Field synchronization of Ethiopian Highland sheep for fixed time artificial insemination: improvement of conception rate with a double injection of prostaglandin at 11 days

The study investigated, for fixed time artificially inseminated (AI) Menz ewes in field trials, the reproductive
performance of prostaglandin-based treatments simultaneously to the standard ‘P4+eCG’ protocol. A total
of 483 Menz ewes were assigned to either the ‘P4+eCG’ protocol, using progesterone impregnated
intravaginal sponges in combination with equine chorionic gonadotropin (eCG) injection at sponge
withdrawal, or the ‘PGFs’ treatment where sheep received a single injection of prostaglandin or ‘PGF7’
and ‘PGF11’ where ewes were synchronized with 2 injections of prostaglandin 7 or 11 days apart,
respectively. AI was implemented with fresh semen at 55 ± 1 h after the end of the hormonal
treatment. Conception rate (CR; 60.87 ± 4.2) was highest for PGF11 ewes (P < 0.05); PGFs ewes had the
lowest CR (34.07 ± 4.1). Other factors did not affect variation in CR (P > 0.05). A higher proportion of
ewes in the P4+eCG group yielded twins and triplets compared to the 3 prostaglandin-based protocols
(P < 0.01). Nevertheless, a higher (P = 0.02) proportion (17.11 ± 4.3) of PGF11 ewes yielded twins by
comparison to their PGF7 counterparts (2.50 ± 2.5). PGF-based protocol with 2 injections 11 days apart,
preceded by a careful selection of non-pregnant ewes for cervical fixed-time AI, is a feasible
reproductive management for sheep breeding programmes in Ethiopia.