Twin pregnancy diagnosis and early embryonic loss after bilateral egg transfer in beef cattle.
A linear-array ultrasound scanner with a 5 MHz rectal transducer wasevaluated for diagnostic studies of twin pregnancy and embryonic mortality in 52 Japanese Black cattle received bilateral egg transfer. Observations for pregnancy and fetus survival were monitored every 10 days from 27 to 107 days (estrus=day 0) of gestation. Accurate twin pregnancy diagnosis could be made on day 27 of gestation. The cows with non-echogenic areas in the both uterine horns on day 27 were diagnosed as twin pregnancy, since these non-echogenic areas observed only in cows later confirmed to be pregnant of twin embryos day 37 or later. Both and single embryonic losses in twin pregnant cows were also clearly detectable by using ultrasonography. Pregnancy rate in bilaterally embryo transferred cows decreased gradually from 59.6% on day 27 to 46.2% on day 67. Twinning rate of pregnant cows was as high as 80% by day 37, but it fell down to 54.2% on days 77-107. In 25 twin pregnant cows on day 27, loss of single embryo occurred in 8 cows and loss of two embryos occurred in 4 cows by day 67. The greater part of embryonic mortality and loss of single embryo happened between 38-57 days. Furthermore, the most of these embryonic losses (85.7%) occurred in the uterine horn contralateral to the side of persistent corpus luteum.