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Disease Description
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Retained Placenta is usually defined as the failure to expel foetal membranes within 24 hrs after parturition. Primary retention of the foetal membranes results from a lack of detachment from the maternal caruncles, whereas secondary retention is related to a mechanical difficulty in expelling already detached foetal membranes (e.g., uterine atony). Primary and secondary retention mechanisms can coexist. Retained placenta (RP) is also known as retained foetal membrane or retained cleansing. The placenta is the membrane that connects the foetus with the dam. The button like structures of the placenta (cotyledons), connect with the caruncles of the uterus. It is through these unions (placentomas), the nutrients are transferred from the mother to the calf and wastes excretion from the foetus to the dam (mother). The placenta also known as afterbirth is the link between the foetus and the mother when the foetus is inside the uterus. After a normal calving, the placenta will be expelled within 30 minutes to 8 hours. Separation of the membranes normally occurs after the calf is born (early separation is one cause of stillbirth).RP occurs when the calf’s side of the placenta (the foetal membranes) fails to separate from the mother’s side. Generally, expulsion of fetal membrane occurs within 3-8 hr after calving. Most cows will pass the afterbirth (placenta, cleansing or calf bed) within 6 hours of calving. Some cows take up to 24 hours. If the placenta is retained longer than this, the condition is classified as retained placenta (RP) or retained fetal membranes (RFM). Retention of fetal membranes in cattle can lead to many ill effects on animal that ultimately affect reproductive and productive performance. There are three main types of retained placenta following the vagina delivery: 1) placenta adherence (when there is failed contraction of the myometrium behind the placenta), 2) trapped placenta (a detached placenta trapped behind a closed cervix) and 3) partial accreta (when there is a small area of accreta preventing detachment) (Weeks ,2008). The hormonal processes that lead to normal placental separation are multifactorial and begin before parturition. The effects of retained afterbirth on individual cows vary from severe symptoms of fever and illness, such as ketosis, to no clinical signs at all, Longer term effects of RP are an increase in time to first service, lower first service conception rate and thus an increase in time to conception (Fourichon et al., 2000; McDougall, 2001). Retained placenta by itself is not a problem; however it may lead to uterine contamination. For example, when the cow lies down, the placenta hangs further out of her body and touches dirty inanimate surroundings loaded with bacteria. When the cow stands and walks, the contaminated tissue is pulled back into the uterus.A cow with RP is 5 to 7 times more likely to have metritis (uterine infection), and her pregnancy rate decreases by approximately 15 percent. Furthermore, cows with RP are more susceptible to suffer from ketosis, displaced abomasums and being culled earlier.
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