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Ovulation and embryonic survival in pubertal gilts treated with gonadotropin releasing hormone. Effect of a GnRH analogue Maprelin on the reproductive performance of gilts and sows. Canine estrus induction using deslorelin Ovuplant. J Reprod Fert Suppl. Clinical Pathology. All bitches came in heat 4. J Reprod Fertil Suppl.
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In bitches, megestrol prevents estrus if given at 2. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. The presumptive basis of this Dogs gonadorelin ovulation induction in pituitary hormone secretion is an increase in the pulse frequency and possibly pulse magnitude of the GnRH released by the hypothalamic GnRH-secreting neurons and possible changes in the sensitivity of the pituitary to GnRH. It mainly possesses Goandorelin activity; therefore, gonadorflin serves as a substitute for LH to promote follicle maturation, ovulation, and formation of corpus Dogs gonadorelin ovulation induction. Suppression of estrus with prolonged use have rendered them useful for estrus Upskirt diaries in bitches.
Scott Bailey, and John Gadsby.
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- A gonadotropin-releasing hormone agonist GnRH agonist is a type of medication which affects gonadotropins and sex hormones.
A number of methods to induce estrus in dogs have been reported. Most are probably not appropriate for application in healthy, normally cycling bitches, despite interest in shortening and synchronizing cycles for purposes of accommodating owners schedules, the availability of stud dogs, or the shipments of chilled or frozen semen, or for purposes of increasing the number, frequency or size of litters in such animals. All of the methods reported, when assessed in repeated or large studies have a significant failure rate and involve one or more of the following drawbacks: smaller than normal litters in a significant percentage of successful attempts; disruption and possible prolongation of the normal cycle; and, theoretically a possibly increased risk of reproductive tract disease due to premature and possibly excessive stimulation of the reproductive tract by the administered hormones or changes in endogenous hormones provoked by the treatment.
Furthermore, some of the current methods would appear to have significant merit for application in cases of prolonged anestrus and for enhancing fertility of research bitches in colonies of dogs maintained Kate nude playground threads animal-models of heritable or genetically-based diseases of interest in human or veterinary medicine.
Variable Responses. Normal Cycles. The basic endocrinology of the normal ovarian cycle in dogs involves the following observed changes in peripheral concentrations of hormones and accompanying clinical changes. During anestrus, progesterone concentrations decline to their lowest values, typically well below 0. Proestrus Onset.
The normal stimuli for the initiation of proestrus and the associated sequence of changes in hypothalamic, pituitary and ovarian activity are not fully understood.
However, shortly before the onset of proestrus there is an increase in the frequency of pulsatile elevations in LH and often Re lump foof of mouth those of FSH, with pulse intervals of h or less, and a resulting large increase in the mean LH concentration that in terms of percentage increase is far greater than any corresponding increases in mean FSH.
The presumptive basis of this change in pituitary hormone secretion is an increase in the pulse frequency and possibly pulse magnitude of the GnRH released by the hypothalamic GnRH-secreting neurons and possible changes in the sensitivity of the pituitary to GnRH. Part of the mechanism involved appears to involve increased activity hypothalamic dopaminergic neurons or increased responsiveness of dopamine-sensitive cells, and possible inhibitory effects of prolactin, because the administration of prolactin-lowering doses of a dopamine agonist can often result in the premature initiation of the next ovarian cycle.
The increased LH along with FSH acts to stimulate a cohort of follicles to develop into estrogen-secreting proestrus follicles. Proestrus and Estrus. This may be the time of the often abrupt transition from proestrus to estrus behavior in many bitches, although the behavioral shift can occur days earlier, or days later and may not be abrupt. Mean Double ended dildo sister of estrus behavior is 1 day after the LH surge.
Throughout most of the 5 to 20 or more days of proestrus there is a progressive increase in circulating estradiol from a cohort of Social implication of contraceptives in china developing ovarian follicles, and a progressive decline in LH and FSH concentrations as a result of the inhibitory effects of estradiol and inhibin form the ovaries on pituitary gondadotropin secretion.
Peak concentrations of estradiol in late proestrus prepare the pituitary and hypothalamus for an ensuing surge-release of LH and FSH.
This surge, i. LH and FSH are also low during estrus. Progesterone increases almost imperceptibly during mid proestrus from less than 0. Gondaotrophin Administration. The earliest studies utilized serial administrations of proestrus- inducing FSH or FSH-like gonadotropin preparations including PMSG for 10 or more days with or without later administration of an ovulation inducing dose of an LH-like hormone such as hCG. PMSG administration at doses of 20 i.
