ABSTRACT
Repeatabilities of total numbers of ova (TO) and morphologically normal embryos (MNE) recovered following superovulation of Brangus cows were estimated from records of 210 attempts involving 75 cows. Repeatability of the number of TO recovered was 0.22 +/- 0.08 and the number of MNE recovered was 0.19 +/- 0.08. Overall mean numbers of TO and MNE were 9.0 and 5.0, respectively. The mean numbers of TO recovered were 8.9 from the first treatment, 9.5 from the second treatment, and 8.6 from the third treatment. The mean numbers of MNE recovered were 5.2 from the first treatment, 4.6 from the second treatment, and 5.2 from the third treatment. Regressions of TO or MNE numbers per collection indicated that the superovulatory response did not decline significantly with repeated superovulation.
ABSTRACT
Mature Brangus donor cows were superovulated with follicle stim-ulating hormone administered twice daily in intramuscular injections. On day 6.5 to 7 post-estrus, embryos were collected non-surgically using a phosphate-buffered saline medium. A total of 37 ova was collected, of which 28 were advanced morulae and early blastocysts. Twenty of these embryos were selected for micromanipulation with a radial-type Leitz micromanipulator. While the embryos were in a holding medium containing 10% fetal calf serum, three glass microinstruments were used to open the zona pellucida, remove the mass of blastomeres and bisect the embryo on a vertical plane. Halved embryos were inserted into bovine zonae and placed either as single half-embryos or twin half-embryos in 0.25 ml French straws with fresh holding medium. The micromanipulated embryos (demi-embryos) were then non-surgically transplanted, either as a single demi-embryo or as a twin demi-embryo pair, into the uterine horn of day 6.5 to 8 recipient beef females ipsilateral to the existing corpus luteum. Of the 14 micromanipulated embryos that were transplanted to recipients, pregnancy rates were 16.6% for the single demi-embryos and 62.5% for the twin demi-embryos. No pregnancies resulted from bisected blastocysts.
