Production and development of calves from sexed-bisected bovine embryos.

Sixty-five chromosomal preparations from bisected bovine embryos were examined and 43 embryos (66.2%) with metaphase plates were observed; however, only 25 embryos (38.5%) were sexed. Fifteen of the bisected embryos sexed by chromosomal analysis were transferred to each of the 15 recipients, and 5 recipients became pregnant. Female calves were born on December 28, 1985, August 2, 1986 and July 18, 1988. The first female calf born from a sexed-bisected embryo (December 28, 1985) was the first case in Japan. The gestation lengths and birth weights of these calves were 277, 278 and 274 days, and 42.0, 44.0 and 37.0 kg, respectively. These two calves grew within the range of the "Standard developmental growth curve of the Holstein heifer" of the Japanese Holstein Association. The milk yield from 2 sexed-bisected cows were recorded. In the first cow (Case 1), she produced 8,575 kg of milk, 5.0% fat and 9.4% solids-non-fat (SNF) per year. In the other cow (Case 2), her expected milk volume was 7,800 kg per year. Confirmation of parentage was done by blood typing, and certified by the Japanese Livestock Animal Improvement Association.