Milk Fever in Cows: Causes, Symptoms & How to Prevent It

Milk fever in cows, medically called hypocalcemia, is a sudden drop in blood calcium that typically occurs within 24-72 hours of calving, when a cow’s calcium demand for colostrum and milk production spikes faster than her body can supply it. Early signs include muscle weakness and unsteady movement; if untreated, it progresses to an inability to stand. It’s most common in cows in their third lactation or later. Treatment involves intravenous calcium under veterinary supervision, but prevention through correct dry-period mineral management is far more effective — and far less risky — than treating an active case.

Introduction

A cow calves overnight, and by morning she’s down in the stall, unable to rise, ears cold to the touch. For dairy farmers, this is one of the most alarming — and most common — emergencies around calving season.

The good news is that milk fever is one of the most predictable and preventable metabolic disorders in dairy cattle. This guide covers what actually causes it, the signs to watch for before it becomes an emergency, and the prevention strategies that genuinely reduce risk.

What is Milk Fever in Cows?

Milk fever, or hypocalcemia, is a metabolic disorder caused by a sudden drop in blood calcium around the time of calving. Despite the name, it has nothing to do with body temperature — there is no actual fever involved.

It strikes during the transition period — roughly three weeks before to three weeks after calving — when a cow’s calcium demand suddenly outpaces her ability to supply it. After calving, a cow’s calcium requirement can increase by roughly 400% compared to the dry period (University of Wisconsin–Madison), because colostrum and milk are extremely calcium-rich. To meet that demand, she must rapidly pull calcium from her diet and, when that’s not enough, from her own bone reserves. When she can’t mobilize enough fast enough, blood calcium falls and clinical signs appear.

There are two distinct forms:

• Clinical milk fever — visible, obvious symptoms; a veterinary emergency
• Subclinical hypocalcemia — no obvious symptoms, but still damages health and productivity, and is far more common than most farmers realize

Milk Fever in Cows: Signs and Symptoms

Recognizing the early signs before a cow goes down completely is the single most useful skill a farmer or herd manager can have.

Early signs:

• Muscle tremors, especially around the head and limbs
• Mild agitation or excitement
• Reduced appetite and rumen activity
• Unsteady gait or slight staggering

Progressing signs:

• Inability to stand normally; the cow adopts a “sitting” sternal position
• A characteristic kink in the neck
• Cold ears, legs, and muzzle
• Dry muzzle and staring eyes
• Body temperature falling below normal

Advanced signs (emergency):

• Complete inability to rise; lying flat on her side
• Bloat, since the cow cannot sit upright to release rumen gas
• Weak, rapid heartbeat
• Progression to circulatory collapse and coma if untreated

Roughly 80% of clinical milk fever cases occur within the first 24 hours after calving, which is exactly why close monitoring during this narrow window matters so much.

Milk Fever in Cows Before Calving: Can It Happen Pre-Calving?

While milk fever is most strongly associated with the days immediately after calving, the underlying calcium imbalance actually begins building in the final weeks of pregnancy. This is why the “transition period” — three weeks before calving through three weeks after — is the window veterinarians focus on, not just the calving day itself. Poor mineral management in this pre-calving window (particularly excess dietary calcium or an imbalanced potassium intake in forage) is one of the biggest predictors of a clinical case after calving.

Causes of Milk Fever in Cows

• The calving calcium surge — colostrum production drains blood calcium almost instantly, faster than most cows can naturally compensate for.
• Age and lactation number — older cows, typically in their third lactation or later, have a significantly weaker ability to mobilize calcium from bone reserves, making them far more susceptible than first or second calvers.
• Excess dietary calcium before calving — counterintuitively, feeding too much calcium in the close-up dry period can suppress the hormonal mechanisms that would otherwise mobilize calcium quickly when it’s actually needed.
• High dietary potassium in forage — forages with high potassium content interfere with the cow’s acid-base balance in a way that increases milk fever risk; this is a key reason forage testing matters.
• Higher milk yield — as dairy cows are bred and managed for higher production, calcium demand at the start of lactation rises faster than the body’s natural mobilization response.
• Reduced intestinal calcium absorption — absorption efficiency can be temporarily impaired right around calving, compounding the sudden demand.

Milk Fever in Cows: Treatment

Active clinical cases require prompt veterinary treatment. The standard approach includes:

1. Intravenous calcium (commonly calcium gluconate), administered slowly under veterinary supervision — rapid IV calcium can dangerously affect heart rhythm, so this should never be attempted without guidance.
2. Subcutaneous or oral calcium follow-up, often given several hours after the initial treatment to help sustain blood calcium as the cow’s own regulatory systems recover.
3. Monitoring for relapse — some cows respond initially but relapse within 24-48 hours and need a second round of treatment.

