Sandra Goericke-Pesch

Clinical efficacy of a GnRH-agonist implant containing 4.7 mg deslorelin, Suprelorin®, regarding suppression of reproductive function in tomcats

The aim of the present study was to test for the efficacy of a slow release GnRH-agonist implant (4.7 mg deslorelin, Suprelorin) in the male cat. Ten toms were implanted sc in the neck. Changes in testosterone (T) secretion, testicular size, body weight and behaviour (mounting, mating, urine marking) were monitored. T concentrations were significantly decreased (P < 0.0001) to basal levels (< 0.1 ng/mL) in 5 of 10 cats after 4 weeks and in all but one tom after 11 weeks (T < 0.1 ng/mL). In this respective tom only partial downregulation with T-values from 0.2 to 0.1 ng/mL was achieved until week 27. In weeks 28 and 32, T concentrations were below 0.1 ng/mL. Compared to pretreatment values, testicular volume was significantly decreased by about 60% in week 12 and about 73% after 36 weeks (P < 0.001). Penile spines disappeared 9.4 ± 1.0 weeks after treatment. Food intake was significantly increased during treatment period (P < 0.001). In all tomcats libido, mating behaviour and urine marking were significantly reduced (P < 0.0001) after an initial stimulation. In one tom, mating an oestrous queen on day 20 after implant administration resulted in pregnancy. Mating of another tom that had T-values between 0.1 and < 0.1 ng/mL since day 24 in week 8 revealed the presence of spermatozoa; however, this mating did not result in pregnancy. Subcutaneous implant administration was well tolerated by all tomcats without sedation or anaesthesia and no treatment related negative effects were observed. These results demonstrate the clinical efficacy of the 4.7 mg deslorelin implants (Suprelorin) in the tom inducing all castration related effects.

Reversible downregulation of endocrine and germinative testicular function (hormonal castration) in the dog with the GnRH-Agonist Azagly-Nafarelin as a removable implant “Gonazon”; a preclinical trial

Downregulation of anterior pituitary GnRH-receptors by application of a slow release GnRH-implant offers an effective and reversible alternative to surgical castration of the male dog. Aim of the present study was to test the efficacy and the underlying mechanisms of a new non-biodegradable controlled-release device implant (Gonazon((R)), Intervet, containing 18.5mg of the GnRH-agonist Azagly-Nafarelin). Eight male beagle dogs were implanted s.c. at the para-umbilical region. In four dogs implant removal was after 180 days (group 1), in the other four dogs after 365 days (group 2). Eleven weeks after implantation availability of LH was reduced (p<0.0001) by 70%. After an initial increase lasting for about 4 days, testosterone (T) and estradiol (E2) concentrations decreased (p<0.0001) to basal levels within 17.5+/-8.4 days. Size of testes was decreased by about 82% after 17 weeks, size of prostate by about 46% after 5 weeks (p<0.0001). Five to 7 weeks after implantation all dogs were aspermic. Testosterone and estradiol concentrations, together with testicular and prostatic size remained suppressed in all dogs in group 1 and one dog of group 2 until implant removal. The other three dogs of group 2 escaped from down-regulation between 223 and 324 days. Effects on the availability of LH, T, E2 and on testicular and prostatic size were fully reversible after implant removal or escape from down-regulation. In six dogs semen quality was back to pre-treatment values after about 29 weeks, however, one dog developed oligozoospermia while another one stayed azoospermic, probably due to an obstruction within the epididymal duct.

