PRELIMINARY INVESTIGATIONS OF THE EFFECT OF DIFFERENT DOSES GNRH (GONODDOTROPHIN RELEAZING HORMON) AND BOVINE LH (LISTERIZING HORMON) ON PLASMA LH AND TESTOSTERONE CONCENTRATIONS IN MALE DOGS = PENELITIAN PENDAHULUAN PEN

Enam ekor anjing jantan dewasa dibagi rata secara acak menjadi dua kelompok yang sama Kelompok 1, anjing diinjeksi secara intravena dengan dosis (CmRH) dan respon terhadap testosteron dan dosis (LH) diukur setiap interval 10 menit. Kelompok 2, anjing diinjeksi secara intravena dengan LH sapi dan respon terhadap testosteron diukur dengan interval yang sama seperti pada kelompok I: injeksi tunggal GnRH secara intravena menyebablcan peningkatan konsentrasi plasma testosteron dan LH pada semna dosis yang diuji, sedangkan dosis LH sapi 0.2 pg/kg dan 0.5 fig/kg dapat digunakan secara efektif untuk meningkatkan konsentrasi testosteron pada anijng jantan. Dari penelitian ini dapat disimpulkan bahwa uji tantangan dengan LH sapi dan GnRH dapat digtmakan untuk mengukur sensitifitas pituitari pada anjing jantan. Kota kunci: LH, GnRH, testosteron dan pituitar

Motility of the reticulum and rumen of sheep given juice-extracted pasture

1. Sheep were fed on different diets of juice-extracted herbage to determine what effect juice-extraction had on reticulo-rumen motility. 2. The frequency of A and B sequences of contraction of the reticulo-rumen were recorded during eating, rumination and inactivity for continuous periods of 24–72 h by using integrated electromyograms obtained from electrodes implanted in the musculature of the reticulum and cranial dorsal rumen. 3. Animals were fed on herbage in which approximately 200 g/kg dry matter had been removed in juice extracted from ryegrass (Lolium perenne), white clover (Trifolium repens), mixed ryegrass–white clover and lucerne (Medicago saliva). 4. Over all the frequency of A sequences of contraction did not differ in animals fed on pressed herbage or the unpressed material from which it was derived, although it was slower during rumination on some of the pressed material. In contrast, the frequency of B sequences was higher on the pressed material. The frequencies of contraction of A and B sequences in animals fed on pressed herbage was related to the activity of the animals in the order eating > rumination > inactivity. 5. Changes in reticulo-rumen motility due to juice extraction were small and the frequencies of A and B sequences of contraction in sheep fed on pressed herbage were in the range encountered in ruminants consuming more conventional foods

PRELIMINARY INVESTIGATION OF THE EFFECT OF DIFFERENT DOSES GNRH (GONADDOTROPIN RELEASING HORMON ) AND BOVINE LH (LISTERING HORMON) ON PLASMA LH AND TESTOSTERON CONCENTRATION IN MALE DOGS

Six male adult dogs were randomized into 2 equal groups. Groups 1, dogs wer

PRELIMINARY INVESTIGATION OF THE EFFECT OF DIFFERENT DOSES GNRH (GONADDOTROPIN RELEASING HORMON ) AND BOVINE LH (LISTERING HORMON) ON PLASMA LH AND TESTOSTERON CONCENTRATION IN MALE DOGS

Six male adult dogs were randomized into 2 equal groups. Groups 1, dogs wer

Future control options for highly valued pest marsupial species: long-acting contraceptives

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Preliminary study of ovarian activity in fillies treated with a GnRH vaccine.

