and driven by oxytocin (Handler et al. 2003) or PGF2a (Kask et al. 1997)
release. As a result, many operators routinely treat mares with systemic
antibiotics pre and post-transfer to reduce the likelihood of bacterial
contamination developing into a pregnancy-threatening endometritis (e.g.
see Wilsher and Allen 2004) and/or with flunixin meglumine immediately
pre-transfer and progestagens for 2-3 weeks post-transfer to reduce the
risk of pregnancy failure due to transfer-induced PGF2a release and
luteolysis. In fact, transfer-induced disturbances in luteal function appear to
be uncommon after transcervical embryo transfer (Stout et al. 2005b) or
sham transfer (Betteridge et al. 1985; Kask et al. 1997), while cervical
dilation per se does not disrupt the progression of pregnancy (Handler et
al. 2002). Indeed, the high pregnancy rates achieved by experienced
operators in the absence of any supportive treatments (e.g. Losinno et al.
2001; Jasko 2002) suggest that they are unnecessary if the technique is
performed smoothly. Nevertheless, it remains possible that one or other of
the treatments may be helpful during the acquisition of experience; it is
equally possible that the failure of inexperienced technicians to establish
pregnancy is due to failure to deposit th