29 March 2021

Milk fever in cows: everything you need to know, including 2021 update

1 What is milk fever in cows?

11 minute read

Milk fever is a complex metabolic disease in cows, that usually occurs around calving and most commonly in high-productive cows from three years and older. It is one of the most common mineral-related metabolic diseases affecting dairy cows and is also known as calcium deficiency, hypocalcemia, and parturient paresis. In this article, we will tell you everything you need to know about milk fever: how to recognize it, prevent it, treat it,… And we will update you on the most recent scientific research on this topic.

Lying behavior is a sign of milk fever in cows"Cows with clinical hypocalcemia spend more time lying down."

2 Symptoms of milk fever in cows

A cow with milk fever usually shows very general symptoms of illness which appear when the blood calcium levels are low: she has a lack of appetite, lower body temperature, looks groggy, and has difficulties producing manure and urine (also known as subclinical milk fever). If not treated the cow will be unable to stand and will lay down in a typical position (known as clinical milk fever): on her chest with her head on her side. In other cases, the cow will lay on her side, or sit down the way a dog does.

Furthermore, hypocalcemia is associated with diabetic-like conditions like increased blood glucose and the inability to release insulin at calving.

3 What causes milk fever in cattle?

So now that we know the symptoms of milk fever it is time to look at the causes. Knowing the causes will help us in better understanding the treatment and the prevention.

3.1 When does milk fever occur?

As we already mentioned, milk fever in cattle is a metabolic disease that occurs around calving. More precisely, three to four days before calving the levels of calcium and inorganic phosphorus in the blood serum drop. The drop in calcium is a consequence of the start of milk production, whereas the drop in phosphorus is a direct result of calving itself. Cows with milk fever, however, experience a greater drop in these minerals than cows without the disease. Cows with serum calcium lower than  7,5 mg/dL are considered hypocalcemic.

Plasma calcium concentrations around time of parturition in milk fever.Plasma concentrations of total calcium before and after calving in mature Jersey cows with (MF) or without (NMF) clinical milk fever (Kimura et al., 2006).

3.1.1 Hormonal changes: Start of lactation

At the moment that the cow is adapting hormone-wise to lactation, there is a big difference between the supply of calcium and the demand for the fetus and colostrum/milk. In a single milking, a cow can lose about 23 g of calcium, which is 9 to 10 times more than the calcium supply. This gap must be filled by either increasing the absorption from the gut or bones or decreasing the outflow of calcium other than to milk.

It is important to note that milk fever is a production disease, meaning that as milk production increases the prevalence and severity of milk fever generally increases as well.

3.1.2 Hormonal changes: other findings

Other hormonal changes around calving have also shown to be an antecedent of milk fever. Increased estrogen and glucocorticoids may reduce serum calcium. Furthermore, increased estrogen is known to reduce appetite. Also, stress from calving may prompt the release of a number of hormones that reduce blood calcium.

3.1.3 Dry cow feed: calcium to phosphorus ration

We find another reason for the occurrence of milk fever in the dry cow feed. Dry cow feed high in calcium (over 100 to 125 g/kg) has proven to inactivate the parathyroid gland. However, around calving, the need for calcium is extremely high. In consequence, an inactive gland suffers to adequately supply calcium to the blood, leaving the cow with a calcium deficiency.

As for phosphorus, it is shown that rations high in phosphorus interfere with the metabolism of vitamin D, especially with the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol.

3.1.4 Dry cow feed: other findings

Another feed-related cause of milk fever can be a reduced intake of feed around parturition, again with older cows showing a greater reduction of intake in the last four days before calving.

3.1.5 Breed

Although reasons are unclear it is known that certain breeds are more susceptible to milk fever than others, in particular Channel Island, Swedish red and White, and Jersey cattle.

3.1.6 Age

How much the levels of calcium and inorganic phosphorus in the blood serum drop, is highly dependable on the cow itself, with older cows showing a bigger drop since they absorb less dietary calcium and may have less exchangeable bone calcium. Research by Jönsen showed that the percentage of cows with milk fever is highest in the group that had 9 calvings. Or in short: as dairy cows become older, the prevalence of milk fever increases.

4 Treatment for milk fever

A cow getting an infusion against hypocalcemiaIf prevention failed, treatment is necessary. Without treatment 60 to 70% of the affected cows will die. In the 1800’s milk fever in cows was treated using hot packs, blankets, cayenne pepper, and alcohol. Needless to say, these treatments were rather ineffective. It was only in 1925 that the current treatment was adapted. Once a cow is laying down a veterinarian gives a calcium infusion to the animal. This keeps the cow alive until the cow is adapted to the higher demand for calcium.

4.1 How long does milk fever last?

In most cases, the infusion makes for a quick recovery of the cow. However, about 25% of the cows need additional treatment. And although treatment is usually very fast, many cows tend to be recidivists and the productive life of dairy cows can be reduced by more than three years.

