The evolution of milk fever mitigation

Rod Martin knows how efforts to mitigate milk fever have evolved over the years. He shared his decades of experiences in a recent Dairy Herd Management article and offered advice for the future.

Rod, a Protekta dairy nutritionist with more than 35 years of experience and unparalleled insights into managing hypocalcemia, says that back in the ‘80s the focus was on minimizing dietary calcium levels to address milk fever. But the daily calcium limits suggested by the research were not practical in the field.

In the early ‘90s, the correlation between high potassium diets and increased milk fever rates was discovered. Consequently, producers and nutritionists quickly adapted low-potassium diets utilizing forages such as grass hay and corn silage. As hypocalcemia research continued to advance through the next two decades, negative dietary cation-anion difference (DCAD) diets evolved. They not only incorporated potassium but also added sodium, chloride and sulfur to the dietary analysis.

Fast forward to the 2020s. Milk fever and subclinical hypocalcemia mitigation is focused on dietary phosphorus and practical strategies to minimize daily phosphorus intake.

All this progress over the years has led to a low incidence of clinical milk fever, but subclinical hypocalcemia is still unacceptably high. To continue on the right path to controlling this metabolic disorder, more attention needs to be paid to excess phosphorus, Rod says.

Read the full story about the evolution of milk fever mitigation in Dairy Herd Management.

After that, read our summary of the science behind the role of dietary phosphorus in improving blood calcium and preventing hypocalcemia. It details a recent presentation by Pat Hoffman, Professor Emeritus at the University of Wisconsin.

Rod Martin’s article first appeared in Dairy Herd Management. A presentation on the science behind the role of dietary phosphorus in improving blood calcium and preventing hypocalcemia was given by Pat Hoffman, Professor Emeritus, University of Wisconsin.

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The Role of Dietary Phosphorus in Hypocalcemia

This summary is based on the Hoard’s Dairyman webinar by Pat Hoffman, Professor Emeritus, University of Wisconsin

Hypocalcemia or “low blood calcium” is still a common health issue in dairy cows at the initiation of lactation. The condition ranges from the clinical manifestation known as “milk fever” to a subclinical occurrence that is discernable by low blood calcium but shows no outward evidence of the disease. A cow with clinical milk fever is recumbent and unable to walk. Less dramatic but equally concerning is subclinical hypocalcemia (blood calcium below 8.5 mg/dl). Cows experiencing subclinical hypocalcemia may have reduced dry matter intake, lowered immune response, decreased milk production, and poor reproductive performance. In addition, they are at a higher risk of developing other health issues, such as mastitis, metritis, displaced abomasum, and retained placenta, which collectively leads to a higher cull rate.

Negative effects of hypocalcemia

Over the years, different dietary management strategies have been studied to reduce the risk of milk fever and improve blood calcium levels. “A common dietary management practice has involved manipulating calcium homeostasis to improve blood calcium,” said Hoffman. “A more recent approach, which is a paradigm shift in how we discuss mitigating milk fever, is directed at manipulating phosphorus homeostasis to achieve the same blood calcium improvement.”

The biology of this improvement in blood calcium through manipulating phosphorus homeostasis hasn’t been well studied until recently. In 2020, Walter Grunberg’s research group fed a pre-fresh diet adequate in dietary phosphorus – 0.30% DM – and compared it against a diet that had restricted dietary phosphorus – 0.16% DM (Effects of restricted dietary phosphorus supply during the dry period on productivity and metabolism in dairy cows). This low level of dietary phosphorus of 0.16% DM was accomplished by slightly restricting feed intake and sourcing feedstuffs extremely low in dietary phosphorus. The cows fed a diet restricted in phosphorus had higher blood calcium at calving and increased markers of bone mobilization. This study supported previous work performed by Grunberg’s group that initially showed manipulating phosphorus homeostasis improved blood calcium and suggested the blood calcium benefit was working through increasing bone mobilization.

According to Hoffman, the mechanism of phosphorus homeostasis has only recently been unraveled. Phosphorus homeostasis is primarily regulated by the bone hormone Fibroblast Growth Factor-23 (FGF-23). This hormone and mechanism appear to be independent of the PTH mechanism that regulates calcium homeostasis. When blood phosphorus is reduced, levels of FGF-23 decrease, which in turn increases bone mobilization, liberating both calcium and phosphorus to the blood. Additionally, depressed FGF-23 can increase vitamin D activation and subsequent absorption in the intestinal tract.

X-Zelit®, a dietary phosphorus binder, is a novel approach to induce a mild hypophosphatemia through restricting dietary phosphorus to reduce milk fever and subclinical hypocalcemia. It capitalizes on manipulating phosphorus homeostasis, rather than the calcium homeostasis.  X-Zelit is a research-proven strategy that is commercially available and recommended to be fed for 14-21 days pre-fresh to prevent milk fever and subclinical hypocalcemia.

