Efecto de la superovulación sobre la cinética folicular en ovejas de raza Katahdin y Criollas de Ecuador

Abstract

The objective of this study was to evaluate the follicular kinetics in Katahdin and Criolla sheep from Ecuador subjected to a multiple ovulation and embryo transfer protocol (MOET), through the use of intravaginal progesterone devices and intramuscular application in decreasing doses of exogenous follicle stimulant hormone (FSH). The progesterone devices caused a regression phenomenon on the follicles present in the ovaries before starting the treatment. In order to start with the superovulation protocol, the animals with follicles between 2 and 3 mm were selected. The devices acted similar to a corpus luteum; FSH enhanced the growth of several follicles from the first application in all animals until the end of the treatment. Follicular dynamics was evaluated by daily transrectal ultrasonography, with the help of a linear transducer adapted so that its manipulation can be carried out from outside the animal. On the day that the animals were in heat and after mating, blood samples were taken to evaluate blood estrogen levels, and the presence of cells corresponding to estrus was evaluated by vaginal cytology, this before mating to avoid contamination of the samples. The results were subjected to a statistical analysis called T-student. The comparison of means was performed using the TUKEY significance test with a probability of experimental error of 0.05%. Statistically, the follicular size showed significant differences between both breeds, being higher in the Katahdin breed, these animals also had a higher number of follicles, and the heat was more manifest and lasting in the sheep of this breed. Estrogen levels and the percentage of surface cells were high for both racial groups, corresponding to the presentation of heat.