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Transitioning dairy cows experience heightened metabolic activity and nutrient demands, making adequate mineral supplementation imperative for supporting their health and performance. You know your springers need a correctly balanced combination of calcium, phosphorus, sodium, and magnesium supplementation during this time, and that the exact requirements will be very much affected by the makeup of the winter diet and the liveweight of the cow. However, many farmers are unaware of the specific functions of these macro minerals, leading them to underestimate their importance.

The functions of macro minerals


Calcium is essential for bone formation, muscle contraction, and nerve function. During transition, dairy cows experience a rapid increase in calcium demand to support colostrum and milk production. Inadequate calcium intake can lead to milk fever, which compromises muscle function, increases the risk of dystocia, and impairs immune function.


Phosphorus is vital for energy metabolism, bone mineralisation, and cellular function. Transitioning dairy cows require increased phosphorus intake to support fetal growth, lactation, and maintenance of metabolic processes. Phosphorus deficiency can lead to production losses, higher infertility, and even clinical deficiency (crawler cows) in their herds.


Sodium is essential for maintaining salt-water balance, acid-base equilibrium, nervous system function, and is the key element for saliva production. Saliva is essential in the primary breakdown of fibre – when the saliva is swallowed it then becomes the primary rumen buffer, ensuring rumen pH is held within its optimal range. Any salt deficiency, particularly during early lactation when rumen function requires large quantities of sodium, can exacerbate metabolic challenges and compromise cow health, productivity, and reproductive performance.


Magnesium plays a critical role in muscle and nerve function, as well as energy metabolism. During transition, magnesium supplementation helps prevent grass staggers (hypomagnesemia), a potentially fatal condition characterised by muscle tremors and convulsions. Magnesium deficiency at any time of the season, but particularly during lactation, can have serious implications for animal health, reducing milk production, and making it harder to get the cow back in-calf.


Chloride is essential in the production of gastric acid in the primary stomach (abomasum), which needs a lot of hydrochloric acid as a key part of the digestive process. It’s also central in maintaining the correct acid-blood balance. Because chloride is absorbed through the intestinal wall directly in the blood, it’s the ideal mineral salt to incorporate into a negative DCAD pre-calving transition blend. 


Sulphur is essential for normal growth and reproduction of bacteria in the rumen. The ideal level of sulphur in the diet is around 0.3% but it’s not uncommon for sulphur levels to be higher than this. Excessive sulphur levels can lead to sulphur antagonism in the rumen, meaning it will interfere with vitamin B1 (thiamine), and can cause some critical deficiencies. It also affects selenium and iodine, which can impact antioxidation as well as thyroid function. 

Although sulphur is beneficial in a negative DCAD transition diet, levels need to be kept within a tight range and calculated taking underlying dietary levels into consideration. 

Consequences of inadequate mineral supplementation

Just as adequate mineral levels have a positive effect on health, production, and milk production, inadequate mineral supplementation will have the opposite effect. 

Common consequences include:

  • Increased risk of metabolic disorders, such as milk fever and hypomagnesemia.
  • Reduced milk yield and quality.
  • Poor reproductive performance, including delayed conception and increased calving intervals.
  • Compromised immune function, leading to higher susceptibility to diseases.

Macro minerals play a pivotal role in setting up transitioning dairy cows for a successful and profitable season. Taking into account all factors, including animal environment, and potential antagonistic mineral reactions, will aid in correct macro mineral supplementation throughout the year. By understanding the roles of macro minerals, you can support your springers’ metabolic processes and physiological functions critical for a successful transition.