. In addition, regular monitoring and follow-up are warranted to determine the efficacy of the treatment and evaluate the occurrence of potential adverse side effects.

Overview of Drug Delivery Methods in Exotics, Including Their Anatomic and Physiologic Considerations

Drug delivery to exotic animals may be extrapolated from domestic animals, but some physiologic and anatomic differences complicate treatment administration. Knowing these differences enables one to choose optimal routes for drug delivery. This review provides practitioners with a detailed review of the currently reported methods used for drug delivery of various medications in the most common exotic animal species. Exotic animal peculiarities that are relevant for drug administration are discussed in the text and outlined in tables and boxes to help the reader easily find targeted information.

Validation of 2 point-of-care meters for measuring triglycerides in chickens using whole blood and plasma

Disorders of the avian reproductive tract are common, yet monitoring their resolution presents a diagnostic dilemma. Reproductive hormones such as luteinizing hormone or estrogen are the best reflection of reproductive status, but the required sample volumes and lack of reference intervals limit their clinical utility. An alternative analyte is blood triglyceride, the concentration of which rises markedly during sustained estrogen release from the ovary. Portable meters for measuring human blood triglyceride concentration offer the advantage of using minimal sample volumes, but these have not been validated for use in birds. We assessed the precision and accuracy of 2 portable meters for measuring blood triglyceride concentration in pooled whole blood and plasma from chickens ( n = 42), and performed method comparison using a reference analyzer and determined total error. Within-run repeatability was fair-to-excellent using whole blood and plasma (range: 2.5-11.5%), and between-run repeatability using plasma was similar (3.1-12.2%). The meters performed well in recovery and dilution studies in which almost all readings fell within the preset requirement of 75-125%. Correlations between each meter, using whole blood and plasma, and the reference analyzer, using plasma only, were high to very high (0.86-0.98). Bias determined by Bland-Altman analysis was similar between whole blood and plasma for each meter, yet markedly different between the meters. The calculated total observed error was consequently within our pre-set total allowable error of 25% for one meter but not the other, indicating the requirement for a meter-specific reference interval.

Reproductive Disorders in Parrots

Disease affecting the reproductive tract of the companion parrot is often impacted by physiologic and environmental stimuli. In conjunction with appropriate medical management, some birds diagnosed with reproductive disorders may be successfully treated. Once the bird is diagnosed with a disease condition affecting the reproductive tract, therapeutic measures are focused on stabilizing and supporting the patient, and surgical intervention is required only in the most severe cases. Hormonal therapy with synthetic, long-acting GnRH agonists should be considered for chronic reproductive disease conditions in which decreasing ovarian activity can help alleviate certain disease processes.

Reproductive Disorders in Commonly Kept Fowl

Backyard poultry and other commonly kept fowl species are often kept for their ability to lay eggs. Reproductive disease is common in fowl species. Despite being classified as food-producing species, they can be considered valuable pets, and the demand for adequate veterinary care is constantly increasing. The clinician should be familiar with the different abnormalities and the potential treatment options. Fowl species have been traditionally an anatomic, physiologic, and experimental model for avian medicine; however, information about treatment options is often limited and extrapolated from other species.

Avian Oncology: Diseases, Diagnostics, and Therapeutics

Companion birds are increasingly living longer due to improved husbandry, nutrition, and veterinary care. As a consequence, a growing number of geriatric disease conditions are diagnosed and managed by veterinarians. Awareness of bird owners of diagnostic and treatment options for neoplastic diseases in humans and domestic animals has led to increasing demand to provide advanced diagnostic and treatment modalities for companion birds diagnosed with neoplasia. Treatment remains challenging in many companion birds due to the lack of information regarding prognosis and efficacy of antineoplastic treatments in these species. There is no established standard of care for most tumors in companion birds.

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.