Milk fever is a dangerous condition that can affect a cow’s health and productivity — and your overall dairy farm profitability. With effective dairy cow feed management, you can reduce clinical milk fever cases to below 1%, according to the University of Minnesota Extension. Read on to learn how to prevent milk fever in cows, what causes it, and the symptoms to look out for.
What Is Milk Fever in Cows
Parturient paresis, otherwise known as milk fever, is a condition in which a cow’s blood calcium drops around calving. It can cause severe symptoms of weakness and death if untreated. While most well-managed farms avoid the worst cases today, mild and subclinical milk fever are widespread and affect cow health and performance.
Milk fever can also be a gateway disease. Low blood calcium (hypocalcemia) affects muscle function, nerve signaling, rumen motility, uterine function, immune response, and feed intake. Affected cows are susceptible to retained placenta, displaced abomasum, mastitis, ketosis, metritis, and more. It’s a wide-reaching issue that’s best resolved at the nutrition/feed level before it affects your herd’s performance.
How Milk Fever Develops
Dairy cows are at a significant risk of milk fever within 72 hours of giving birth. In fact, more than 75% of cases occur within the first 24 hours.
At calving, demand for calcium rises faster than some cows can replace it. The calcium excretion can jump from 10 g/day to 30 g/day at the onset of lactation, according to MSD Veterinary Manual. This lowers blood calcium levels well below the normal range, leading to milk fever in some cows.
Some Cows and Herds Are at a Higher Risk
Milk fever most commonly occurs in high-producing cows who are entering their third or later lactations, with each subsequent lactation increasing the risk by about 9%, according to research.
Some of the factors that can increase the risk are:
- Previous cases of milk fever
- High-potassium pre-fresh diets
- High dietary phosphorus intake before calving
- Low blood magnesium
- Cows 5 years and older
- Low roughage intake
- High calcium intake before calving paired with low calcium intake after calving
Jersey and Guernsey breeds are also naturally at a higher risk.
Symptoms of Milk Fever in Cows
How milk fever appears in a cow depends on the progression stage:
- Stage 1: Loss of appetite, poor gastrointestinal motility, hypersensitivity, head bobbing, cold ears, excitability, and weight shifting. Milk fever is easy to miss at this stage because it’s short-lasting. Cows are likely to move to stage 2 without calcium treatment.
- Stage 2: Lying down in a tuck position, tachycardia, cold ears, dry nose, poor walking coordination, muscle tremors, and dullness. Stage 2 lasts anywhere from 1 to 12 hours.
- Stage 3: Inability to stand and loss of consciousness. Extreme muscle flaccidity and unresponsiveness.
How Diet Affects Milk Fever Risk
When considering milk fever risk, it’s important to understand that the pre-calving diet can either prepare a cow’s body to maintain blood calcium or interfere with the process.
When a cow’s diet supports calcium release from the bones and improves calcium absorption from the gut, her blood calcium levels are less likely to drop too low. But if the diet interferes with this calcium response, blood calcium can fall, leading to clinical or subclinical hypocalcemia.
Diet affects how well a cow releases calcium from her bones and absorbs calcium from the gut. To understand how, it’s helpful to look at the biological chain:
- At calving, calcium demand rises sharply for colostrum and milk production.
- As blood calcium begins to fall, the parathyroid gland releases the parathyroid hormone (PTH).
- PTH signals the bones to release calcium into the bloodstream. However, bones can be more or less responsive to PTH, depending on the cow’s acid-base status.
- With a slightly lower blood pH, the bone and kidney tissue response to PTH is higher. Therefore, bones release more calcium.
- PTH also helps activate vitamin D through the kidneys. This is critical to increase calcium absorption from the digestive tract.
Magnesium is also critical for the process. When magnesium status is low, a cow may respond more slowly to falling blood calcium. This can increase the risk of clinical or subclinical hypocalcemia, as noted in the Nutrient Requirements of Dairy Cattle.
The goal is to lower blood pH in a controlled way so the cow can better respond to calcium needs. That’s where a negative Dietary Cation-Anion Difference (DCAD) diet comes in.
Dietary Cation-Anion Difference (DCAD) Diet
DCAD refers to the balance between positively charged minerals (potassium and sodium) and negatively charged minerals (chloride and sulfur). Diet cation-anion details are critical for avoiding milk fever.
- Diets high in anions (chloride and sulfur) push a cow toward the acidic state and lower her blood pH, reducing the chance of a severe drop in blood calcium, as noted by the University of Wisconsin-Madison.
- Diets high in cations (potassium and sodium) do the opposite, making her body less responsive to PTH.
Urine pH can help confirm whether a negative DCAD program is working. If urine pH stays too high, the diet may not be acidifying the cow enough. If it drops too low, the cow may be over-acidified, which can reduce dry matter intake.
Milk Fever Prevention Through Custom Feed
A strong milk fever prevention program starts before calving, with dry-cow feed management that supports body condition, mineral balance, feed intake, and a smoother transition into lactation.
Custom animal nutrition formulas can help optimize the cation-anion ratio to reduce the risk of milk fever while maximizing your herd’s productivity and health. Using the correct anionic minerals, the right forages and concentrates, enough magnesium, and precise balancing depend on following a livestock nutritionist’s recommendations.
Star Blends can work directly with your nutritionist to build feed around your herd’s specific mineral and nutritional needs. Milk fever is among the most preventable cow disorders when you have the right ration in the bunk. Contact Star Blends today to support a transition program that keeps cows eating, freshening well, and producing.
