Impact of Lactation Length and Exogenous Progesterone/Estradiol on Embryonic Survival in Third Parity Sows
Purdue University 1998 Swine Research Report. Approximately 30 to 50% of the ova ovulated do not result in a live piglet due to embryonic/fetal mortality during gestation in sows. Approximately 20 to 30% are lost during the first 30 days of gestation (early embryonic loss), with an additional 10 to 20% lost during the last 85 days (fetal loss) (Pope, 1994); see the figure below. The majority of early embryonic loss occurs during the period of blastocyst implantation (days 13 to 18), and this period is consequently of particular interest to researchers. Early embryonic loss is poorly understood, but a number of causes have been hypothesized. A portion of fetal loss may be due to the limited space for embryos in the uterus (crowding), and due to the limited capacity of the uterus to supply blood for nutrient exchange.