Treatment of queens in estrus and after estrus with a GnRH-agonist implant containing 4.7 mg deslorelin; hormonal response, duration of efficacy, and reversibility

Although slow release GnRH-agonist implants have been shown to effectively suppress the estrous cycle in queens, there are still several remaining questions about their use: if the probability and frequency of estrus induction because of initial stimulation is dependent on the stage of cycle when animals are treated, if all effects are reversible, and to what extent fertility is regained after the end of efficacy. The latter is of major interest to cat breeders who want temporary suppression of estrus in breeding animals. Twenty queens (14 with known fertility) were treated with a 4.7 mg deslorelin implant; hormonal changes (progesterone [P4], and estradiol [E2]) and behavioral changes with special respect to estrus signs and subsequent fertility were assessed. Group A cats (N = 10) were treated 3.2 ± 0.8 days after the beginning of estrus and estrus stopped 4.1 ± 2.5 days after treatment. Estrus induction was observed in one queen 6 days after treatment, and one queen showed estrous signs 138 and 155 days after treatment. Progesterone increased significantly after treatment in all animals until day 14, then slowly decreased reaching basal levels on day 56 without any further increase. Group B cats (N = 10) were treated 7 days after the end of estrus; nine cats had P4 > 1.5 ng/mL and basal E2, one cat (B10) had basal E2 and P4. In cat B10 estrus induction occurred after treatment, but in none of the others; however, E2 increased in all group B cats 1 day after treatment but reached pretreatment concentrations on Day 7 again and remained basal. The implant was still effective in one animal of the estrus group with a duration of efficacy >1102 days, in the others duration of efficacy varied between 483 and 1025 days. Eight queens were mated afterwards and gave birth to a healthy litter with 3.3 ± 1.5 kittens. This study proves that (1) the incidence of estrus induction-although very low-is highest after treatment in estrus or postestrus, (2) the duration of efficacy varies between 16 and 37 months, and (3) estrus suppression is reversible and animals remain fertile after the treatment effect has expired.

Evaluation of the clinical efficacy of Gonazon implants in the treatment of reproductive pathologies, behavioral problems, and suppression of reproductive function in the male dog.

Efficacy of a slow-release gonadotropin-releasing hormone (GnRH)-agonist implant (Gonazon) was assessed in 53 male dogs presented with benign prostatic hyperplasia (BPH), hypersexuality, aggressive behavior (either alone or in combination), excessive micturition, or to suppress fertility. Changes in testosterone (T) and estradiol (E2) concentrations and size of testes and prostate were monitored on Weeks 0, +8, and +26 after implantation. Additional measurements during and after this period were performed in 35 dogs. Clinical signs were assessed by the owners. All implants except one were retained throughout the study. Full downregulation of testicular function (T<0.35 nmol/L) was achieved in 46 dogs, five dogs showed partial downregulation (T = 0.36 to 0.47 nmol/L), one dog did not respond, and another one displayed a transient downregulation on Week +18. On Week +8, mean T and E2 levels were reduced by 96% and 62%, respectively, and did not further decrease. Full downregulation (T<0.35 nmol/L) lasted between 6 to >22 mo in most dogs except two. Compared with pretreatment values, mean testicular and prostatic size was reduced (P<0.00001) by 54% and 52%, respectively, on Week +8 and by 68% and 64%, respectively, on Week +26. Relative reduction of prostatic size was more marked in dogs with BPH than in healthy ones on Week +8 (P<0.05) and Week +26 (P<0.02), and clinical signs of BPH disappeared rapidly after implantation. Dogs affected with BPH were significantly older (P<0.001) than nonaffected ones (9.7 vs. 2.5 yr). Hypersexuality was more common in dogs<3 yr of age, and treatment clearly improved clinical signs. Age significantly affected the response to treatment in aggressive dogs; 75% of the cases responded with an improvement. The only minor and possibly treatment-related events observed were a short-lasting exacerbation of clinical signs of BPH (two dogs), increased weight gain (three dogs), and anxiety (three dogs) with one of these dogs developing a blunt coat. These results demonstrate the clinical efficacy and overall safety of the Gonazon implants.

