Cervical timed artificial insemination in ewes

Syncronization protocols with short, mid and long intervals between prostaglandin doses: Doctoral thesis abstract

Abstract

The aim of this work was to generate information on protocols to synchronise estrous and ovulation using prostaglandin (PG), where the injections were administered at short (7 or 10 days), mid (12 or 13 days) or long intervals (14, 15 or 16 days). To assess its use for cervical timed artificial insemination (TAI) with fresh semen they were compared to a progestagen-eCG based protocol (P4-eCG). The hypothesis was that longer intervals (days) between PG injections will determine differences in estrus response, ovarian follicular growth and progesterone and estradiol plasma concentrations, improving the reproductive outcome due to an adequate hormonal milieu, resulting in reproductive results comparable with a P4-eCG protocol. Four experiments were performed during the breeding season using 966 adult Corriedale ewes. Protocols with 10 or 12 day-intervals were associated to a higher estrous synchrony. The ovarian follicular growth, the interval PG-estrus, PG-ovulation and the ovulation rate were similar among PG protocols; however the ovulation rate was higher using the P4-eCG protocol. The administration of PG at different intervals determined differences in the duration of the luteal phase and progesterone levels that was positively correlated with plasma estradiol concentrations. Intervals of 15 and 16 days between PG injections determined greater rates of non-return to service, fertility and fecundity compared to 7, 10, 12 or 13 intervals, but similar to the P4-eCG protocol. It was concluded that under the conditions of these experiments, long intervals between PG injections (15 or 16 days) resulted in higher reproductive outcomes using cervical TAI with fresh semen, compared to short or mid intervals and similar to a P4-eCG protocol. The results obtained in this work lead to the development of a new alternative for the reproductive management of the ewe during breeding season.