After Hoffman discussed the biology of X-Zelit, he discussed practical implications at the farm level. The X-Zelit approach offers advantages beyond the consistent improvement in blood calcium levels and reduction in milk fever and subclinical hypocalcemia. Other advantages of X-Zelit diets include eliminating the need to check urine pH, removing the hassles of procuring low potassium forages and formulating for low potassium diets. This offers farms the flexibility to feed alternative home-grown forages, ones that are typically higher in potassium as well as protein (rye, sorghum, haylage). Hoffman made sure to point out that X-Zelit is only a pre-fresh product; this strategy does not fit a one-group dry cow strategy and should only be fed in the close-up diet for 14-21 days.

In summary, Hoffman described how current-day research has brought a novel approach to improving blood calcium and preventing hypocalcemia through the incorporation of  X-Zelit usage pre-fresh. This unique approach involves inducing a mild hypophosphatemia to trigger bone mobilization and significantly improve blood calcium concentrations in transition cows. It helps take the negativity out of your pre-fresh program.

dairy cows eating at bunk in a freestall

Dairy Global: A cost-effective approach to stamping out milk fever

Milk fever is still a common dairy cow health issue around the world, but the use of new preventative products, especially synthetic zeolite, is now turning the tide thanks to US research.

Zeolite is a specific family of ‘hydrated aluminosilicate’ minerals that can be produced in synthetic form and is commercially available to feed to pre-fresh dairy cows.

“We are still seeing milk fever on dairy farms in Wisconsin and beyond,” says Patrick Hoffman, Professor Emeritus at the University of Wisconsin-Madison. “However, at this point in time, we now have an alternative way of preventing milk fever and subclinical hypocalcemia by feeding synthetic zeolite 2-3 weeks before calving. As its use spreads, we should see a reduced incidence of hypocalcemia. Zeolite is a very interesting entry into the milk fever prevention market.”

Hoffman notes that in the US and Canada in particular, knowledge about this product is already at a high level. “Most dairy nutrition consultants are aware of feeding zeolite to pre-fresh cows and are working with it to some degree,” he says. “Adoption has happened relatively quickly. Feeding zeolite to prevent milk fever started with a group of researchers in Europe experimenting with natural and synthetic zeolite about 20 years ago. About a decade ago zeolite was introduced in Canada and then into the US.”

Knowledge building

Researchers have known for a long time that feeding excessive levels of phosphorus (P) pre-calving was causing an increase in milk fever (calcium, CA, deficiency) at calving. However, for many years the reasons for this observation were unclear. Scientists now also understand that a peptide hormone active in bone tissue (called fibroblast growth factor 23) can regulate bone resorption of Ca and P (and urinary retention of P).

“About 20 years ago in Europe, they observed that feeding synthetic zeolite before calving elevated levels of blood Ca at calving,” says Hoffman. “They thought zeolite was directly working to cause the release of Ca from the bone (mobilisation) and improved intestinal absorption of Ca before calving, but that wasn’t exactly correct.”

That early research (and research since) has also shown that feeding zeolite before calving consistently reduces blood P levels, which induces bone mobilisation of Ca and P.

However, recently a University of Wisconsin-Madison team led by Dr Laura Hernandez figured out how zeolite was affecting the binding of P and not Ca per se. In their study, feeding zeolite to pre-fresh cows decreased blood and salivary P levels and increased faecal excretion of P. The cows responded to the lower blood P levels by mobilising bone.

These insights into P metabolism, says Hoffman, have made it easier to figure out how to use zeolite and balance the diet of a pre-fresh cow.

Other ways of mitigating milk fever

The team at the University of Wisconsin-Madison continues to study zeolite, but Hoffman says Hernandez and her colleagues have also been studying a compound called 5-HTP, a form of the amino acid tryptophan.

“They’ve discovered that the mammary gland itself can send signals to the rest of the body that it is in need of calcium,” Hoffman explains. “A supplement form of 5-HTP is now being commercialised and it’s very exciting. The team speculates that it may work in concert with zeolite, but that needs to be studied. Whatever is simplest and most effective at the farm level will be implemented on farms.”

Researchers are also testing the supplementation of a plant called Solanum glaucophyllum, which contains the metabolically-active form of Vitamin D, D3. Giving small amounts of this plant in a bolus has been shown to increase blood Ca levels, but Hoffman says that form of application may be labour-intensive and so commercialisation of another format may be a better way forward. Still, other researchers are working on other products that increase Ca absorption from the intestine, such as difructose anhydride.

