Influences of vitamin A and gonadal steroids on beef cow embryos
Brown, Brent Scott
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The cattle embryo transfer industry has grown rapidly since the advent of nonsurgicial methods of flushing donors and transferring embryos to recipients in the early 1970's. Superovulation, which increases the number of embryos that can be recovered, has made the process commercially feasible. This practice is often accomplished by injections of follicle stimulating hormone(FSH) or pregnant mare serum gonadotropins(PMSG)(Curtis, 1991). However, the response to superovulation is extremely variable both within and between cows. A treatment which could consistently increase the number of transferable embryos, would be a significant benefit to the embryo transfer industry and to the genetic improvement of cattle. As in the male, where artificial insemination increases the number of progeny from genetically superior animals, superovulation and embryo transfer could be used to increase the number of offspring from superior females leading to faster genetic improvement. The success rate of transfer in cattle is much higher than in any other species (Curtis, 1991).