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DEEP DIVE

Calcium and Magnesium - The Facts

Calcium to Magnesium Ratios

Target Cal:Mag ratio for optimum animal performance is between 1.3:1 and 5.8:1 (Cal should always exceed Mag)
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Calcium – The most important nutrient for all classes of sheep and cattle.

Calcium is essential for bone development and milk production, along with affecting muscle contraction (mobility and lambing), transmission of nerve impulses and cardiac regulation. Calcium interacts extensively with magnesium and phosphorus.

Magnesium - Sheep and cattle depend on a daily supply of magnesium due to poor availability in body reserves. It is an essential enzyme activator and benefits smooth muscle function.

Low magnesium (hypomagnesaemia) reduces the effectiveness of vitamin D, which is crucial for calcium absorption in animals, increasing the risk of low calcium levels (hypocalcaemia). 

Excessive magnesium can also decrease calcium absorption, affect bone calcium, and cause calcium loss in urine. 

High amounts of zinc, oxalates, certain metals, fats, and high pH levels in feed can also interfere with calcium absorption. 

The recommended calcium-to-magnesium (Ca:Mg) ratio in animal diets can range from 1.3:1 to 5.8:1. A common target is around 3:1, which helps ensure proper calcium absorption. Suggested minimum dietary levels are 2.4 g/kg of dry matter for calcium and 1.9 g/kg for magnesium, with higher needs for young, fast-growing animals and high-producing dairy cows.

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The Benefits of Supplementing Calcium and Magnesium During Late Gestation and Lactation

Supplementing calcium and magnesium during the critical stages of late gestation and early lactation delivers significant benefits for ewe, lamb, cow and calf performance. These minerals play a vital role in supporting metabolic function, skeletal development, immune health, and milk production, all essential for a strong start to life.

Key benefits include:

Easier lambing due to improved muscle and nerve function
Increased milk production, supporting faster-growing, healthier lambs
Improved weight gain, leading to higher productivity and profitability

According to research by the NSW DPI, Graham Centre for Agricultural Innovation, and CSU’s Fred Morley Centre, targeted calcium and magnesium supplementation has been shown to result in:

0%
more kilograms at marking
0%
more kilograms at weaning

Check the label - Calcium to Magnesium Comparison Tables

The below tables have been developed to analyse if the calcium to magnesium ratio is in the correct range. Using calcium % in the product, eg. if the product that is being analysed has 10% calcium, as per the below table the magnesium content needs to be 1.7% to 8% to be in the correct ratio.
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Using magnesium % of product, eg. if the product that is being analysed has 6% magnesium,  as per the below table the calcium content needs to be 8% to 35% to be in the correct ratio.
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