160 DETERMINATION OF THE INCIDENCE OF EMBRYONIC MORTALITY IN SYNCHRONIZED EWES DURING THE BREEDING SEASON

Abstract

The aim of the present study was to evaluate the incidence of embryonic mortality in synchronized Konya Merino ewes (2–4 years of age) during the the breeding season. The flushing procedure started in 126 ewes, beginning 1 week before the breeding period until mating. The ewes were synchronized using progesterone : PMSG; a sponge containing 40 mg florogestone acetate was placed into vagina for 12 days. PMSG (500 IU) was given intramuscularly at the time of sponge removal and ewes were allowed to mate 48-60 hours (Day 0) after PMSG injection. The first pregnancy diagnosis was done transrectally 18 days after mating by using B-mode, linear array, 5 MHz real-time ultrasonography, and it was repeated again on Days 22, 26, 30, and 34. One hundred eleven ewes were pregnant on Day 18, and 191 embryos were detected in 111 pregnant ewes. There were 44 single, 54 twin, and 13 triple pregnancies. Embryonic death was determined in 39 out of 111 ewes (35.1%), and 45 embryos out of the total of 191 were lost (23.6%). Among the ewes which experienced embryonic death, 28 ewes maintained pregnancy while 11 ewes (9 single, 1 twin, and 1 triple pregnancy) did not. Among the embryos that were dead, 9 (20%), 20 (44.4%), and 16 (35.6%) were from single, twin, and triple pregnancies, respectively. Rates of embryonic death in the total number of embryos according to type pregnancy were 20% (9/45), 18.5% (20/108), and 41% (16/39). Incidence of embryonic deaths were 22.2% (10/45), 51.1% (23/45), 22.2% (10/45), and 4.5% (2/45) for Days 22, 26, 30, and 34, respectively. The majority of embryonic deaths were observed by Day 22 in single pregnancies and by Day 26 in multiple pregnancies. Incidence of termination of pregnancy in single pregnancies was significantly higher than for twin pregnancies (P < 0.01). The rate of embryonic mortality between single and twin pregnancies was not significant, whereas it was significant among single and triple and among twin and triple pregnancies (P < 0.05 and P < 0.01, respectively). In conclusion, incidence of embryonic death was similar between single and twin pregnancies but the majority of pregnancy losses were observed in single pregnancies. Although embryonic deaths are observed, maintenance of pregnancy conceals the problem of embryonic mortality in multiple pregnancies. Therefore, applications to improve the survival of embryos during the first month after mating could yield higher numbers of lambs.