OBJECTIVE: To investigate the effects of two doses (200 and 400 mg) of a water-soluble gonadotrophin-releasing hormone vaccine on the ovarian activity of 2-year-old fillies. DESIGN: A controlled vaccination dose rate experiment. ANIMALS: Six 2-year-old Australian Stock Horse fillies were randomly allocated to three treatment groups; unvaccinated controls, those receiving 200 mg of the vaccine and those receiving 400 mg of the vaccine. RESULTS: Ovarian activity of the treated fillies was suppressed at the peak of breeding season while that of untreated controls continued normally. The control fillies displayed oestrous activity and behaviour. Suppression of ovarian activity occurred for 25 and 30 weeks in the 200 and 400 mg groups, respectively. These differences were not significant. Ovarian activity ceased 2 to 3 weeks after primary vaccination. Antibody titres were low (330) until after the booster immunisation when they rapidly peaked at 22,000 and 28,000 in the 200 mg and 400 mg groups, respectively. Plasma progesterone concentrations of the treated fillies remained below 3.18 nmol/L while GnRH was suppressed. The vaccine had no significant effect on plasma androstenedione concentrations. Recovery from the effect of the vaccine was associated with development of ovarian follicles, normal oestrous behaviour and ovulation. Three of the four treated fillies and one of the controls conceived during the next breeding season and foaled normally. All the treated fillies conceived and produced normal foals in the following two breeding seasons. CONCLUSION: Both dose rates suppressed ovarian function and prevented oestrous behaviour. These effects were reversible and the subsequent fertility of the vaccinated fillies was normal

Morphological Study of the Effects of the GnRH Superagonist Deslorelin on the Canine Testis and Prostate Gland

Contents The present study is part of a programme of research designed to evaluate the efficacy of the GnRH superagonist, deslorelin (d-Trp 6-Pro 9-des-Gly 10-LHRH ethylamide), as a contraceptive for male dogs. Adult dogs were assigned to a completely randomized design comprising six groups of four animals. Each dog in the control group received a blank implant (placebo) and each dog in the other five groups received a 6 mg deslorelin implant. One group of deslorelin-treated dogs was sacrificed on each of days 16, 26, 41, 101 and 620, and testicular and prostate tissues were collected for study by light and electron microscopy. On days 16 and 26 after implantation, we observed partial disruption of the seminiferous tubules, with early spermatids shed into the lumen. On days 41 and 101 after implantation, 90-100% of the seminiferous tubules were atrophic and aspermatogenic. On day 101 after implantation, 99% of all sections showed atrophy of the epithelium and shrinkage of epithelial height in the ductus epididymides. On days 41 and 101 after implantation, prostate tissue showed complete atrophy of the glandular epithelium (100% of sections) and an apparent increase in the relative proportion of connective tissue. At the electron microscopic level, in dogs treated with deslorelin for 41 and 101 days, the Sertoli cells were smaller and their nucleoli appeared smaller than in the control dogs. The nucleoli of the Leydig cells were atrophied and prostate glandular epithelium showed reduced epithelial height, atrophy of the nucleolus and an absence of secretory granules. Tissues collected during the recovery phase revealed a complete recovery of spermatogenesis. In conclusion, slow-release implants containing deslorelin induce a striking atrophy of the testes and prostate gland by 26 days after implantation, explaining the previously reported loss of ejaculate and arrest of sperm output. At histological level, the entire process appears to be completely reversible, in accordance with data on endocrine variables and semen production

Immunocastration of colts and immunospeying of fillies

A series of experiments using an ovalbumin conjugated gonadotrophin releasing hormone was used to stimulate antibody production, suppress testosterone secretion and depress testicular function in yearling and 2 year old colts and fillies. In the preliminary experiment, an injectable oil-based formulation was administered to yearling colts. Testicular development and testosterone secretion were retarded for a period of approximately 28-32 weeks while antibody titres were greater than 1:1000. An implant and water-soluble vaccine (200 and 400 mg) is presently being tested in 2 year old colts. Testicular dimensions and testosterone concentrations decreased following vaccination. Preliminary results indicate that the effects of the implant are reversible and last for approximately 30 weeks. The water-soluble vaccine produced effective antibodies for 10-19 weeks. Plasma testosterone of all colts was reduced to gelding levels (0.2 ng/mL) while antibody titres were greater than 1:1000. Semen evaluation, morphometric analysis and daily sperm production data indicate that the testes recovered normal function. These experiments are continuing and more definitive data on the vaccine and its reversibility will be available at their conclusion. Ovarian activity of the treated fillies (200 and 400 mg) ceased soon after vaccination. Their progesterone concentrations have remained below 1 ng/mL for 20 weeks. The untreated control fillies have continued to cycle normally as determined by ovarian ultrasonography and progesterone concentrations