Zeolite use

Preventing milk fever around the world through giving synthetic zeolite will require education, says Hoffman. “We need to build an infrastructure of nutritionists, veterinarians and farmers who understand the mechanism is new and different.”

He explains that when zeolite is fed, blood P values are going to decrease at calving, which is what needs to happen, and after calving blood P levels will rise quickly to 4 to 6 mg per decilitre (within 24-48 hours).

“Almost all dairy cows experience a transient phase in which blood P decreases at calving then increases quickly after calving,” says Hoffman. “It’s nothing new, but feeding zeolite induces this earlier. So it’s a paradigm shift in thinking about how blood P levels influence milk fever.”

Zeolite should also be fed at the right amount and for the right length of time. Because zeolite binds P, feeding it for too long might cause a P depletion. “Zeolite is fast-acting and is needed only for about 2 weeks, at least a week before calving,” Hoffman explains, “but since we don’t know exactly when calving will occur, we can start 2-3 weeks before.” Zeolite must also be mixed properly into the diet.

Another benefit to feeding zeolite before calving is that the cost is reasonably comparable to other milk fever prevention programs.

Hoffman explains that by feeding zeolite, farmers have to worry less about excess potassium going into the cow (and don’t have to monitor urine pH). This means farmers can feed their own higher-quality forages (alfalfa silage or grass silage) containing more protein and potassium. The need for purchasing low-potassium forages is avoided, protein supplementation costs may go down and that helps pay for the zeolite.

Hoffman adds that many dairy farmers who use zeolite also report that they don’t use as many calcium boluses, which also saves costs.

However, feeding synthetic zeolite is difficult to use in a 1-group dry cow situation, if cows are in the pre-fresh pen for long periods of time (greater than 28 days) and in overcrowded pre-fresh pens.

Worldwide use

Used correctly, zeolite represents a significant advancement in the prevention of milk fever.

Hoffman notes that Ca deficiencies at calving have many negative effects on cow performance, in addition to costing money and requiring more labour. While the second phase is easy to recognise due to clear symptoms, the consequences of early calcium deficiency are not easily detectable and can often be underestimated. In addition, cows that suffer from Ca deficiency have been shown to be more susceptible to other diseases.


This article was written by Treena Hein and first appeared in Dairy Global on Sept. 7, 2023.

sunny morning dairy cows eating at bunk

Low Colostrum Production: Lots of Questions…Not as Many Answers

Questions concerning low colostrum production are common throughout the year but are much more prevalent during the Fall. This phenomenon is not new, as our industry has dealt with this issue for the last 20+ years. We continue to hear questions from dairy producers, “We never saw these colostrum issues years ago,” “Why does it always happen during the Fall season?” “Is there something missing in the pre-fresh diet?” To answer these questions and provide effective on-farm solutions, we first need to start with what we do know. 

We do know that photoperiod has a dramatic effect on colostrum production. Research has shown a highly significant effect on colostrum production as daylight decreases, with the lowest colostrum yield occurring in December, which has the shortest days of the year. On average, mature cows (2+ lactation) that calve in June produce 3X more colostrum than mature cows that calve in December. In fact, field studies report that up to 35% of mature cows give ZERO colostrum at calving during the month of December. Eventually, these cows will come into milk and early lactation milk production is not affected. 

Since we cannot change seasonality and the associated photoperiod effect, what are the on-farm checkpoints that we need to closely evaluate when colostrum production is challenged: 

  1. Pre-fresh Dry Matter Intake (DMI): Maintaining a high and consistent DMI is critical for fresh cow success and colostrum production. Factors that can negatively impact DMI include overcrowding, bunk management, TMR particle and moisture consistency, forage fermentation issues, molds and mycotoxins, too little time in the pre-fresh group, excess cow moves, etc. Work closely with your nutritionist and management team to identify and minimize these potential bottlenecks that may limit colostrum production.
  2. Pre-fresh Fiber Sources & Length: Dry cow and pre-fresh diets containing high levels of straw and/or grass hay have become common in the last 20 years due to higher and more consistent intakes that increase gut fill which results in better fresh cow health. With higher levels of straw/grass hay, comes the challenge of achieving a consistent particle size and optimal moisture level to minimize sorting. In addition, some straw/grass hay may contain potential antagonists that could interfere with the hormonal changes required for the initiation of colostrum synthesis and parturition.
  3. Pre-fresh Dietary & Management Compliance: Review the key nutrients essential for colostrum production with your nutrition team and management staff. Ensuring that a well-balanced diet is formulated and correctly implemented provides another opportunity for colostrum success. 
    1. Adequate Water Access & Intake 
    2. Optimizing Dietary Metabolizable Protein (MP) Levels: 
      1. Consider increasing MP levels while maintaining the optimal level and ratio of the key amino acids, lysine, and methionine.
    3. Monitoring Energy Intake:
      1. Consider increasing dietary starch/sugar levels without sacrificing effective fiber intake.
    4. Assessing Vitamin & Mineral Supplementation:
      1. Highly bioavailable sources of trace minerals and vitamins are important to combat oxidative stress and enhance immune function.
  4. Dry Period Management: Field research from Cornell University shows that slightly longer dry periods and gestation lengths are correlated to higher colostrum yield. Are your days dry averaging closer to 60 days or 50 days? Dry periods of less than 50 days are associated with lower colostrum yield.
  5. Maternity Management: How long is the dam with the newborn calf? Does this alter the hormonal induction of colostrum? With today’s tight maternity protocols, consideration for if it makes sense to provide extra time for the dam and newborn calf may need to be examined. 



