DETERMINATION OF FETAL SEX BY ULTRASONOGRAPHY AND PCR USING FETAL FLUID ASPIRATED BY AMNIOCENTESIS IN COWS

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Sex of the bovine fetus was predicted by ultrasonography and Y-chromosome specific DNA amplified by PCR in fetal fluid, which was aspirated by transvaginal-transuterine ultrasound-guided amniocentesis. Ultrasound examination were done in 68 cows through 117 trials between Day 35 to 93. Sex was correctly diagnosed as male in 43/46 (95.3%) and as female in 40/44 (90.9%) . Sex was not diagnosed in 27 cows. A total of 35 aspirates from 30 cows, 15 Holsteins and 15 Japanese Blacks at from 59 to 250 days of pregnancy were used. Five cows were aspirated twice at a 10 day interval. A 5.0 MHz convex array transducer connected to a scanner was inserted into the vagina under caudal epidural anesthesia. The transducer was equipped with a 65cm long, 21 gauge needle within the probe carrier. A bovine male-specific primer and a bovine gender-neutral primer were used. Fetal fluid was obtained from all except two cows in early pregnancy. Five animals aborted within one week following aspiration. A total of 33 samples, 29 of amniotic fluid and 4 of allantoic fluid, were subjected to PCR analysis. Fetal gender was identified in 31/33 samples (18 females and 13 males) . Gender was also determined by gross examination of external genitalia of offspring after calving or abortion. Fetal gender was correctly identified by PCR analysis of aspirated fetal fluid in 16/16 females and in 13/15 males. Transvaginal ultrasound-guided amniocentesis followed by PCR analysis of aspirated cell DNA can be used to accurately determine fetal sex in cows at from 70 to 100 days of pregnancy. The procedure requires considerable skill and is not without some risk to fetal viability.