Reproductive responses of cattle to GnRH agonists

The response in cattle to treatment with gonadotrophin releasing hormone (GnRH) agonist includes downregulation of GnRH receptors on gonadotrophe cells, desensitisation of the anterior pituitary gland to endogenous GnRH, and the abolition of pulsatile release of LH. In bulls, a tonic pattern of LH release is associated with increased secretion of testosterone, which persists for the duration of treatment with GnRH agonist. The mechanism for this response in bulls has not been elucidated, but clearly pulsatile release of LH is not required to stimulate the synthesis of steroidogenic enzymes that sustain elevated secretion of testosterone. In heifers, desensitisation to endogenous GnRH prevents the occurrence of the pre-ovulatory surge release of LH, thus blocking ovulation. The latter provided the opportunity to evaluate the potential of a GnRH agonist bioimplant to control fertility in heifers under extensive management. Bioimplants that contained graded amounts of GnRH agonist prevented pregnancies in heifers for periods of 3 to 12 months. Zebu crossbred heifers treated with GnRH agonist from 14 to 23 months of age failed to conceive, but showed normal conception patterns when introduced into mating herds at around 26 months of age. After treatment with GnRH agonist for 4 to 6 weeks, ovarian follicular growth in heifers is restricted to relatively small (2–4 mm) antral follicles. Suppressed follicular growth in heifers treated long-term with GnRH agonist is due to a lack of gonadotrophin support, rather than a direct action of agonist at the ovaries. This was demonstrated by the ability to induce apparently normal follicular growth and ovulation by acute treatment with FSH for 4 days, followed by an injection of LH, in heifers that had been exposed to GnRH agonist for around 6 months, and which had only small (2–4 mm) antral follicles at the start of FSH treatment. GnRH agonist bioimplants have been incorporated into new multiple ovulation and embryo transfer protocols that allow control of the time of ovulation subsequent to superstimulation of ovarian follicular growth with FSH. In these protocols, the endogenous surge release of LH is blocked by treatment with agonist and ovulation is timed by injection of exogenous LH, allowing fixed-time AI. It can be concluded from recent studies that GnRH agonist bioimplants have considerable potential for both pro-fertility and anti-fertility applications in cattle. It is likely that commercial bioimplants will be available within the next 3 to 5 years

Dose-response studies for pituitary and testicular function in male dogs treated with the GnRH superagonist, deslorelin

We tested the effect of dose of GnRH superagonist on pituitary and testicular function in a study with four groups of four male dogs. The Controls received blank implants and the other three groups received implants containing 3, 6 or 12 mg deslorelin (d-Trp 6-Pro 9-des-Gly 10-GnRH ethylamide). In all deslorelin-treated groups, there was initially an acute increase in plasma concentrations of LH and testosterone, followed by declines such that both hormones became undetectable after approximately 12 days. There was a dose-response in some of these early aspects of the hormone profiles. With respect to long-term effects of treatment, the 12-mg dose had significantly greater effects than the smaller doses for the duration of minimum testicular volume [366 ± 77, mean ± SEM (3 mg), 472 ± 74 (6 mg), and 634 ± 59 (12 mg) days], absence of ejaculate [416 ± 88 (3 mg), 476 ± 83 (6 mg), and 644 ± 67 (12 mg) days], undetectable plasma concentrations of LH and testosterone [367 ± 64 (3 mg), 419 ± 72 (6 mg), and 607 ± 69 (12 mg) days], the delay until complete recovery of LH and testosterone secretion [394 ± 65 (3 mg), 484 ± 72 (6 mg) and 668 ± 47 (12 mg) days], and the delay until testes had regrown to normal volume [408 ± 77 (3 mg), 514 ± 74 (6 mg), 676 ± 59 (12 mg) days]. The time taken to restore full ejaculates was also longest for the 12-mg dose: 716 ± 67 (12 mg) days vs 440 ± 66 (3 mg) and 538 ± 83 (6 mg) days after implantation. There was no correlation between delay to recovery of normal ejaculate quality and body mass. We conclude that the dose-response relationship with deslorelin implants is not expressed with respect to the degree of suppression of reproduction, but on the maximum duration of suppression and thus to delay until recovery