The placenta is the membrane that connects the fetus with the dam. The button-like structures of the placenta (cotyledons) connect with the caruncles of the uterus (Figure 1).

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It is through these unions (placentomas) that nutrients are transferred from the mother to the calf. After a normal calving, the placenta will be expelled within 30 minutes to eight hours.

If the placenta has not been released after 12 hours, the cow will have a condition known as retained placenta (RP).

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 stalls and corrals loaded with bacteria.

When the cow stands and walks, the contaminated tissue is pulled back into the uterus. A cow with RP is five to seven 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 ketosis, displaced abomasums and being culled earlier. The cost of each RP is estimated at more than $300.

Overall, the incidence of RP is 8 percent; however, it ranges from 3 percent to 40 percent across herds. If your herd has an incidence of RP above 10 percent, you should be looking closely into this problem.

On the other hand, if the incidence of RP is too low in your herd, you should ensure that postpartum checks and/or recordkeeping are being done properly.

Several factors have been associated with increased risk of RP. The most important are listed below:

• Mechanical factors: difficult birth (dystocia), twins, stillbirth, abortion
• Nutritional factors: mineral and vitamin deficiency, low levels of calcium in blood
• Management factors: stress, obesity
• Infectious diseases: Brucellosis, Leptospirosis, IBR, DVD

After a normal calving, the immune system recognizes the placenta as a foreign body and attacks it. The unions between cotyledons and caruncles are destroyed and the placenta is released.

However, when the immune system is weakened, it fails to degrade those unions and RP occurs. There are several very important factors for a good immune response that should be taken into consideration to prevent RP:

• Calcium blood levels: Check the dietary cation-anion difference (DCAD)

• Dietary minerals and vitamins: Ensure the dry cow ration is properly balanced

• Body weight loss: During close-up of the dry period, provide easy access to fresh palatable food to stimulate appetite

• Quality silages: Mold and mycotoxins impair the immune response

• Stress: Avoid situations that stress animals close to calving such as pen movements, diet changes, and noises

Treating cows immediately after calving with oxytocin, prostaglandin or calcium has shown poor results on RP prevention. However, once the cow has RP, there is something very important that you can do: prevent metritis (uterine infection).

Remember, clean and comfortable bedding is critical to ensure minimal bacterial contamination of the placenta and the uterus.

Manual removal of the placenta is not advised. Postpartum, the uterine walls are thin and fragile, and manipulation of the uterus may cause harm.

Trimming out the placenta may decrease the dirt caught by the placenta; however, the pulling force of the placenta’s weight will be lost. Retained placenta ends up in metritis in 25 to 50 percent of cases.

Metritis may require antibiotic treatment and rehydration; you should seek advice from your veterinarian to establish a metritis treatment protocol. Cows with RP normally drop the placenta within a week.

The best approach in a RP case is to watch the cow closely. It is very important to remember that if she is not sick – do not treat, and if she is sick, seek advice from your veterinarian. EL

	Noelia Silva del Rio Dairy Adviser University of California This e-mail address is being protected from spambots. You need JavaScript enabled to view it