The hCG may have provided a stimulus similar to that provided by increased endogenous LH pulses during natural cycles. Another approach has been to use an LH-like hormone preparation to induce a proestrus, i. During the week prior to natural proestrus, the increase in plasma LH pulse frequency is more obvious, is of greater relative magnitude, and involves a greater percent increase in mean concentrations than any corresponding increase in FSH secretion.
Fertile estrus has also been induced by frequent injections of purified LH. Estrogen Pre-treatments. The improved efficacy of gonadotropin administration following estrogen treatments is not well documented, but could be the result of two or more known effects of estradiol. Alternatively or additionally, estrogen might act directly at the level of the ovarian follicles to stimulate antral follicle development to more advanced stages.
Estrogen Administration Alone. Some studies and clinical trials demonstrated that short term estrogen treatment alone in some bitches can produce an induced proestrus that persists and is subsequently followed immediately by a fertile estrus, without any gonadotropin administration.
The success rate is variable and appears to have be greatest in bitches that have been observed, claimed or assumed to have experienced a prolonged or persistent anestrus, or to be in late anestrus, prior to estrogen treatment.
The mechanisms involved may include one or both of those previously mentioned. The report with the greatest success rate administered the estrogen in late anestrus, i. The protocol used diethylstilbestrol, 5mg tablets, p. The increased LH pulse frequency observed prior to spontaneous proestrus has been mimicked in bitches in early or mid anestrus using the intravenous administration of relatively large doses of native GnRH 0.
The initially large LH and FSH pulses become progressively smaller during the GnRH-induced proestrus as they do in natural proestrus, and usually result in a normal proestrus base on observed changes in estradiol, vaginal cytology and external genitalia, and one which is often followed by a spontaneous LH surge and estrus onset before or immediately after the termination of days of GnRH administration.
Less frequent injections of large doses of a GnRH agonist have also been successful. Neither pulse rate nor pulsatility itself appear to be critical in provoking a positive ovarian response. In fact, constant GnRH-agonist administration for days via subcutaneous osmotic-pumps requiring only a single administration have also been observed to result in a high rates of proestrus Wachs pipe saw model d, spontaneous ovulation, and pregnancy Concannon et al, Dogs gonadorelin ovulation induction at Cornell Kutzler et al, ; Volkmann et al, have demonstrated the successful use of single subcutaneous or sub-mucosal vulval insertions of a whole or a half biodegradable capsule containing the GNRH super-agonist deslorelin, a commercial formulation marketed for ovulation-induction in estrus horses Ovuplant.
However, pregnancy maintenance and litter sizes varied among trials. Implants of the agonist leuprolide have also been successfully used. Except for the lutrelin studies Concannon, there have been no published determinations of the optimal dosage or duration for the other GnRH agonists. Dopamine Agonist Administration. Several studies have reported the use of a dopamine agonist DA administered orally at doses sufficient to lower plasma prolactin as a means to terminate anestrus either prematurely in normal bitches or therapeutically in cases of prolonged or persistent anestrus.
Whether the simultaneous reduction in prolactin is part of the mechanism of action or if the mechanism involves other or additional dopaminergic effects is not known. However, efficacy appears to depend on a dopamine responsiveness sufficient to also cause suppression of prolactin; bitches that fail to experience suppression of prolactin also fail to show a clinical proestrus response.
Two DA treatments reported to be effective have included bromocriptine Parlodel at 0. Conclusions and Caveats. Estrus induction protocols are sufficiently variable in results that they are probably not appropriate to electively terminate anestrus in normal cycling dogs because a failure is likely to cause a cycle interruption with unknown consequences and a delay in an otherwise normal ovarian cycle.
An exception may be the use of a dopamine against where treatment failure does not appear to alter unduly the underlying cycle. Likewise, their application can Leg closeups of use in research bitches in which the added expense of a long anestrus hinders or even precludes cost-effective reproductive or genetic research.
Anestrus status should be confirmed by vaginal cytology and progesterone assay. Uterine complications that are potential sequellae of estrogen or gonadotrophin treatments that can cause hyper-estrogenization appear not to be of special concern in GnRH-agonist based protocols that are geared to induce a physiologic proestrus. Additional studies are needed to determine optimal doses of readily available GnRH agonists, as well as the optimal timing and dosing and application of potentially useful commercial gonadotropins and GnRH implant formulations.
Effect of duration of PMSG treatment on induction of oestrus, pregnancy rates and the complication of hyper-estrogenism in dogs. Bouchard, G.
Oestrus induction in the bitch with the synthetic estrogen DES. Concannon, P. Biology of gonadotrophin secretion in adult and prepubertal female dogs. Effects of dose and duration of constant GnRH-agonist treatment on induction of estrus in beagle dogs. In: Abstracts Book 5th Intl. Canine Feline Reproduction, Sao Paulo, Reproduction of Dogs, Cats and Exotic Carnivores.
