Comparison of estrus response and subsequent fertility following estrus synchronization with six protocols in Ossimi ewes during the early summer season

Abstract

This study investigates the effect of estrus synchronization on the reproductive performance of Ossimi ewes during the early summer season to prove that they are cyclic throughout the year in subtropical climates. In June, 280 ewes were assigned to seven (n = 40) groups and received one of the following: 1) short-term progesterone (ST) P4 treated ewes received 20 mg P4 day after day for 6 days and 500 international unit (IU) equine chorionic gonadotropin (eCG) on day 6; 2) long-term P4 (LT) P4 treated ewes received 20 mg P4 day after day for 12 days and 500 IU eCG on day 12; 3) double prostaglandin (PG) F2α 7days apart and 500 IU eCG on day 7 (PGF2α-7d); 4) double PGF2α 14 days apart and 500 IU eCG on day 14 (PGF2α-14d); 5) traditional ovulation synchronization (T-Ovsynch; gonadotropin-releasing hormone (GnRH)-0 day; PGF2α-5 day and GnRH-7 day); 6) non-traditional ovulation synchronization (NT-Ovsynch; GnRH-0 day; PGF2α-7 day and GnRH-9 day); 7) control ewes received no treatment. There were significant differences among groups for estrus rate, the onset of estrus, pregnancy, and lambing rates as well as prolificacy and gestation period. The highest (90 %) estrus rate was recorded in (LT) P4, PGF2α-14d, and NT-Ovsynch protocols while the lambing rate was the maximum (100 %) in PGF2α-14d. Although all treatments had a positive effect on ewe fertility; long-term protocols particularly PGF2α-14d; are recommended to improve Ossimi ewe fertility during the early summer season.