ABSTRACT
Embryo collection is not often very efficient in young mares, old mares or mares with a history of subfertility or infertility. Embryo collection efficiency is low in mares early in their 2-year-old year and improves later that season. Embryo collection rates are also lower in older mares (i.e. greater than 15 years of age) due to decreased oocyte quality and age related effects on uterine health. In addition, pregnancy loss rates may be higher in recipients carrying embryos from older donor mares.