  1. Changes in biomarkers of metabolic stress during late gestation of dairy cows associated with colostrum volume and immunoglobulin content. 2023.  R.M. Rossi, et al. Michigan State University. East Lansing, MI
  2. Epidemiology of bovine colostrum production in New York Holstein herds: Prepartum nutrition and metabolic indicators. 2023. J. Dairy Sci.106:4896–4905  T. A. Westhoff, et al. Cornell University, Ithaca NY
  3. Low colostrum yield in Jersey cattle and potential risk factors. 2018. J. Dairy Sci. 101:6388-6398  K. Gavin, et al. Washington State University, Pullman WA 
Improving Animal Health

Dietary Phosphorus Implications in Transition Cows

Dietary management strategies to improve blood calcium and reduce the risk of milk fever in dairy cows has been extensively studied over the decades. While research has looked at products, work has also focused on evaluating various levels of individual macro-minerals in pre-fresh diets and the impact on a cow’s risk for milk fever. More recently, research has focused on how reducing dietary phosphorus concentrations could help improve blood calcium and reduce the risk of hypocalcemia.

At the 2023 Tri-State Conference, Walter Grünberg, a German researcher, discussed his recent work on restricting prepartum dietary phosphorus content. One of the main highlights was a study that restricted dietary phosphorus (0.16% DM) in close-up dry cows for the four weeks prior to calving. Cows that were fed the restricted phosphorus diet prepartum had decreased blood phosphorus concentrations, while also having significantly greater blood calcium concentrations relative to their counterparts fed a diet adequate in dietary phosphorus (0.30% DM).

Cows fed the restricted phosphorus diet prepartum also had increased markers of bone mobilization. Mobilizing bone is a crucial part of a cow’s physiology to maintain blood calcium as she starts to synthesize colostrum and milk. Bone is a major supplier of calcium during times of extreme demand, such as lactation, due to the large stores of calcium (and phosphorus) found within bone. These signals to mobilize bone in the current study appear to be induced through the presence of low blood phosphorus concentrations, a result of the restricted dietary phosphorus intake. Grünberg’s results indicate that restricting dietary phosphorus content in the close-up dry cow can improve blood calcium status primarily by driving bone resorption.

Grünberg’s research is not the first to show the relationship between dietary phosphorus and blood calcium in the dairy cow. Historically, research has demonstrated that increasing levels of dietary phosphorus results in lower blood calcium concentrations and increased risk of milk fever. This same concept holds true in other species, with work demonstrating that high blood phosphorus concentrations can inhibit vitamin D synthesis. However, a dietary phosphorus restriction large enough to robustly decrease blood phosphorus concentrations and induce bone mobilization to support calcium demand and improve blood calcium at calving had not been studied in the dairy cow until now.

Stay tuned for more on phosphorus restriction pre-fresh and implications on blood calcium —don’t hit the snooze button!


Goff, J. P. 2006. Macromineral physiology and application to the feeding of the dairy cow for prevention of milk fever and other periparturient mineral disorders. Animal Feed Science and Technology. 126:237-257.

Lean, I.J., P.J. DeGaris, D.M. McNeil, and E. Block. 2006. Hypocalcemia in Dairy Cows: Meta-analysis and Dietary Cation Anion Difference Theory Revisited. Journal of Dairy Science 89:669–684.

Rader, J. I., Baylink, D. J., Hughes, M. R., Safilian, E. F., and M. R. Haussler. 1979. American Journal of Physiology. Calcium and Phosphorus Deficiency in Rats: Effects on PTH and 1,25-dihydroxyvitamin D3. 236:118-122.

Wächter, S., I. Cohrs, L. Golbeck, M.R. Wilkens, and W. Grünberg. 2022. Effects of restricted dietary phosphorus supply to dry cows on periparturient calcium status. Journal of Dairy Science 105:748–760.