S Soroori - Department of Surgery and Radiology
A Veshkini - Department of Surgery and Radiology
P Tajik - Department of Theriogenology, Faculty of Veterinary Medicine, University of Tehran, Tehran-Iran

To give a standard in the Iranian Chall ewes, 24 of them were synchronized by two injections ofPGF2α (12.5 mg/ewe Lutalize, Upjohn) 8 day apart. Forty-eight h after the 2nd injection, 16 ewesshowed signs of estrous and were randomly divided into 2 groups and each was introduced a fertileram for 24 h (ram introducing day was counted as day 0). Embryonic vesicle (E.V.), biparietal diameter(B.P.D.) and crown ramp length (C.R.L.) were measured. Early pregnancy diagnosis was performedby transrectal (with or without abdominal pressure) ultrasonography in standing position.Ultrasonography was performed until day 144. Embryonic vesicle was 0.55 cm in diameter on the day18. It was 0.79, 0.95, 1.41, 1.91, 2.42, 2.98 and 3.42 cm in days 20, 21, 24, 25, 30, 33 and 37 ofpregnancy, respectively. The first assessment of BPD was in day 37, which was 1.04 cm. It was 1.19,1.87, 4.12 and 6.27 for days 40, 61, 98 and 144 of pregnancy, respectively. CRL was 2.25, 2.78, 3.19,4.33, 5.39, 6.94 and 8.03 in days 33, 37, 40, 44, 47, 54 and 58 of pregnancy. These data are the firstreport giving a standard measurement in Chall gestational age assessment. J.Vet.Res. 62,2:1-5,2007.

ultrsonography, sheep, pregnancy