Retained Foetal Membranes and Metritis
Dr John Henderson MRCVS
Large Animal Product Manager, Forte Healthcare Ltd.
Retained Foetal Membranes (RFM) and Metritis are separate but related conditions of the immediate post-partum period. While RFM does not cause metritis, the two conditions share many risk factors, (such as dystocia and twinning), and the delayed uterine involution and abnormal endometrial environment seen with RFMs makes the development of metritis more likely.
Retained Foetal Membranes
RFMs are defined as retention of the placenta more than 12-24 hours after calving. Most cows pass the placenta within 6 hours. RFMs predispose to metritis, ketosis and mastitis and have a negative effect on fertility, with affected cows showing an average increase in time to conception of 6 – 12 days.
In the pregnant cow the maternal caruncles are enveloped by the foetal cotyledons (like a hand covering a closed fist). At the microscopic level interlocking villi are ‘cemented’ with collagen providing a very strong attachment between maternal and foetal tissues. Normal placental detachment after calving can be thought of as having 3 separate mechanisms:
Risk factors for RFMs include:
Treatment of RFMs
Many studies have been performed worldwide and unfortunately no real consensus on effective treatments for RFMs has been reached. In UK farms, manual removal of RFMs is still commonly requested by farmers. This procedure, whereby the vet inserts a (well gloved) hand into the birth canal to forcibly remove the attached placenta has been shown at PM examination to cause haemorrhage of the uterus leading to increased bacterial invasion of the endometrium, making clinical metritis more likely. These PM studies have also shown that placental remnants are always left behind, even when removal was thought to be complete.
The administration of antibiotics, either intra-uterine or systemic, to cows with uncomplicated RFMs (cows with no metritis/are not sick) has shown no benefit in bringing about earlier release of membranes or preventing metritis.
Prostaglandin and/or Oxytocin administration has not been shown to confer any benefit in either preventing or treating RFMs.
It would seem that in all likelihood the best course of action in RFMs is to trim off excess membranes hanging from the vulva (for milking parlour hygiene) and wait for the placental attachments to break down over the next 2 to 10 days, all the while monitoring the cow for any development of clinical metritis.
Clinical Metritis (CM) is infection of the post-partum uterus by contaminating bacteria. The post-partum uterus has a disrupted surface epithelium in contact with fluid and tissue debris making the establishment of infection by these bacteria a real risk in the 10 days following calving.
The normal cow undergoes involution of the uterus after calving which expels the birth fluids (lochia). This combined with healthy natural defences, assists in preventing the establishment of metritis. In cases of dystocia or twinning where the uterus is stretched or traumatised, uterine tone is reduced, and lochia is retained. WBC phagocytosis is also reduced in these cases. This excess fluid and reduced cellular defence system will favour the establishment of bacterial infection.
Caesarean sections predispose cows to RFMs, this cow is 24 hours post op and no sign of placenta being expelled
Contamination of the uterus will also be increased by unhygienic calving pens and poor cleanliness during assisted calvings by the farmer (or vet!!)
The bacteria most frequently isolated from cases of CM are E. coli and A. pyogenes, with F. necrophorum and Bacteroides spp also common. CM involves bacterial invasion of the endometrium, glandular tissues and muscular layer of the uterus (as opposed to endometritis where only the outermost layer is infected).
© 2009 NADIS/Richard Laven. Typical appearance of RFMs
Signs of CM consist primarily of a foetid smell emanating from a cow, sometimes with an accompanying watery or bloody discharge. The cow may carry her tail head in a raised position due to discomfort. If the infection has progressed to septicaemia or toxaemia the cow will be dull, have a decreased appetite and reduced milk yield (in dairy cows).
Treatment of CM is either intrauterine or systemic antibiotic administration. Guidelines on the rational use of antibiotics advise favouring non-critical antibiotics and using antibiotics in a targeted manner. Tetracycline is effective against anaerobic/aerobic, gram positive and gram negative bacteria. Intrauterine administration of tetracyline produces immediate therapeutic concentrations in the caruncles and endometrium and because of its relatively low absorption into the bloodstream, the therapeutic action is largely confined to the uterine lumen and endometrium. Therefore tetracycline pessaries (e.g. Utertab) which provide effective local levels of a non-critical and highly effective antibiotic, without much systemic absorption are a useful first-line treatment.
In unwell or toxic cows, where deeper layers of the uterus are infected, systemic antibiotics, fluids and other supportive treatments are indicated.
Clean gloved hand with 2g Tetracycline pessary to treat case of CM
Some practitioners have advocated the draining/flushing of the infected uterus, or the infusion of dilute iodine solution. This is not to be recommended as handling of an already friable and infected uterine wall may exacerbate the problem. Also, iodine has been shown to decrease the activity of uterine leukocytes for several days after uterine application.
This article was kindly provided by Forte Healthcare
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