Induction of twinning in Holstein and Japanese black cows by ipsilateral frozen embryo transfer

Mixed-breed twin production by contralateral direct-transfer of male embryos to beef cow recipients bred to GnRH-based, fixed-time AI

“…Most male embryos are deemed surplus in the dairy industry (Shea, 1999), and therefore are relatively inexpensive. Mixed-breed twins have been successfully produced by ipsilateral (Sakakibara et al, 1996) or contralateral (Holý et al, 1981) transfer of embryos to recipients bred 6 to 8 d earlier by natural service or artificial insemination following estrus detection (Sinclair et al, 1995;Sakaguchi et al, 2002). If calves are destined for beef production, free-martinism is not an issue (Horton et al, 1980;Gregory et al, 1996).…”