J Reprod Fert Suppl. LH release, estrus induction and fertile ovulations in response to pulsatile administration of GnRH in anestrous dogs. J Reprod Fert Dogs gonadorelin ovulation induction 51 Oestrus induction in the bitch with buserelin implant.
Induction of fertile estrus in bitches using a sustained-release formulation of a GnRH agonist leuprolide acetate. Theriogenology Kutzler, M. Canine estrus induction using deslorelin Ovuplant. Annual Meeting Eur. Effect of stage of anestrus on the induction of estrus by the dopamine agonist cabergoline in dogs. The use of deslorelin implants for the synchronization of estrus in diestrous bitches Abstract.
Estrus induction in normal and persistent anestrus dogs by administration of human menopausal gonadotropin HMG. Wright, P. The induction of oestrus in the bitch using daily injection of pregnant mare serum gonadotrophin.
The estrous cycles of dogs and cats are not as easily manipulated as in other species. Although onset of a particular cycle may be delayed, return to normal cycling is highly variable.
Induction of estrus is expensive, unreliable, and rarely justified; it can succeed only in normal, anestrus animals. Ovariohysterectomy is the best method to prevent estrus in the bitch and queen.
Long-term suppression of estrus in the bitch may be accomplished with mibolerone, a synthetic androgen. Common side effects are clitoral hypertrophy, vaginitis especially in prepubertal bitchesincreased activity of skin sebaceous glands, mild epiphora, and alterations in hepatic function studies.
Conception rates are reportedly normal by the second cycle after treatment. If given to pregnant bitches, the urogenital system of female puppies will have severe developmental anomalies. Mibolerone should not be given to cats. Estrus can be temporarily controlled with megestrol acetate, a synthetic progestogen.
In bitches, megestrol prevents estrus if given at 2. When used to postpone an anticipated estrus, megestrol is given at 0. Return to estrus is variable but, if timed properly, approximates the next regularly anticipated cycle.
Side effects include increased appetite, weight gain, and personality changes usually more docile. Cystic endometrial Dogs gonadorelin ovulation induction may also develop. Rarely, lactation occurs. Megestrol is not approved for use in cats in the USA, but European data indicate efficacy for estrus suppression.
Due to physiological differences (a prolonged LH surge, lasting 24–36 hours) in horses, a single dose of gonadorelin is insufficient for reliable ovulation induction, and a long-acting formulation of deslorelin is more commonly used (Ferris et al., ). Gonadorelin has also been advocated for treatment of stallions with lowered libido. A gonadotropin-releasing hormone agonist (GnRH agonist) is a type of medication which affects gonadotropins and sex hormones. They are used for a variety of indications including in fertility medicine and to lower sex hormone levels in the treatment of hormone-sensitive cancers such as prostate cancer and breast cancer, certain gynecological disorders like heavy periods and endometriosis, high Biological target: GnRH receptor. - ovulation induction Female rabbits and dogs: stimulation of ovulation and multiple pregnancy Gonadorelin (as acetate) is a synthetic gonadorelin (Gonadotropin Releasing Hormone GnRH). Physiologically and chemically it is identical to the natural gonadorelin released by the hypothalamus in mammalian species.
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In light of how different farms may value ovulation induction with fixed time AI, the selection of this technology must be practical for on-farm application and must achieve the minimum targets for fertility. Infusion of lutrelin via S. Canine estrus induction using deslorelin Ovuplant. Dog Health. In swine, synthetic GnRH and its analogs have been evaluated and when injected into gilts can induce ovulation, 76 and a surge of LH that peaks 1—10 hours later, with ovulation starting between 31 and 36 hours after injection and finishing between 35 and 39 hours. Interestingly, the chorionic gonadotropins do not reliably stimulate ovulation in the species of origin. As such, many ovulation induction protocols use follicle maturation using eCG. The protocol used diethylstilbestrol, 5mg tablets, p. Control of ovulation is practical for use with fixed time artificial insemination and should prove highly advantageous for low-dose and single-service artificial insemination and for use with frozen-thawed and sex-sorted sperm. References 1. Plasma gonadotropins and ovarian hormones during the estrous cycle in high compared to low ovulation rate gilts. The timing for induction of ovulation during the follicle phase is critical as follicle maturity changes over time, and the success of the response is determined by the stage of follicle development. Granular Cell Tumor: Thoracic Spine.
To date, there is no single approach for rapid induction of estrus that has been tested sufficiently to permit recommendation for clinical use.