There are a number of things that can go wrong during the last phase of pregnancy. Some problems can be resolved or dealt with easily, and others are more serious — and can be life threatening to the cow or fetus.
EXCESS FLUID AROUND THE FETUS
On occasion, either the amnion sac surrounding the fetus or the allantoic sac (the outer “water bag”) produce too much fluid. Extra fluid in the amnion sac is very rare (a condition called hydramnios); it occurs mainly in Dexter cattle that have “bulldog” calves — a hereditary condition which may produce extra fluid as early as the third of fourth month of gestation. More commonly, excess fluid is produced in the outer water sac. This condition, called hydroallantois, is seen in the last trimester. The fetus is often quite small for that stage of gestation. The sudden increase of fluid becomes noticeable by about six to seven months when the cow develops a huge belly. The later it happens, the better chance she’ll survive until the end of pregnancy.
The large volume of fluid puts pressure on her lungs and gut; she doesn’t have room to breathe and can’t eat much — losing weight. She may become so weak and/or impaired by her large belly that she has trouble getting up and down. If she survives, she usually needs help to calve because she is weak, her uterus may not contract properly (being so distended) and the cervix may not dilate fully.
Your vet may advise terminating the pregnancy early, to save the cow. In some cases she should be humanely slaughtered. If she is near term, your vet may do a C-section, but it must be done carefully, draining off the extra fluid slowly. If it rushes out too fast, the cow may go into shock. After the calf is removed (either by traction through the birth canal after excess fluid is drained away, or by C-section), the uterus should be checked to make sure there’s not a second calf; twins are common in cases of hydroallantois.
Sometimes the pregnant uterus rotates, putting a twist in the cervix. This occurs most often at calving (during early labour), but may happen in late gestation. The lower, larger part of the uterus is supported by the floor of the abdomen, but is prone to swinging as the cow gets up and down (as she’s kneeling on her front legs and standing with her hind legs). While the uterus is suspended in the abdominal cavity, any sudden shift due to the cow falling, being knocked by another cow, or the fetus making a quick movement, may cause the uterus to swing and turn over. Cows that fight may experience torsion.
This problem is rare in heifers. It’s seen more frequently in cows with a deep, spacious abdomen. Cows with twins seldom develop torsions, since two calves more completely fill the abdominal space and create a broader base for the uterus as it rests on the floor of the abdomen.
Some torsions may be present for days or weeks without any signs, only becoming obvious when the cow goes into labour and can’t deliver the calf. If the uterus is turned only 45 to 90 degrees it may correct itself during labour. Torsions greater than 180 degrees will obstruct the birth canal (the twist closes it off) and the calf can’t be born unless the torsion is corrected. Torsions greater than 180 degrees in late gestation may create obstruction of blood vessels, interfering with blood supply to the fetus. If it dies, the cow may show signs of abdominal pain and go into shock and die, or the fetus may mummify and the cow shows few symptoms.
On rare occasion, a cow in late pregnancy may suffer rupture in the lower abdominal wall due to a severe blow to the belly, or weakness in muscles of the abdomen. This allows the uterus to drop through, with nothing between it and the outside world but the cow’s skin and some swelling.
The problem may first be noticed as a swelling about the size of a football, then it becomes larger and the belly droops. The heavy uterus and fetus drop out of the abdomen. The cow should be put in a safe place where she won’t be jostled by other cows, and closely watched. She’ll usually have a live calf, but may need help to calve. Your vet can determine whether the hernia can be repaired after removal of the calf or if the cow should be butchered.
SWELLING UNDER THE BELLY
Some cows, especially heifers, develop edema under the belly as they approach calving, and this may be mistaken for a hernia. Swelling is due to pressure on the mammary veins by the distended uterus. Swelling may become so large that it extends forward almost to the elbow. This edema will resolve after she calves.
Sometimes in late pregnancy a cow prolapses her vagina. Some cows have a structural weakness; the vaginal tissue is not well anchored. This can be an inherited problem, passed from mother to daughter or from sire to daughter if the bull’s mother had this weakness. It’s most common in Herefords, Simmental and Charolais but occurs occasionally in all breeds. Too much fat in connective tissue around the vagina may predispose a cow to this problem; it happens more often in fat cows.
Pressure and weight of the large uterus in late pregnancy causes vaginal tissue to protrude from the vulva when the cow is lying down, especially if her hind end is downhill. Weight of the calf (and gravity) puts pressure on rear parts of the reproductive tract and it bulges through the vulva. This occurs most often during the last two months of gestation. If the cow is still several weeks away from calving when she starts prolapsing, it will get worse. Advancing pregnancy puts more pressure on vaginal tissues.
At first the bulge may be the size of an orange—a pink ball protruding from the vulva. It usually goes back in when the cow gets up and the pressure is relieved. If she starts prolapsing every time she lies down, and strains while lying there, she forces more tissue out. A heavily pregnant cow often strains when passing manure lying down, or is stimulated to strain due to the presence and irritation of the prolapse, making a small problem into a bigger one. Exposed tissue becomes dirty; manure flows over it when she defecates. This causes irritation and more straining. The ball of tissue becomes so large that it can’t go back in even when the cow gets up and walks around.
Unless it’s pushed back soon after it comes out, the prolapsed tissue becomes dirty and dried out, and may become damaged. Blood circulation to these tissues is impaired, so they become swollen and vulnerable to injury and infection. The longer the inverted tissue is outside the body, the more swelling occurs (and drying of the membranes) and the harder it is to replace. Swelling restricts the passage from the bladder; the cow may not be able to urinate until the prolapse is resolved. She may strain while trying to urinate, aggravating the problem. If she goes into labour while prolapsed, the bulge of tissue impedes the birth.
Some cows have a mild prolapse (when lying down) every time they approach calving, but it never becomes a problem. Others get worse each year. If a cow has a bigger problem the next year, and you have to put it back in and stitch it, you should cull her. Otherwise you must deal with it every year (and watch her closely until she calves, so you can take the stitches out when she goes into labour). Never keep a heifer or bull from any cow that prolapses. If you are unlucky enough to buy a bull that sires daughters with this problem, don’t keep any more heifers from him.
To replace a prolapse, restrain the cow, wash the prolapsed tissue and push it back in. Take three or four stitches across the vulva with umbilical tape (strong cotton strips), using a curved surgical needle. Emergency stitching can be done with disinfected baling twine poked through holes made in the skin with a clean, sharp pocketknife. Umbilical tape is best because it’s less apt to pull out than suture thread and less abrasive than baling twine.
Cows that ingest sharp objects with their feed are at risk for hardware disease. Action of the digestive tract tends to push a nail or piece of wire into or through the gut lining. Cows are more at risk during late pregnancy; the increasing size of the uterus puts more pressure on the digestive tract. A foreign object may have been sitting harmless in the stomach, or partially embedded in the lining, then gets pushed clear through when the gut is short on space due to the enlarging uterus. If a heavily pregnant cow becomes dull, goes off feed, or shows other signs of illness or peritonitis, hardware may be a possibility; have your vet examine her.
Heather Smith Thomas ranches with her husband Lynn near Salmon, Idaho. Contact her at 208-756-2841