It’s worth being clear: different forms of calcium treatment (IV, subcutaneous, oral) are not interchangeable, and using the wrong form or dose without veterinary guidance can do more harm than good. Subclinical cases, which have no obvious symptoms, are generally managed through nutritional correction rather than emergency IV treatment — unnecessary IV calcium in a subclinical cow can actually suppress her own calcium-regulating response.

How to Prevent Milk Fever in Cows

Because milk fever can progress from first symptoms to a life-threatening emergency within hours, prevention is far more valuable — and far less risky — than treatment. Proven strategies include:

• Test forage mineral content before feeding it to dry cows, and select forages with low potassium content where possible.
• Manage the DCAD (Dietary Cation-Anion Difference) of the pre-calving ration — many farms use controlled anionic salt diets in the close-up dry period specifically to support the cow’s calcium-mobilizing mechanisms before calving.
• Monitor urine pH in cows on an anionic diet as a practical check that the mineral program is actually working — target urine pH is typically in the 6.0-6.5 range.
• Avoid excess calcium in the close-up dry period — it seems counterintuitive, but restricting calcium slightly before calving trains the body’s hormonal response to mobilize it efficiently when demand spikes.
• Ensure constant access to clean water for dry cows — adequate water intake is directly tied to how much dry matter (and therefore minerals) a cow actually consumes.
• Give extra attention to cows in their third lactation or later, since age is one of the strongest risk predictors.

Clinical vs Subclinical Milk Fever

Consequences of Untreated or Repeated Milk Fever

Even when a cow survives an episode, milk fever — clinical or subclinical — is linked to a higher risk of related problems, including:

• Retained placenta
• Uterine infections and endometritis
• Increased susceptibility to mastitis
• Displaced abomasum
• Reduced milk yield in the lactation that follows
• Delayed return to breeding

This is why even a single clinical episode should prompt a review of the herd’s entire transition-period nutrition program, not just treatment of the individual cow.

Why This Matters for Indian Dairy Herds

India’s dairy sector is built on a massive livestock base — over 193 million cattle and 109 million buffaloes, the largest such population in the world. With calving happening across millions of animals every year, even a moderate herd-level incidence of subclinical hypocalcemia represents a significant, largely invisible drag on national milk output. For individual farmers, this translates directly to lost income — the difference between a cow that transitions smoothly into her next lactation and one that starts it compromised.

FAQs

Q1. What are the signs of milk fever in cows?

Early signs include muscle tremors, mild agitation, and reduced appetite. As it progresses, the cow may be unable to stand, develop a kinked neck posture, and have cold ears and legs. In advanced cases, she may be unable to rise at all and develop bloat, requiring emergency veterinary treatment.

Q2. What causes milk fever in cows?

The main cause is a sudden spike in calcium demand after calving for colostrum and milk production, combined with the body’s calcium-mobilizing mechanisms not activating fast enough. Risk increases with age and lactation number, excess dietary calcium before calving, and high-potassium forage.

Q3. Can milk fever happen before calving?

The clinical episode is most common in the first 24-72 hours after calving, but the underlying calcium imbalance builds during the final weeks of pregnancy. This is why prevention strategies focus on the 3-week pre-calving window, not just the day of calving itself.

Q4. How is milk fever in cows treated?

Active clinical cases are treated with intravenous calcium under veterinary supervision, often followed by subcutaneous or oral calcium to sustain levels. Different calcium formulations are not interchangeable, and treatment should always be guided by a veterinarian rather than administered blindly.

Q5. How can milk fever in cows be prevented?

The most effective prevention strategies involve managing the dry-period ration — testing forage for potassium content, using controlled anionic salt (DCAD) diets before calving, and avoiding excess dietary calcium in the close-up period, alongside ensuring constant clean water access.

Q6. Which cows are most at risk of milk fever?

Cows in their third lactation or later face significantly higher risk, since older cows have a reduced ability to mobilize calcium from bone reserves compared to first or second calvers. High-yielding cows are also more susceptible due to greater calcium demand at the start of lactation.

Sources

• University of Wisconsin–Madison — Dairy Cattle Transition Period Nutrition
• University of Minnesota Extension — Prevention and Treatment of Hypocalcemia
• Phibro Animal Health — Milk Fever: Causes, Symptoms and Prevention
• Lowline Cattle Association — Milk Fever (Hypocalcaemia) in Cows, Technical Note

Related Reading

• Mastitis in Cows: Causes, Symptoms & Treatment
• GMP Certified Veterinary Manufacturer in India: Why WHO-GMP Matters

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Disclaimer: This article is for general awareness only and is not a substitute for veterinary diagnosis or treatment. Milk fever, especially in its clinical form, can be a medical emergency — always contact a veterinarian promptly if a cow shows signs of hypocalcemia.