Pregnancy toxaemia in cows
Over-fat pregnant cows provided with insufficient food during the last two months of pregnancy can develop the disease which is similar to pregnancy toxaemia (twin lamb disease) of sheep. Deprivation of feed in fat beef cattle causes the movement of large amounts of fat from body stores to the liver.
Fat pregnant cows, particularly those carrying twin calves, are very susceptible to pregnancy toxaemia. The disease most commonly occurs in cows that are in the last two months of pregnancy or that have just calved.
Changing the diet of pregnant beef cows from a good quality, to a poor quality diet in an attempt to reduce body weight and enhance ease of calving may result in pregnancy toxaemia.
The cause of pregnancy toxaemia
In a pregnant cow there is a large demand for glucose by the developing calf in the last few weeks before birth. There is even greater demand on a cow carrying twins.
If only low-quality fibrous diets, such as straw and stubble are available, the cow is unable to meet this demand for glucose. In attempt to correct this the cow’s body mobilises body fats in large quantities.
As a result, the fat accumulates in the liver, the liver becomes enlarged, pale yellow and fatty. Furthermore, chemicals called ketone bodies are produced contributing to the cow’s illness.
All pregnant cows are at risk
Cows of all ages are at risk. Since the problem is associated with inadequate nutrition, a significant portion a herd can be affected. First calving heifers are at greatest risk due to additional energy requirements needed for growth.
Pregnancy toxaemia affects cattle that were in reasonable body condition. Pregnant beef cows which are in thin body condition on poor pasture can become emaciated and eventually recumbent and die of starvation, but they do not develop pregnancy toxaemia.
Preventing Pregnancy toxaemia
Pregnancy toxaemia can be prevented by ensuring that beef cows are adequately nourished in the eight weeks before calving. Cows should not be over-fat during pregnancy.
Even after one or two cows are affected, further cases can be prevented by providing high quality supplementary feed.
If pregnancy toxaemia occurs, remaining cows should be sorted into groups corresponding to body condition and fed accordingly.
Detecting early Pregnancy toxaemia
The first signs are easily overlooked. Cows in the early stages stop eating and appear dull and depressed. They often isolate themselves from the rest of the herd and do not forage for feed. As the disease progresses, they eventually become unable to stand.
Some cows, particularly those closer to calving, are unsteady on their feet, maybe aggressive, restless and reluctant to enter yards or a crush. Some will even charge at moving objects.
At post-mortem the liver is enlarged, pale yellow and greasy.
Treating pregnancy toxaemia
In general, cows which continue to eat will recover if given some supportive treatment and good quality feed. Cows which stop eating will eventually die.
Veterinary treatment is aimed at restoring the energy balances in the cow. The longer treatment is delayed, the less effective it will be.
Cows that have been down for more than a day usually die. All down cows must be provided prompt appropriate treatment or euthanised if appropriate.