The use of GnRH agonist for supression of cats reproductive function

The article presents the results concerning the duration of GnRH agonist deslorelin «Suprelorin» 4.7 mg using in cats prepubertal and pubertal age. Experiments conducted on pedigree and non-pedigree cats and lasting for 2.5 years. For research was formed three groups (n = 10), age from 3 months to 3 years. The first group was the control animals, they flowed naturally estrus cycle, they received any drugs and have no contact with male. The estrus cycle of the control group of animals observed an average six times within one year, three times in spring and autumn, which is the norm for this type of animal. For 30 months (2.5 years) observation cats from the control group showed excitement stage of estrus cycle an average 15 times. Animals from the second group, age 3–6 months, which has not have the first estrus (prepubertal) was placed subcutaneous implant «Suprelorin» 4.7 mg. In the third group were cats from 7 months to 3 years which have experienced one or more estrus cycles (pubertal). The animals were implanted implant «Suprelorin» 4.7 mg immediately after the last estrus. In the second group of animals (prepubertal), excitement stage of reproductive cycle manifested through 480–1567 days after implant implanted and the average duration of the reproductive cycle was 920 days (30 months). A few cats from this group were found changes in the reproductive system such as: uneven structure of the endometrium, reducing the size of the ovaries, ovarian cysts after ovariohysterectomy. Cats from the third group (pubertal) excitement stage of reproductive cycle manifested after 120 to 730 days after implanted the GnRH implant and the average duration of the reproductive cycle was 379 days (approximately 13 months). A few cats from this group, after ovariohysterectomy, observed changes in the reproductive system such as: endometrial hyperplasia, uneven structure and porosity consistency endometrial, ovarian cyst.


Introduction
A potent agonist of gonadotropin-releasing hormone (GnRH) deslorelin is becoming more and more common in the practice of small animals reproduction and is available in many countries. It is represented as a subcutaneous implant («Suprelorin»), which is slowly released the low dose of hormone in animal's organism a long period of time (Fontaine and Fontbonne, 2011;Walter et al., 2011).
The action of GnRH antagonists completely focused on blocking and inhibiting GnRH receptor-induced, resulting in an immediate drop in the secretion of FSH and LH. In contrast to this, GnRH agonists, GnRH receptors are activated, causing hypersecretion of circulating FSH and LH, which are accompanied by increased concentrations of sex steroid hormones, called «flare effect». But after the initial stimulation effect in excess of the dose or low long-term doses of GnRH agonists, resulting in a suppression of pituitary gonadotropin receptor regulation and suppression of LH and FSH release with subsequent suppression of reproductive function of animals (Corrada et al., 2006;Trigg et al., 2006).
GnRH agonist deslorelin («Suprelorin») has been actively used in the leading veterinary clinics Ukraine, but not sufficiently studied the duration of the implant «Suprelorin» 4.7 mg to inhibit reproductive function pubertal and prepubertal cats.

Materials and methods
Experiments conducted on pedigree and non-pedigree cats during 2.5 years. The owners of the animals that was treated in Kharkiv clinics wants to prevent unwanted displays of estrous behavior in animals by putting the implant «Suprelorin» 4.7 mg. For research was formed three groups of cats (n = 10), age from 3 months to 3 years. The first group was the control, the sexual cycle of animals flowed naturally, they receive any drugs, and had no contacts with a male.
Animals of the second group, aged 3-6 months, which have not been at the first estrus cycle (prepubertal) was implanted subcutaneous implant «Suprelorin» 4.7 mg. In the third group were cats aged from 7 months to 3 years which have one or more estrus cycles (pubertal). The animals were implanted subcutaneous implant immediately after the end of the last estrus.
After the research several animals from the second and third group was conducted ovariohysterectomy.

Results and discussion
Cat's sexual cycle of the control group experienced an average of six times within one year, three times in spring and autumn, which is the norm for this type of animal. For 30 months (2.5 years) observation cat control group showed excitement stage of estrus cycle an average of 15 times.
In the second group of animals (prepubertal), stage of sexual cycle excitement manifested through 480-1567 days after implantation of the implant and the average duration of the sexual cycle was 920 days (30 months). A few cats from that group, after the end of the implant action, were conducted ovariohysterectomy and were found in the reproductive system changes such as: an uneven structure of the endometrium, ovarian cysts and reducing the size of the ovaries.
Cats from the third group (pubertal) excitation stage of sexual cycle manifested by 120-730 days after implanted the subcutaneous implant and the average duration of estrus cycle was 379 days (approximately 13 months). A few cats from this group, after ovariohysterectomy, observed infringements in the reproductive system such as endometrial hyperplasia, uneven structure and porosity endometrium and ovarian cyst.