Evaluación de la respuesta estral, fertilidad y prolificidad de un protocolo de pre-sincronización de celo con dos dosis de análogo de prostaglandina F2α en diferentes genotipos ovinos

The aim of this work was to evaluate the reproductive performance of maternal breeds Corriedale (C), Corriedale Pro (CP), Highlander (H) and Merino Dohne (MD), as a response to a protocol of pre-synchronization of estrus with a synthetic analog of prostaglandin (PG). A total of 255 multiparous and nulliparous ewes between 2 and 6 years of age were used. These had an avergae body condition score of 3.6. The experiment was carried out during the reproductive season and ewes were managed on natural and sown pastures throughout the period. The pre-synchronization was carried out using a double PG doses protocol separated by 7 days. Artificial insemination was then performed in visible heat using marker and androgenized wethers. Ewes were inseminated cervically with fresh semen diluted with 1 ml diluent/1 ml semen. The variables analyzed were: estrus dispersion, fertility, prolificacy and fecundity of the total number of synchronized ewes. Oestrus detection to evaluate their dispersion, was carried out 16 days after the second dose of PG and for 7 days. Fertility and prolificacy were measured 85 days after the application of the second dose of PG by transrectal ultrasonography.For the statistical analysis a generalized linear model was fitted useing the SAS OnDemand software. Significant differences were obtained between breeds in terms of oestrus dispersion, and the breeds could be grouped into two groups. Corriedale and Highlander on the one hand, and Merino Dohne and Corriedale PRO on the other, with the latter two showing the lowest dispersion. No significant differences in first mating fertility were observed between MD, H and CP, but there are significant differences between C and CP. Regarding the fertility of the two matings (insemination and rebreeding), the differences between breeds disappear.Significant differences in prolificacy at both first and total mating were observed between H and C, with H having the highest prolificacy and C the lowest. MD and CP did not show significant differences with any of the breeds. Fecundity in CP and H was higher than in C, but without significant differences with MD. We can conclude that pre-synchronization treatment with double dose of PG has different effects on oestrus concentration in the different breeds studied, but in any case the period of oestrus expression is shorter compared to ewes without pre-synchronized.The use of this protocol can be a good alternative to be applied by farmers as it facilitates insemination and flock management, achieving shorter insemination and lambing periods.