Reproduction control in cats: New developments in non-surgical methods

Practical relevance Reproduction control is an area of feline medicine that is assuming increasing importance in companion animal practice. Signs of oestrus such as increased vocalisation, rolling on the ground and a very short interoestrous interval may negatively influence the relationship between cat and owner, and prompt the owner to seek a method of reproduction control. In breeding catteries, control of reproduction may be needed as part of a planned breeding programme. Clinical challenges Surgical contraception is not always the owners wish — especially when a cat may be intended for future breeding. Besides, ethical principles and animal welfare legislation in an increasing number of countries are imposing restrictions on this ‘classical approach’ to reproduction control. Progestins are routinely used as non-surgical alternatives in cases where fertility is to be preserved, but the associated risks of uterine disease, mammary tumours, fibroadenomatosis or diabetes mellitus have to be taken into account — especially in predisposed animals. Modern, effective pharmacological alternatives are available for managing oestrous suppression and unwanted pregnancy. Detailed knowledge of the physiology of the oestrous cycle in the cat is necessary to ensure that the appropriate treatment is chosen for the individual animal and its owner. Audience This article presents an update for small animal practitioners on these alternative methods; specifically, the use of slow-release GnRH agonists or melatonin implants for hormonal contraception, and the antiprogestin aglepristone for pregnancy termination. Evidence base Several studies have documented the mode of action and risk of side effects of the traditional alternative to surgical castration — treatment with progestins. Evidence underpinning the safety and efficacy of GnRH agonists and melatonin implants for suppression of fertility in queens and toms is reviewed.

Retrospective analysis of canine semen evaluations with special emphasis on the use of the hypoosmotic swelling (HOS) test and acrosomal evaluation using Spermac(

Routine semen evaluation includes volume, motility, vital staining for live-dead ratio and pathomorphology including Spermac(®) staining for evaluation of the acrosome. In recent years, depending on the species, also the hypoosmotic swelling (HOS) test has been applied routinely for evaluation of semen quality. In this respect, a significant correlation between the ability of spermatozoa to swell in HOS test and the fertilizing ability has been reported. Also for evaluation of dog semen, reference has been made to the HOS test; however, its correlation to conventional semen parameters so far is discussed controversially. In the present study, the results of 400 semen examinations from stud dogs presented at our clinic were evaluated for their correlations between conventional semen parameters (motility, live/dead ratio, pathomorphology), conventional semen parameters and age, Spermac(®) staining and HOS test, respectively. We found a significant correlation of age and sperm concentration (p < 0.01), total sperm count (p < 0.0001), percentage of progressively motile sperm (p < 0.01) and live spermatozoa (p = 0.012). Furthermore, several correlations between conventional semen parameters were identified. Percentage of sperm with normal acrosome identified by Spermac (®) staining correlated significantly with live spermatozoa (p < 0.0001) and percentage of progressively motile sperm (p < 0.01). A significant correlation was proven between curled tails in HOS test and age (p < 0.001), motility (p < 0.0001), live sperm (p < 0.0001), acrosomal status (p < 0.05), pathomorphology (p < 0.0001) and sperm concentration (p = 0.011). These results indicate that Spermac(®) staining and the HOS test are useful in improving canine semen analysis.

Prevention of pregnancy in cats using aglepristone on days 5 and 6 after mating

The aim of this study was to test for the efficacy of aglepristone treatment for prevention of early pregnancy in the cat. Eleven cats (Gr. 1) were treated with 10 mg/kg aglepristone on days 5 and 6 after mating, 17 cats (Gr. 2) were used as untreated controls. Blood samples for progesterone (P4) determination were collected from 6 cats of Gr. 1 and 9 cats of Gr. 2, respectively. Ultrasound examination on day 25 revealed no pregnancy in any of the treated cats. In both groups, P4 concentrations increased from day 5 (before treatment) to day 20 (P < 0.01). In Gr. 1, the interval between aglepristone treatment and the subsequent estrus ranged from 5-299 d [18.5 (5.2) d]. Mean interestrus interval was 205 +/- 72 d in Gr. 2. Mean duration of subsequent estrus was not different to duration of estrus before treatment in Gr. 1 and in Gr. 2, respectively. Mean time between treatment and next pregnancy was 56.4 (4.7) d, ranging from 5-325 d. Pregnancy rates after the next estrus following treatment were 64 and 82% after the first and second estrus, respectively. No major treatment-related side effects were observed. In conclusion, treatment was found to be highly effective for prevention of early pregnancy.

