Abstract
The objectives of the present study were to determine the time of uterine involution and ovarian activity using ultrasound examination and progesterone assay. Weekly progesterone levels were measured starting one week postpartum until two weeks after the 1st postpartum estrus in Barbary ewes lambed during winter in AL-Bayda city, north of Libya. A total of 15 Barbary ewes were used in the present study distributed in three groups according to the month of lambing as group 1 (lambed in January), group 2 (lambed in February) and group 3 (lambed in March). Ewes were examined weekly by trans-rectal ultrasound to check involution of the uterus starting one week after lambing until complete uterine involution. Blood samples were collected from the jugular vein, and serum was separated and stored at ?20 ºC until measuring progesterone using ELISA. Results showed that uterine involution completed at day 35 postpartum in groups 1 and 2, while it occurred at day 28 in group 3. The mean progesterone level was basal (less than 1 ng/ml) for a long period and started to increase at days 119, 99 and 77 postpartum in group 1, 2 and 3, respectively. One ewe did not show estrus at all during the period of study in group 2 and there were no growing follicles on their ovaries. The obtained results indicate that, uterine involution as determined by ultrasound completed earlier in ewes lambed in March than those lambed in February or January. Also, progesterone level and ultrasound examination showed that there was no ovarian activity for a longtime after parturition indicating that reproduction in Barbary ewes tends to be seasonal in AL-Bayda city, north Libya.

Key words: Ewes, Ovarian activity, Postpartum uterine involution, Ultrasound.