Fetal survival rate after the surgical transfer of two bovine embryos

Production of identical twins by bisection of blastocysts in the cow

“…In the present study the risk of losing one or both embryos after unilateral transfer of the embryos (Rowson, Lawson & Moor, 1971) was avoided by transferring the 'half blastocyst pairs by the cervical route to the base of the ipsilateral horn. Newcomb, Christie & Rowson (1980) (Renard, Philippon & Ménézo, 1980) or the karyotype of one 'half while the other 'half is transferred. The occurrence of 2 female fetuses of equal weight and crown-rump size could have been due to a spatial reorganization of the inner cell mass at the time of bisection, leading to 2 inner cell masses in this 'half blastocyst or to a self division of the inner cell mass at a later stage, as has been shown by Corner (1955).…”

Spatio-specific regulation of endocrine-responsive gene transcription by periovulatory endocrine profiles in the bovine reproductive tract

“…However, regional gradients of gene expression levels, previously reported in the reproductive tract of cattle (Bauersachs et al 2005), pigs (Buhi and Alvarez 2003) and sheep (Meikle et al 1997(Meikle et al , 2001, might be highly relevant for receptivity and pregnancy success. For example, early embryo transfer work determined that when two embryos were transferred bilaterally, the greatest chances of twinning were achieved when at least one embryo was transferred to the tip of the horn relative to the CL (Newcomb et al 1980). In contrast, the lowest embryo survival was noted when embryos were transferred to the base of each horn.…”

Effect of Administration with Low-dose FSH to Recipient Cows on Embryonic Survival after Bilateral Nonsurgical Embryo Transfer.

“…Unlike pigs or ewes, transuterine migration of ova or embryos rarely occurs in cattle [27]. It has been postulated that the consequent overcrowding of two embryos within one uterine horn results in the death of one of the embryos in a high proportion of cases [28], even if embryos transferred to the uterine horn ipsilateral to the CL in cows have an increased chance of survival compared to embryos transferred to the contralateral horn [29][30][31]. Also, from the point of view of performing an accurate diagnosis of twin pregnancy, it may be that twin pregnancy established by bilateral transfer will be more diagnosticable than that by unilateral transfer [5].…”

“…Therefore, it can be concluded that each embryo bilaterally distributed to uterine horns influences the other. Furthermore, it may be postulated that mutual help from two embryos produces more efficient luteotrophic (luteostatic) and/ or antiluteolytic messages to maintain pregnancy [31,32].…”