Abstract
Induction of twinning was attempted in 54 Japanese black cows and 57 Holstein heifers by ipsi-lateral transfer of a pair of fertilized fresh eggs or of two demi-embryos raised from fresh of frozen eggs.
Nineteen Japanese beef cows (35%) and 35 Holstein heifers (61%) were diagnosed as pregnant by rectal palpation at 40 to 60 days after the transfer. Two Japanese beef cows and 13 Holstein heifers gave birth to twins and 14 cows and 17 heifers gave birth to single. Consequently a total of 18 and 43 live calves was born; 113% and 143% crop with regard to a pregnant mother were obtained respec-tively. The remaining 3 cows and 5 heifers resulted in abortion. Twinning rate in Holstein heifers (43%) was higher (P<. 05) than that in Japanese beef cows (13%). Twin calves were lighter in birth weight (P<. 05) and shorter in gestation period than single birth in the two breeds.
