Susceptibilidad del Cuerpo Lúteo a la Prostaglandina F_2α en Alpacas Inducidas a Ovulación con Plasma Seminal y GnRH

The aim of the present study was to evaluate the susceptibility of the corpus luteum to cloprostenol sodium (synthetic analog of PGF_2α) during development of the luteal phase in alpacas after induced ovulation with seminal plasma or GnRH. Semen was collected from male alpacas using an artificial vagina and then diluted 1/1 with phosphate buffered saline (PBS), centrifuged and stored at -20 °C. Females alpacas (n=96) bearing ≥7 mm follicles in their ovaries were induced to ovulate by injecting seminal plasma (n=48) and GnRH (n=48). Animal that ovulate were randomly assigned into one of six groups: control and treated with an injection of cloprostenol sodium on days 4, 5, 6, 7 and 8 post-ovulation. Blood samples were collected to determine serum progesterone concentrations at baseline and 24 hours post-injection of cloprostenol sodium. The was no luteolytic effect of PGF_2α in animals treated on day 4 or 5, whereas animals treated on day 6, 7 or 8 were responding with effective luteolysis at 24 hours post-PGF_2α showing a reduction in size of the corpus luteum and progesterone levels close or lower than <1 ng/ml. In conclusion, corpora lutea obtained by induced ovulation using seminal plasma or GnRH are susceptible to luteolysis from day 6 onwards after stimulation of ovulation.