**2.2 Will it be possible to improve the parameters of presence of estrus and pregnancy using hormones in the coming years?**

Changes or results in estrous synchronization programs have been modified over the years depending on the duration of insertion of the sponge or the device in the goat, however, the use of hormones to regulate goat reproduction has been maintained over the years [12, 13], with changes especially in the higher use of nonsteroidal hormones, such as those derived from prostaglandins, gonadotropin-releasing hormones, and hormones of follicular growth and development such as equine chorionic gonadotropin; being the most frequent use in the European community for health reasons. The use of steroid hormones such as progestogens continue to be used globally [14], but under the premise of using short protocols (5 to 7 days). In the present and in future years the use of short protocols of 5–7 days will be used more and more because it has a series of advantages compared to short protocols; these being the decrease in the presence of vaginitis in animals; in the case of CIDR devices, reuse them up to twice more with an effectiveness of up to 90% of estrous in goats. However, the health risk must be considered as it can contaminate bacteria, viruses from one animal to another.

The important thing is to be able to develop vaginal devices with a lower concentration of progesterone and avoid being reused to avoid this type of infection.

On the other hand, the use of estrous synchronization protocols in goats using nonsteroidal hormones in combination with the male effect has been developing more intensively in recent years. For example, the administration of double doses of PGF2α is recommended to synchronize estrous in cycling goats, with an interval of 10–14 days (appointment), which ensures that most does will present the mid luteal phase, when applying the second dose, and that all will respond with the behavior of estrus and ovulation (appointment). However, their response may vary depending on the insemination technique, the dose to be applied and the interval between

doses. Besides, it should be considered that only the goat that is cycling with the presence of an active luteal body, would work this protocol. Currently, the male effect is used, so that an estrus occurs, a CL is formed, and the protocol based on prostaglandins is started.

In goats, PGF2α and its analogs are effective luteolytic agents, where very small doses (1.25 mg) of PGF2α are currently required, with the corpus luteum being more sensitive compared to cows. Likewise, responses to low doses of its analogues, such as cloprostenol, have been observed; 125 μg doses have been used in goats, but even a 26 μg dose has been shown to be effective [15, 16]. As in sheep, the age of the corpus luteum and, therefore, the day of the cycle in which PGF2α is administered determines the degree of synchronization obtained and the time required for the heat to appear, the LH peak and the ovulation [17]. Several studies indicate that goats treated on day 6 of the cycle go into heat and show an LH peak much earlier than those treated on day 12 [18, 19].
