Phosphorous Levels, Dry Cow Requirements and Care with Mineral Binders

Phosphorous is essential for the formation of bones and bodily processes.  29% of total mineral content of a ruminant/monogastric is made up of Phosphorous.  As the pie chart indicates 80% is stored in the bones, whilst the remaining 20% is involved around the body in red blood cells and body tissue.

Generally, FYM incorporation means soil Phosphorous levels are high and most dairy feeding include a good supply of Phosphorus.

The richest sources are generally grains and by-products, whilst forages are low, particularly wholecrop and maize silage.  Autumn block dry cows on standing hay or grazing dry cows NOT supplemented with concentrate/dry cow minerals are particularly susceptible to inadequate Phosphorous supplies.  Soil PH also has a bearing on both groups; <5.5PH and grass uptake of Phosphorous is compromised.

Phosphorous intake is affected particularly by Calcium, Magnesium and Molybdenum levels but also Manganese, Zinc, Copper, Iron and Aluminium.  The main aim is to have a 2:1 Calcium:Phosphorous ratio in the body. 

Some Binders on the market do tie up both Calcium and Phosphorous which is the intention, however this is to deal with an excess of one or both.  The reason why some solutions which were working but now do not, is due to a change in the background minerals.  Binders are to lock up an excess but when an excess is not present, they lock up the required amount of a mineral, even a dry cow has a small demand for both Calcium and Phosphorous.  I have seen issues with Phosphorous and Magnesium and “downer cows” where binders are incorrectly balanced.  A key requirement when feeding binders is to feed a dry cow mineral to fill any voids.

This is a very complicated topic/interaction which I have tried to simplify in the above article.

For further information, please contact Wesley at or your local FCG office.

Posted in Arable & Crops, Chippenham, Dairy & Forage.