Ruminants

All you need to know about milk fever in cows

Calcium deficiency during calving, also known as hypocalcemia in cattle, paresis puerperalis, or parturient apoplexy, leads to “milk fever” in high-yielding cattle. This condition is one of the most serious metabolic diseases affecting bovines. Hypocalcemia in cattle often leads to other metabolic issues, including retained placenta, ketosis, mastitis, uterine infections, and fatty liver syndrome.

This article delves into the risks, causes, symptoms, and treatments associated with milk fever in cows.

Risks associated with milk fever in cows

Milk fever, or hypocalcemia, in cows, is a critical condition that arises from a sudden drop in blood calcium levels, typically around the calving period. This metabolic disorder disrupts essential physiological processes, as calcium is vital for muscle contraction, nerve function, and overall metabolic stability. The condition poses significant risks to the health and productivity of affected cows, making it a concern for dairy farmers globally. Let’s take a detailed look into some of the risks associated with milk fever in cows:

Magnesium plays a crucial role in synthesising and releasing parathyroid hormone (PTH), which is essential for maintaining calcium balance in the blood. PTH mobilises calcium from bones, enhances calcium absorption in the intestines, and reduces excretion through urine, ensuring optimal levels are maintained for vital functions such as muscle contraction and nerve signalling.

When magnesium levels are insufficient, the production and function of PTH are impaired, leading to reduced calcium regulation.

80-90% of milk fever cases in cattle are linked to inadequate magnesium intake.

For this reason, experts recommend that pre-calving diets contain at least 0.4% magnesium in the dry matter. Cows with milk fever produce less milk for 4 to 6 weeks after calving.

Subclinical milk fever can weaken the immune system, making cows more vulnerable to other diseases that impact milk production.

Here are some other risks associated with milk fever in cows:

Cows with previous incidences of hypocalcemia
Diets with high in potassium and calcium
High calcium intake before calving
Low magnesium intake during the dry period
Low intake of roughage
Cows aged 5 years or greater
Jersey breed has fewer Vitamin D receptors than Holstein cattle
Overweight cows

Causes for milk fever in cows

Milk fever, also known as hypocalcemia in dairy cattle, occurs when blood calcium levels drop below the necessary threshold to support essential bodily functions.

The clinical signs of milk fever can be identified in 3 stages:

Stage 1: The cow might refuse to eat. It may show signs of aggression or fear. The cow can also have ataxia, which means a lack of coordination. They may experience tremors and bloat.

Stage 2: The cow will likely be in sternal recumbency, with a full udder and a rectum distended with feces. The muzzle may appear dry.

Stage 3: The cow may lie on its side. It may show signs of bloat, lower body temperature, and slower breathing and heart rates.

Here are some other factors that cause hypocalcemia in dairy cattle:

Poor quality dry cow feed: This can prevent the cow’s body from generating enough calcium
Dry cow feed: Feed that’s high in calcium (over 100 to 125 g/kg) can inactivate the parathyroid gland
High milk production: Each liter of milk needs a specific amount of calcium. More milk means more calcium loss.

After giving birth, a cow’s calcium requirements nearly double due to the intense demand for calcium in milk production. Specifically, she needs approximately 2.3 grams of calcium per liter to produce colostrum, the nutrient-rich first milk essential for the newborn’s immune system and development.

In older cows, the mobilization mechanism often does not start quickly enough. The supply from the bones and feed is insufficient, and the body extracts the missing calcium from the muscles. This eventually leads to symptoms of paralysis and overstimulation of the nervous system.

Symptoms of milk fever in cows

Mostly 90% of milk fever cases in cows occur within 24 to 48 hours before or after calving.

Understanding the symptoms of milk fever in cows requires deeper knowledge of the different stages involved.

Stage 1

Here are some of the subtle symptoms of milk fever in cows during the initial stage which most of the time go unnoticed:

Muscle tremors
Restlessness
Stiff gait
Slightly elevated temperature

Stage 2

At this stage, hypocalcemia symptoms in cattle usually last for 1 to 12 hours. The cow often shows a unique neck position. The animal will lie down with its head tucked into its flank, creating an S-shaped neck. Early symptoms of paralysis appear:

Fast, flat pulse
Cold body surface
Dilated pupils
Flatulence

Stage 3

During the final stage of hypocalcemia in cattle, the cows are completely paralyzed and lie flat on their side. They are often bloated, lose consciousness, and fall into a coma. The temperature continues to drop and the heart rate shoots up to 120 bpm. Without an effective treatment, these cows will die in a few hours.

The third phase often leads to death wherein the mortality rate averages from 2% to 5%.

Treatment for hypocalcemia in cattle

Hypocalcemia in cattle can be treated in various ways if addressed promptly:

Intravenous Calcium Infusion: The most effective method involves administering calcium gluconate directly into the jugular vein. You should complete this slowly over 10–20 minutes to avoid heart complications, such as arrhythmias. It typically provides an immediate response, with 75% of treated cows able to stand within two hours. The standard dose is 500 mL of a 23% calcium borogluconate solution, delivering 10.7 g of calcium.

Oral Calcium Supplements: After treatment, people use oral calcium boluses or gels. These usually contain 50 to 70 grams of calcium per dose to prevent relapse. The medical team gives them 12 to 24 hours after the first IV treatment. This is only if the cow is alert and can swallow.

Subcutaneous Calcium Injection: For mild cases or relapse prevention, subcutaneous administration of calcium borogluconate is a secondary option. Medical professionals inject doses of 125 mL at multiple sites, ensuring they use aseptic techniques to avoid infections.

Supportive Therapies: Magnesium and phosphorus supplementation may support calcium metabolism. However, these should be used cautiously, as unnecessary electrolytes could complicate recovery.

Acidogenic Diets: Preventively, an acidogenic diet is fed for 3 weeks before calving to help mobilize calcium reserves effectively. This involves adjusting the dietary cation-anion difference (DCAD) to maintain calcium homeostasis.

Prevention of milk fever in cows

Various nutritional strategies are available for effectively preventing milk fever in cows:

Limiting calcium intake: Less than 100g per cow per day for two to three weeks before calving
Reducing potassium intake: Keep potassium levels as low as possible, ideally less than 1.5%
Feeding anionic salts: Anionic salts, such as ammonium sulfate, ammonium chloride, and magnesium sulfate, can prevent milk fever
Supplementing magnesium: Supplement magnesium at a rate of 15 to 20g per day
Supplementing calcium after calving: Supplement calcium to susceptible animals after calving
Administering Vitamin D: Administer vitamin D, vitamin D metabolites, and analogues prepartum

To summarize, milk fever in cows is a serious yet manageable condition that requires timely intervention and proactive measures. By knowing the causes, symptoms, and treatments, animal nutritionists can prevent milk fever. This keeps their cows healthy and productive.

Checking calcium levels regularly (via blood tests, calcium serum tests, urine tests, or clinical observation) can reduce the risk of milk fever. Changing diets before calving is also important. Additionally, maintaining a good mineral balance is beneficial.

By diagnosing problems early and using the right prevention methods, farmers can protect their herds. This ensures a steady milk supply and supports overall farm success.

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