Estrous synchronization treatments in sheep: Brief update / Atualização nos protocolos de sincronização do cio em ovinos

ABSTRACT

Fixed-time artificial insemination (FTAI) is the most effective method to increase the number offemales inseminated in a single day, eliminating the necessity of estrus detection. Usually the treatments forFTAI in sheep are based on the use of progesterone-releasing devices and equine chorionic gonadotropin (eCG)administration at device removal, with an acceptable pregnancy rate. The current information about the ovarianphysiology supports the idea of shortening the traditional progesterone exposure with intravaginal devices from14 days to 5-7 days (Short-term protocols). These protocols ensure appropriate progesterone concentrations toinduce follicular turnover and ovulation of a non-persistent follicle. One im dose of PGF2alpha is required attime of device removal with eCG administration, ovulation occurs around 60 h later and FTAI is performed at 48or 54 h by cervical or intrauterine route, respectively. Several experiments have been conducted during last yearsto adjust this new protocol. In general, reported pregnancy rate is greater -or at least similar- than traditional 14days protocols, and remaining progesterone in the silicone intravaginal devices may be enough for theirreutilization with interesting results. Several improvements on follicular dynamics, time of ovulation,pharmacological associations, insemination time, sperm dose, among others, are summarized in this review inFTAI protocols facilitate a further adoption of insemination and genetic improvement in this species.(AU)