Dept. Theriogenology, Fac. Vet. Med. Comparison between two regimes for induction of fertile estrus in early postpartum ewes A Kh Abdel-Razek, A Ali, A Farrag During the last few decades, different accelerated lambing systems were applied to shorten the lambing interval in sheep (1-4). Twice-yearly lambing or three lambings in two years is the ultimate goal of such programs. As part of frequent lambing programs, lambs are often weaned much earlier than usual. From a commercial viewpoint, it would be desirable for lambs to remain on the ewes for as long as they can, to take advantage of the mother’s milk supply. Recent studies demonstrated that, the onset of postpartum ovarian cyclicity can be advanced by administration of exogenous GnRH (5). However, abnormal luteal function occurs in the majority of GnRH-treated ewes in the absence of progesterone pretreatment Pretreatment with progesterone might prevents early luteolysis of the CL The aim of the present study was to apply ultrasound examination and hormonal analysis to compare between FGA-eCG and FGA-eCG-GnRH systems for induction of postpartum estrus in long-term suckled ewes. INTRODUCTION MATERIALS and METHODS  Eighteen pluriparous ewes were synchronized to lamb in February.  All ewes lambed normally and nursed their lambs for 120 days.  Forty days postpartum the ewes were allocated into 3 equal groups.  Ewes in the first and second groups received intravaginal sponge containing 40 mg FGA inserted for 12 days. On the day of sponge removal the animals of both groups were treated intramuscularly with 600 IU eCG. Ewes of group 2 received additionally 8  g GnRH (buserelin) one day after the eCG treatment. The third group did not receive any treatment and served as a control. Vaginal Sponge (FGA) 12 days No treatment eCG 24h GnRH Group 1, n=6 RESULTS and DISCUSSION  Both FGA – eCG (group 1) and FGA – eCG – GnRH (group 2) treatment regimes induced estrus in all included ewes. Non of the control ewes (group 3) showed estrus behavior during the same period (P = 0.02).  The mean interval from treatment to estrus (48.4  4.3 vs 61.0  15.6 hrs) and the mean duration of estrus behavior (30.8  5.2 vs 22.5  3.6 hrs) did not differ significantly between groups 1 and 2, respectively.  Ovulation occurred in all ewes of group 2 and in 4/5 of group 1. Only one ewe in group 3 ovulated during the same time (P = 0.018).  The mean interval from treatment to ovulation (78.0  5.7 vs 88.4  12.6 hrs), ovulation rate (2.4  0.6 vs 1.8  0.4), mean growth rate (0.78  0.1 vs 0.39  0.1 mm/day) and mean size of the ovulatory follicles (5.35  0.2 vs 5.78  0.3 mm) did not differ significantly between groups 1 and 2, respectively.  According to ultrasonographic pregnancy diagnosis on D 28, 5/6 ewes in group 1 and 3/6 in group 2 conceived.  The mean P 4 concentration increased significantly in all ewes of group 1 and 2 from D 1 (one day after sponge removal) through D 12 (P = 0.006), then the level decreased non-significantly through D 16, to increase significantly in group 1 by D 20 ( P = 0.01), Fig 1. The mean P4 levels were significantly higher in the treated ewes (groups 1 and 2) than in the control one (group 3) from D 8 through D 20. In the same time, level was higher in group 2 than in group 1 from D 4 through D 16.  Early embryonic deaths were observed in ewes of both treated groups, Fig 2. The mean number of embryos/ewe reduced non-significantly in group 1 from 2.0  1.2 on D 28 to 1.2 on D 48. Embryo losses was also noted in group 2, where the mean number decreased from 0.8  1.3 on D 28 to 0.6  0.9 on D 48. No further fetal losses was detected after D 48. The mean numbers of born lambs were similar to the mean numbers of fetuses detected on D 48.  It could be concluded that, both FGA-eCG and FGA-eCG-GnRH programs were efficient in inducting estrus and ovulation in the early postpartum ewes.  A fertile ram was introduced to the ewes 24h after sponge removal.  The ovaries were examined with transrectal ultrasonography.  Number of the ovulatory follicles, maximum size before ovulation, and their growth rate were studied and compared.  The ewes were then examined ultrasonographically weekly until D 62 postmating to observe the possibility of embryo/fetal losses.  At birth, the number of born lambs was recorded.  Eight blood samples were collected from the jugular vein of each ewes. Serum was harvested and assayed for progesterone hormone (P 4 ) by ELISA. ٍFig 1: Serum progesterone level (mean ± SEM) in relation to the type of treatment. Group 1: FGA+eCG, Group 2: FGA+eCG+GnRH, G 3: no treatment. D1: one day after sponge removal. A:normal pregnancy D 28 after mating. B:Early embryonic death D 35, the fetal membrane floating in the fetal fluid.. C:Early embryonic death D 42, increase cloudiness of the fetal fluid D:Early embryonic death D 62, complete resorption of the fetal fluid. Fig 2: Steps of early embryonic death in one ewe (A-D) REFERENCES (1)Aboul-Naga, et al., 1992, Small Rum Res 4: (2)Wheaton, et al., 1992, J Anim Sci 70: (3) Lewis, et al., 1996, J Anim Sci 74: (4) Knights, et al., 2001, J Anim Sci 79: (5)Mitchell, et al., 2003, J Anim Reprod Sci 76:67-79.