Preventing milk fever during autumn calving

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With autumn calving only around the corner it is important to remember that the diet and mineral intake of autumn calving cows is often less controlled than in the spring calving herdmates, increasing the risk for Milk fever.

Where an abundance of grass is still available, it is tempting to leave dry cows out at grass, making it difficult to restrict their energy intake and becoming over-conditioned early in the dry period. A forage-only dry cow’s diet also lacks essential minerals, trace elements and vitamins she will need during the transition period to get her off on a good start of a new lactation. The transition period is one of the most stressful and important periods for the dairy cow. There are many physical and metabolic challenges that are triggered directly by the calving event. These include low energy intake (related to dry matter intake (DMI) resulting in negative energy balance), inadequate supplies of nutrients such as calcium, potassium and other electrolytes, and low fluid intake. All of these can contribute to metabolic disorders in the dairy cow, which can have varying degrees of negative effects.

A major transition period problem that occurs because of mineral imbalance during the dry period is milk fever. Milk fever is characterized by low blood calcium levels. Mostly seen in the first few days of lactation when milk production exceeds the cow’s ability to maintain calcium levels from body reserves and uptake from the diet, it can already occur in late-pregnancy when calf growth and colostrum production demand lots of calcium.

Milk fever is directly associated with other metabolic disorders, such as retained placenta, ketosis, metritis, as well as being linked to issues with fertility and somatic cell counts. The cost of a case of milk fever is therefore estimated to be over €300. A case of unseen subclinical milk fever, which is 6 times more likely to occur than clinical milk fever, is approximately €120. Magnesium, Potassium and Calcium are the key minerals that need to be managed to prevent milk fever developing around calving.


1. Body Condition Score (BCS) of your late lactation cows. It is easier to adjust both excessive as well as low BCS while cows are still milking compared to when they are already dried-off. Aim to have cows at BCS 3.25 at dry-off and try to prevent BCS from increasing above 3.5 during the dry period.


2. Mineral supplementation of grazing dry cows. Inadequate mineral intake during the dry period can cause health problems in both cow and foetus. Retained cleanings, (sub-)clinical milk fever, ketosis and displaced abomasum are all disorders that can result from mineral deficiencies and will prevent the cow from reaching her full production and fertility potential during the following lactation. A specific pre-calver mineral and trace element supplement should meet the dry cow’s needs for Magnesium, Copper and Selenium. A forage analysis will provide you with the information on the levels of different minerals and trace elements and allows you to make the right choice of mineral supplement for your herd.

  • Cows coming close to calving need to have low dietary calcium intakes to prevent milk fever. Fresh grass is very high in calcium & potassium, therefore, dry cow intakes of fresh grass should be limited in the weeks before calving and Pre-calver minerals containing no calcium, but lots of the important vitamins and minerals needed to produce a healthy cow and calf should be supplemented. Avoid lush pasture for autumn-calving cows, as this grass is low in magnesium.


3. Pre-calver minerals are essential for autumn calving cows:

  • Suitable pre-calver minerals contain the important major minerals and Vitamins A, D & E.
  • Reduce the risk of milk fever & retained placenta, and the subsequent cascade of diseases
  • Prime the cow’s immune system for the challenges around calving, help ensure a healthy calf & good quality colostrum
  • Essential in the 6 weeks up to calving, especially when cows are dry at grass in the summer/early autumn
  • A bolus is usually not enough to cover the daily mineral requirements pre-calving


4. Freshly calved cows can be supplemented with a source of essential nutrients in the first 24 hrs. after calving to support the transition from the dry period into lactation.


For more information please contact your local Glanbia Ireland representative. 

First Published: 6 September 2021

Tagged with: Dairy

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