Changes in serum progesteron and 17beta-estradiol concentration after application of Suprelorin (4,7 deslorelin acetate) implant for estrus induction in bitches

Abstract

Since bitches are monoestrous animals, their sexual cycle occurs much less often than other domestic animals, and their reproductive capacity is potentially less. That is why manipulations with the sexual cycle of bitches and their correction are gaining more and more interest. Estrus induction is essential to commercial breeding owners for several reasons. Understanding the processes that occur during each stage of the sexual cycle, it can be safely manipulated. There are many methods for stimulating estrus, but not all of them have found their practical application. The implant Suprelorin (4.7 mg Deslorelin), which is primarily registered for the pharmacological castration of dogs and cats, has also found its use for the induction of estrus in bitches, since at the beginning of its activities, it stimulates the secretion of gonadotropin (GnRH), which triggers the synthesis of follicle-stimulating and luteinizing pituitary hormones. This initial mechanism of action of Deslorelin implants is known as the flash effect and causes heat in almost 100 % of bitches. Despite numerous publications on the use of the implant, its impact is still being investigated. The article presents changes in progesterone and estradiol after using the Suprelorin implant for estrus induction and compares the course of an induced sexual cycle with a spontaneous one. The study was conducted on 13 sexually mature bitches, 7 of them received the Suprelorin implant no earlier than 150 days after the last estrus, and 6 of them were bitches with spontaneous estrus, which were included in the control group. The implant was removed at the beginning of estrus when the progesterone level increased above 3 ng/ml. In 6/7 females, this day fell on the 10th day after the implant was inserted, and in 1/7 – on the 9th. Ovulation occurred two days after the LH peak in all bitches from the experimental group, which corresponded to the 12th day in 6/7 bitches and the 11th day in 1/7 bitches from the introduction of the implant. The estradiol peak in the control group was observed faster than in the experimental group. It occurred on average on the 8th day (mediam 8 (7–9)) from the beginning of estrus, in one bitch on the 7th day, in three - on the 8th, and in two – on the 9th day, respectively. In the experimental group, the estradiol peak occurred on the 9th day after the implant (mediam 9 (8–9), in two bitches on the 8th, and five – on the 9th. But the obtained results indicate that in most bitches of the research group, the estradiol peak occurred one day before the LH peak (5/7) and only in 2/7 two days before the LH peak, which is typical for spontaneous estrus, so despite, that,, the peak of estradiol in the experimental group was observed later than in the control group, and ovulation itself occurred faster. Quantitatively, the level of sex hormones was higher in the experimental group, and the sexual cycle was more predictable.