title: Manual reduction of multiple embryos in the mare: the effect on subsequent pregnancy outcome.
abstract: To determine whether manually reduced multiple pregnancies (MPs) are at a greater risk of pregnancy loss than single pregnancy (SP) in mares, and to examine if a difference exists in the timing of pregnancy loss between manually reduced MPs and SPs, 1916 Thoroughbred mares were ultrasonically monitored every 2 days during oestrus to confirm ovulation, and up to Day 40 post-ovulation to confirm pregnancy. Ultimate pregnancy outcome was ascertained from the General Thoroughbred Stud book and classified as live foal (LF), early abortion (EA; Days 40-150), slipped foal (SF; Days 150-term), and barren (B; Time of pregnancy loss unknown). Significantly (P<0.05) more SPs failed (17.23%; 226/1312) than manually reduced MPs (13.41%; 81/604). Both SPs and MPs were at greatest risk of being lost as EA (72.16%; 127/176 and 61.67%; 37/60, respectively) compared to SF (27.84%; 49/176 and 38.33%; 23/60). There was no significant difference in the time of greatest risk of pregnancy loss between manually reduced MPs and SPs. It was concluded that owners and veterinarians can be assured that manual reduction of MPs does not increase the risk of pregnancy loss above those associated with SPs.
authors: Aberystwyth University, Institute of Biological, Environmental and Rural Sciences, Aberystwyth, Ceredigion SY23 3AL, UK. mid@aber.ac.uk
authors: M C G
authors: MC
authors: Davies Morel
authors: J R
authors: JR
authors: Newcombe
authors: M
authors: M
authors: Lauber
mesh_terms: D000034:Abortion, Veterinary / Q000209:etiology*; D000818:Animals; D010064:Embryo Implantation / Q000502:physiology; D005260:Female; D006734:Horse Diseases / Q000517:prevention & control*; D006736:Horses; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000662:veterinary*; D018607:Pregnancy Reduction, Multifetal / Q000379:methods / Q000662:veterinary*; D011270:Pregnancy, Animal; D011272:Pregnancy, Multiple; D012307:Risk Factors; D050497:Stillbirth / Q000662:veterinary