5 How to prevent milk fever in cows?

The best treatment for milk fever is prevention.  There are numerous ways to prevent the calcium level in the blood serum from getting too low:

5.1 Feed

  • Correct animal feed prevents milk fever in cattleLow calcium: Give rations low in calcium and (relatively) higher in phosphorus during the dry period of the cow. In this way, the calcium metabolism will be activated. At calving, the parathyroid gland will be better prepared to mobilize calcium from the bones, and calcium from ration and supplements will be better absorbed. This strategy is still effective on many farms. A 2002 study by Hansen and colleagues found this strategy to be highly efficient if the calcium intake is less than 20 g per day. However, formulating rations this low in calcium proves to be difficult.
  • DCAD (Dietary Cation-Anion Difference): In regions where the low calcium-strategy isn’t effective, the DCAD-strategy might be applied. By giving the dry cow anionic salts like potassium chloride at least 10 days before calving, the calcium absorption during the dry period will be lower as well. Although effective, this strategy also comes with a lot of warning: anionic salts need to be rationed daily, aren’t very tasty, need regular pH-testing, and might even increase milk fever levels when not done correctly.
  • Dietary magnesium control: Dry cows should receive sufficient magnesium since numerous studies show that hypomagnesemia is highly related to milk fever.
  • Feeding grain up to 1% of body weight during the dry period has shown to decrease the prevalence of milk fever.

5.2 Supplementation

  • Supplementation of vitamin D 3 to 8 days before calving. This has to go together with sufficient levels of calcium and phosphorus in ration and/or supplements. Vitamin D is important for the intestinal absorption and bone mobilization of calcium, however, caution is needed as over-supplementation or supplementation 1 day before calving may increase the chances of milk fever or other toxicological effects.
  • Supplementation of a rapid-action calcium supplement in the 24 hours before and after calving. Many commercial products are available in different forms: liquid, gel, paste, and bolus. They also serve as a therapy for the prevention of milk fever relapses.Bolusing can prevent milk fever in cows

5.3 Other

  • Body condition score: Energy intake of cows in mid and late lactation should be monitored as it is important to prevent the dry cow from getting too fat.
  • Provide comfort and a clean box to reduce stress.
  • Implement specific control programs when the prevalence of milk fever in cows at high risk increases to above 10%.
  • Shortening the dry period may reduce the incidence of milk fever in cattle, but would also reduce milk production in the following lactation.

6 Economic consequences

An estimated 3 to 8 % of cows are affected by clinical milk fever. The production loss for cows suffering from milk fever is huge and so is, of course, the economic impact. The average cost, including medicines, veterinary services, and estimated production loss, amount up to 334 USD per case. However, it is important to note that subclinical milk fever also comes with a cost of up to 125 USD. It is even believed that the tDairy farms suffer economic losses from milk fever in cowsotal cost because of subclinical milk fever is 4 times higher than the cost of clinical milk fever.

As mentioned before, the productive life of a cow suffering from milk fever may lower dramatically. When the milk yield doesn’t recover to economically feasible amounts the cow also needs to be culled.

In addition, they also are more susceptible to secondary diseases like ketosis and mastitis. Research by Curtis showed that cows having suffered from milk fever have ketosis and mastitis 8 times more often.

7 Recent studies

Hendriks and colleagues (2020) studied the “associations among blood calcium (Ca) status at calving and lying behavior and activity measures during the transition period in grazing dairy cows.” Cows with clinical hypocalcemia (but without milk fever) were found to be less active on the day of calving and spend more time lying down (also on the night before calving) than subclinical hypocalcemic and normocalcemic cows. These differences however disappeared two days after calving.

A study on 30 local breed cows in Iraq (Hassan et.al., 2020) showed known signs of milk fever and confirmed the idea that older cows are more susceptible to milk fever.

Goff and colleagues (2020) studied the effect of hypocalcemia on rumination activity. They confirmed their hypothesis that milk fever reduces rumination activity, even to the point that cows given an intravenous calcium treatment almost show no activity at all.

When studying 32 Holstein X Gir dairy cows, Rodrigues and colleagues found an impact of subclinical hypocalcemia on energy levels, somatic cell count, and milk components during early lactation. More specifically, these cows had less serum insulin, a greater somatic cell count, and lower concentrations of milk fat, protein, and lactose.

For a recent meta-analysis on milk fever in cattle, we recommend reading “Symposium review: Transition cow calcium homeostasis—Health effects of hypocalcemia and strategies for prevention” (Wilkens et.al., 2020).

8 Our solution

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Calcitop calcium bolus to prevent milk fever in cows

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9 Bibliography "Milk fever in cattle: everything you need to know - 2021 update"

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Wilkens, M. R., Nelson, C. D., Hernandez, L. L., & McArt, J. A. A. (2020). Symposium review: Transition cow calcium homeostasis—Health effects of hypocalcemia and strategies for prevention. Journal of Dairy Science, 103(3), 2909–2927.

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