How to prevent retained placenta in domestic animals

Retention of fetal membranes| Retained Placenta

Also abbreviated as RFM (retention of fetal membranes) /ROP.

Retention of fetal membranes in Cows 

Retained placenta

Retention of fetal membranes, or retained placenta, usually is defined as failure to expel fetal membranes within 24 hr after parturition. Normally, expulsion occurs within 3–8 hr after calf delivery. The incidence in healthy dairy cows is 5%–15%, whereas the incidence in beef cows is lower. The incidence is increased by abortion (particularly with brucellosis or mycotic abortion), dystocia, twin birth, stillbirth, hypocalcemia, high environmental temperature, advancing age of the cow, premature birth or induction of parturition, placentitis, and nutritional disturbances. Cows with retained fetal membranes are at increased risk of metritis, displaced abomasum, and mastitis.

Retention of fetal membranes is mediated by impaired migration of neutrophils to the placental interface in the periparturient period. The impaired neutrophil function extends into the postpartum period and probably mediates the recognized complications of retained fetal membranes. Cows with retained fetal membranes have increased cortisol and decreased estradiol concentrations in late pregnancy. They may also have an altered prostaglandin (PG) E2:PGF2 ratio. Uterine contractility is increased in affected cows. (Placental detachment, rather than uterine motility, is responsible for retention of fetal membranes.)

Diagnosis is usually straightforward as degenerating, discolored, ultimately fetid membranes are seen hanging from the vulva >24 hr after parturition. Occasionally, the retained membranes may remain within the uterus and not be readily apparent, in which case their presence may be signalled by a foul-smelling discharge. In most cases, there are no signs of systemic illness. When systemic signs are seen, they are related to toxemia. Uncomplicated retention of fetal membranes is unsightly and inconvenient for animal handlers and milkers but generally not directly harmful to the cow. However, cows with retained fetal membranes are at increased risk of developing metritis, ketosis, mastitis, and even abortion in a subsequent pregnancy. Cows that have once had retained fetal membranes are at increased risk of recurrence at a subsequent parturition.

Manual removal of the retained membranes is not recommended and is potentially harmful. Trimming of excess tissue that is objectionable to animal handlers and contributes to gross contamination of the genital tract is permissible. Untreated cows expel the membranes in 

2–11 days. Routine use of intrauterine antimicrobials has not been found to be beneficial and may be detrimental. Although advocated at various times, oxytocin, estradiol, PGF2α, and oral calcium preparations have not been shown to hasten expulsion of retained membranes or to prevent complications. When systemic signs of illness are present, systemic treatment with antimicrobials is indicated. In herds in which incidence of retained fetal membranes is unacceptably high, predisposing causes should be sought and eliminated. Supplementation with vitamin E and selenium for herds in which these nutrients are deficient has been found to be beneficial.

Retained Fetal Membranes in Mares

Equine fetal membranes are normally expelled within 3 hr after parturition, but expulsion may be delayed for 8–12 hr or even longer without signs of illness. The cause of retention of fetal membranes often is not known, but the condition is associated with infection, abortion, short or prolonged gestation, uterine atony, and dystocia. Mares that have retained their fetal membranes appear to be at increased risk of recurrence of the condition, and Friesian mares are particularly predisposed. Retention of just a portion of the fetal membranes entirely within the uterus (usually at the tip of the previously nongravid uterine horn) is less conspicuous but equally likely to result in complications. For this reason, the chorionic surface of the expelled membranes should be examined carefully to ensure they have been completely expelled.

Retention of fetal membranes may mediate development of metritis or even peritonitis. Laminitis is a potential sequela. For these reasons, it is common practice to administer oxytocin (5 U, IM, every 2–3 hr) beginning 3–4 hr after parturition if the membranes have not yet been expelled. Calcium supplementation may be beneficial. Manual removal of retained membranes carries the risk of uterine damage or prolapse and is not recommended beyond gentle tugging to displace already loosened membranes. In cases of prolonged retention of fetal membranes, antimicrobials should be administered prophylactically, along with other therapeutic strategies aimed at preventing laminitis. Mares that have recovered from retention of fetal membranes do not generally have lower fertility.

Retained Fetal Membranes in Does, Ewes, and Sows

In does and ewes, the incidence of retained fetal membranes increases with larger litter sizes and with assisted parturition. Systemic treatment to guard against infection and gentle traction on exposed membranes may be used. In sows, retained placentae are contained within the uterus and are not visible at the vulva. In this species, entire fetuses may be retained. Usually, the fetus or membranes decompose in situ. This may be accompanied by signs of systemic illness and a purulent vaginal discharge. Although serious or fatal sequelae occasionally occur, the prognosis for recovery and future fertility is surprisingly good. Antimicrobial treatment is indicated in animals with systemic signs of illness.

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