PRODUCTION OF TWIN CALVES WITH IN-VITRO FERTILIZED EMBRYOS - EFFECTS ON THE REPRODUCTIVE-PERFORMANCE OF DAIRY-COWS

Attempts were made to produce twin calves by implanting in vitro ferti lised and matured (IVF) embryos into dairy cows, Twinning rates were c onsistently at the lower end of the range reported to have been obtain ed with in vivo derived embryos, The low pregnancy rates, higher than expected early embryonic losses, and increased fetal deaths and aborti ons recorded may indicate that IVF embryos are less viable, Fetal over size in single calves was a significant problem in the first two years of the trial. The subsequent conception rates of cows that calved twi ns and those that calved singles were similar in spite of a much highe r incidence of retained placenta and an increased interval to first oe strus in the cows bearing twins.