Immediately before or after calving down, you notice one or more of your cows getting excited and agitated. The head and limbs muscle tremble and before long, it staggers and sit down with the neck tilted on one side. Then she lies flat on her side. If you don’t take immediate action, the next thing you notice is that the cow has collapsed and in a short time it’s dead.
This in most cases is a sign of milk fever (Parturient paresis) brought about by scarcity of calcium in the blood, technically referred to as hypocalcaemia. Almost all cases happen within three days of calving down because the cow is unable to quickly replenish the calcium in blood exhausted by excessive milk and colostrum production. High milk producers are especially at a greater risk. Cows that get milk fever days before calving down is because they cannot meet the demand for calcium for the fast growing foetus. Other risk factors can be traced to:
1. Certain cattle breeds, Jersey being more vulnerable,
2. Genetics of the individual cattle,
3. Age of the cow, the older the cow the higher the risk. Heifers are hardly ever affected.
4. Fat cows
5. Feeding management – low calcium intake, low phosphorous intake, excessive calcium intake or excessive phosphorous intake
Feeding management of dry cows is by far the most important factor because it determines the quantity and availability of calcium in blood. The last two weeks before the cow calves down is very critical. High amounts of calcium in the diet reduces the efficiency of its absorption in the intestine and slows down its mobilization from the bones. Equally low amounts of calcium in the diet causes a deficit in blood. Alkaline blood brought about by feeding green fodder creates conditions that reduces the availability of calcium in the body.
Low calcium intake especially for dry cows brought about by any of the following: Heavy maize silage feeding; feeding high moisture maize fodder; inadequate supplementation; low grain intake for dry cows or low forage and high grain feeding. Low phosphorous intake due to inadequate supplementation, with high forage-low grain diet. Excessive calcium intake caused by high legume intake by dry cows or over-supplementation with calcium, or excessive calcium intake by over-supplementation with phosphorous or excessive grain feeding.
Feeding therefore should aim to maintain the right balance of calcium and phosphorous in the diet and consequently in the blood.
During early lactation the cow can have as much calcium as possible. Legumes such as Lucerne and clovers are rich in calcium and can be fed to dry cows during this period. Concentrates such as dairy meal have very high percentages of grains. As the gestation progresses pay close attention to the fibre and grain content of the diet. Ensure that diet for dry cow rations particularly during the last two to four weeks prior to calving have grain limit to a maximum of about 0.5% to 0.8% of body weight, legumes comprise 30% to 50% of forage dry matter intake and maize silage is 50% or less of the forage dry matter intake.
Ideally, keep the cows on a low calcium diet to stimulate their calcium regulatory system by mobilizing the body stores of calcium from the bone. The cow will then be able to adjust to high calcium demand at calving by mobilizing more calcium from bone than from feed. Feeding hay a month before calving and limiting green feed has the effect of acidic blood which favors calcium mobilization from the bones and improves calcium absorption from the intestines. All these are important factors in preventing milk fever.
If you have a history of milk fever, consult with an animal nutritionist to evaluate your feeding management practices especially during the last four weeks prior to calving.
This is an emergency situation and treatment should be immediate. It is always important to have a 40% solution of calcium borogluconate at hand for such emergencies in the farm. As a farmer you can take immediate steps by injecting the solution under the skin on the neck or behind the shoulder. Don’t inject the vein because you can cause sudden death. Leave that to a qualified veterinarian. Hold up cows that are flat on the ground to prevent them from bloat.
Sometimes injecting vitamin D around the calving period can be beneficial.
Injecting calcium borogluconate just before or just after calving may also prevent milk fever but this may not last long enough and milk fever may still occur. Drenching cows with Epsom salt on the day before and then twice daily for 1 to 2 days after calving has considerably reduced the incidence of milk fever in some herds.