Abstract
The aim of this study was to verify the efficacy of reusing intravaginal progesterone (P4) devices on the reproductive parameters in Santa Inês ewes. Females received intravaginal P4 devices for their first, second or third use for five days plus 300 IU eCG IM and 5mg dinoprost laterovulvar 24h before device removal. Blood was collected at different moments. Transrectal ultrasonography was performed from device removal to ovulation. Part of the ewes were submitted to artificial insemination by laparoscopy (IAL - n=55) with fresh semen, whereas the rest were bred by fertile rams (n=41). On the initial 18 h, ewes that received devices for the first time showed higher P4 concentrations (5.1±1.8 vs 3.5±1.4 vs 2.4±1.1 - P<0.05). However, after the first 48h no difference was observed among all treatments and P4 supraluteal concentrations were detected in all ewes upon device removal. Estrous response, interval from device removal to estrus, rate of ovulating animals, number of ovulations, time from device removal to ovulation and average conception rates after IAL or natural mating were similar among all 3 groups. Intravaginal progesterone devices can be used up to three times without altering reproductive parameters in Santa Inês ewes.
Highlights
World sheep production is undergoing important changes and in Latin-America
The most frequently used estrous synchronization protocols are based on the use of equine chorionic gonadotropin associated with progesterone or progestagen intravaginal devices (Amorim et al, 2008)
Regarding the duration of progestagen treatment, Viñoles et al (2001) showed that traditional progestagen treatments (12–14 days) are associated with the ovulation of aged follicles and a decrease in subsequent fertility when compared to the short-term protocols (6 days)
Summary
The research on ovine reproduction has improved both quantitatively and qualitatively since the end of the 1980 ́s (Rubianes and Ungerfeld, 2002). The Brazilian territory consists of a wide variety of latitudes (5o16’N to 33o45’S), strongly or weakly influencing ewe reproduction. Studies have indicated that in the Southeastern region, Santa Inês ewes, a Brazilian tropical breed, shows estrus throughout the year, and are considered unseasonal (Sasa et al, 2002; Coelho et al, 2006), but this still does not have clear support. Induction of synchronized estrus has often been used to optimize reproductive parameters and increase production. The most frequently used estrous synchronization protocols are based on the use of equine chorionic gonadotropin associated with progesterone or progestagen intravaginal devices (Amorim et al, 2008). Many papers were published using this method (Ungerfeld et al, 2003; Dixon et al, 2006)
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