Bovine prolapsed uterus

Bovine prolapsed uterus refers to the abnormal positioning of the bovine uterus after calving. It is most common in dairy cattle and can occur in beef cows occasionally with hypocalcaemia. It is not as commonly seen in heifers, but occasionally can be seen in dairy heifers and most commonly Herefords.
Uterine prolapse is considered a medical emergency which puts the cow at risk of shock or death by blood loss. Factors that increase the risk of having a uterine prolapsed include: calving complications that causes injury or irritation of the external birth canal, severe straining during labour, or excessive pressure when pulling out a calf. Non-calving factors include: nutrition problems such as low blood calcium, magnesium, protein, or generally poor body conditions. 
It is common for a complete uterine prolapse where the uterine horns also come out. When this happens, the uterus will hang below the hocks of the animal. When the uterus hangs below the hocks, the cow may lie on, step on or kick the exposed tissue, which increases the risk of rupturing a major artery. The uterus can become easily infected as it bruises easily and can become covered with manure.
Causes.
Uterine prolapse occurs after calving when the cervix is open and the uterus lacks tone. It occurs most commonly hours directly after calving, but may also occur up to a week post-calving. 
When the uterine prolapse does not occur directly after calving, it can be more dangerous for the cow. It is most likely that during parturition, the uterus was slightly everted, which suggests that the prolapse did not take place until after the calf was born. In these cases, the uterus is more likely to be infected. This increases the possibility that the uterus cannot be replaced in the animal, and instead must removed.
Treatment.
When a cow suffers a uterine prolapse, there are two option of treating it: reduction or amputation. In extreme cases, the cow may have hemorrhaged and suffered intense shock and therefore will be euthanized.
When choosing as treatment, there are a few considerations to take:
If the treatment is reduction, then the placenta will be removed, the endometrium thoroughly cleaned, any lacerations fixed and placed back in the right position. If amputation is the course of action, the uterus is removed.
During treatment of a prolapsed uterus, the animal must be positioned correctly to avoid increase bloat. A bloated rumen can make it much more difficult to perform a reduction.
Prevention.
There is no way to completely prevent uterine prolapse. To reduce the risk of uterine prolapse, cows are returned to a standing position and encouraged to move around as soon as possible. This is especially important in cases where a calf is pulled to assist the mother. A cow that is returned to an upright position drops the uterus back into the abdominal cavity which straightens out the uterine horns.
Prognosis.
The prognosis is generally favorable if the cow survives having the uterus replaced, and most cows survive into the long term. 
Normally, if a prolapsed uterus is placed back into the animal correctly there are no further complications. However, there is a chance that a secondary infection can occur which can cause the cow to be slow to re-breed or even unable to be re-bred at all. Although genetics does not make a difference in the risk of prolapsing again, cows that have had a prolapse are more likely to have another compared to cow that have never encountered a prolapse.
Differential diagnosis.
Uterine prolapse can often be confused with vaginal prolapse. A vaginal prolapse is a small pink or red ball of tissue ranging from the size of a grapefruit to a soccer ball. It is expelled from the animal before calving, whereas a uterine prolapse takes place after calving. It occurs when there is an increase in pressure in the abdominal cavity during the late stages of parturition. It is more common than a uterine prolapse and can also be passed by genetics. It is quite common for a vaginal prolapse to occur in the same animal each time they calve but a uterine prolapsed is not reoccurring.
Other species.
Prolapsed uterus can occur in any species but cases are most common in dairy and beef cows and ewes. Although it can occur in any species, it is less common in sows and is rare in mares, felines and bitches and rabbits.