Causes of Equine Abortion and Birth Defects

As foaling season approaches, breeders are highly anticipating their new arrivals. Whether you are breeding your mare for the first time or operating a large breeding organization, every foaling is just as magical and exciting as the first time you witness it. But why do some mares not carry their foals to full term? Why are some foals born with abnormalities? Causes of abortion in mares can include bacterial or viral infections, hormonal imbalances in the mare, twinning and congenital abnormalities in the foal. The most common cause of viral abortion is Equine Herpes Virus (EHV). EHV has different strains that can cause different symptoms in horses, but the strain that causes abortion is EHV-1. If infected with EHV-1, mares often abort between 8 and 11 months’ gestation, although some carry to term and the foal dies shortly after birth. The good news is that there is a vaccine available…

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