Basal testosterone concentrations after the application of a slow-release GnRH agonist implant are associated with a loss of response to buserelin, a short-term GnRH agonist, in the tom cat

Slow-release GnRH agonist implants are considered an effective, reversible alternative to surgical castration in male tom cats. Individual differences exist regarding the onset of efficacy and might be delayed in some animals. Single measurements of testosterone (T) might result in basal concentrations also in intact male cats. Consequently, GnRH stimulation tests are performed to measure T increase in intact animals and to differentiate castrated from intact male cats. In this study, five tom cats were treated with a 4.7-mg deslorelin implant and GnRH stimulation tests using buserelin were performed before treatment and at 4-week intervals afterward until Week 20. After the last test in Week 20 all animals were castrated. Four of five animals had basal T after 4 weeks and-in contrast to pretreatment-application of buserelin did not result in any further T increase. In one animal, T was low after implant insertion, but not basal; however, a GnRH stimulation test induced a slight increase of T in Week 8 and 16 only and no response in Weeks 4, 12, and 20. Testicular volume was significantly decreased and penile spines disappeared in all cats. Testicular histology showed mixed atrophy, but also fully elongated spermatids in three of five male cats making infertility questionable. Because of the loss of the stimulatory effect of short-term GnRH application (buserelin), it can be assumed that long-term GnRH agonists also act by some mechanisms of downregulation of pituitary GnRH receptors in the tom cat.

Status of the down-regulated canine testis using two different GNRH agonist implants in comparison with the juvenile testis

Testicular function in the dog was down-regulated using two different GNRH agonist implants, with adult and juvenile testes serving as controls. Treatment resulted in an increased percentage of the interstitial area and decreased area of Leydig cell nuclei. Expression of StAR and the steroidogenic enzymes cytochrome P450 side-chain cleavage enzyme (P450scc, CYP11A1) and cytochrome P450 17α-hydroxylase-17,20-lyase (P450c17, CYP17A1) in Leydig cells was blocked at the mRNA and protein level, showing no differences between the two agonists. Staining for androgen receptor (AR) by immunohistochemistry was positive in Sertoli, Leydig and peritubular cells and some spermatogonia, with in situ hybridization confirming expression in Sertoli cells. At the mRNA level, expression of AR was not affected; however, translation was blocked (reduced percentage of AR-positive Sertoli cells), with the number of nuclei in basal position being decreased. In the juvenile testes, mRNA expression of StAR, CYP11A1 and CYP17A1 was higher compared with the other groups but distinctly lower for the AR. At the protein level, the expression was at the limit of detection for StAR; AR-positive Sertoli cells were not detected. Our observations show that the down-regulated testis is different from the juvenile one rather resembling the testicular status in seasonal breeders out of season.

Longevity of chilled canine semen comparing different extenders

The use of chilled semen has raised increased interest due to several reasons. The present study compares 3 extenders for chilling of canine semen over a 10 days storage period. Sperm rich fractions (n = 30) were divided into three aliquots and diluted with (a) a self-made tris-egg yolk extender (TEY), (b) the commercial CaniPRO™Chill 10 (CP, Minitüb, Germany) and (c) the Uppsala Equex-2 system (UpA+B): UpA+B (n = 12) or UpA (n = 18). % of totally and progressively motile sperm using computer-assisted sperm analysis (CASA, TM, PM), % live, membrane intact spermatozoa (SYBR-14/propidium iodide), % morphologically abnormal sperm, % acrosomal changes (Spermac(®)) and % membrane intact sperm (HOS test) were examined on days 0, 1, 2, 3, 5, 7 and 10. Semen quality significantly decreased during storage with significantly lower motility and lower % of live, membrane intact spermatozoa in UpA+B diluted samples. Although quality of samples chilled with TEY, CP and UpA was similar within the first 3 days, only TEY and CP revealed good results in preserving semen quality over 10 days with significantly higher PM, CASA motility parameters and % morphologically normal sperm in CP-chilled samples (each p<0.05).