Phosphorus (P)

AT A GLANCE:

Phosphorus (P) and Calcium (Ca)


These minerals are the main constituents of bones (98% of calcium is included in bones and teeth, and 85% of phosphorus), but they also function in several chemical reactions within catalysts, particularly those involved in neuro-transmission and muscular contraction.


Both elements must be associated in feed management because their absorption is linked to their ratio in feed and are also dependent on hormonal and vitamin mechanisms. The Ca : P ratio must be between 1,5 : 1 and 2 : 1 depending on the physiological status of the horse.


The raw material diversification, especially regarding calcium, is of major importance in order to improve absorption. Many feed manufacturers add only one type of calcium as calcium carbonate. This form is poorly bio-available and unappetising. 

Phosphorus (P)

Ratio Calcium/Phosphorus: Ca/P


  • Excess of calcium is rarely harmful provided the amount of phosphorus is adequate but it might affect the assimiliation of trace-elements involved in bone growth.
  • Excess of phosphorus can produce problems such as excess output of the parathyroid glands and bone demineralization.
  • Ideal ratio Ca/P : 1.5 : 1 to 2 : 1 but varies according to stage of growth, activity and reproduction.
  • Foal: Ca/P ratio 1.8 : 1
    Mare: lactation, gestation Ca/P ratio should be 1.5 : 1 to 1.7 : 1


Inadequate supplies of calcium and/or phosphorus can affect:


  • Bone mineral structure => skeleton
  • Nervous conduction => reaction times
  • Muscular contraction => performance
  • Enzymatic catalyst => health

  kg Ca (g) P (g) Ratio Ca:P
Requirement   49 27 1.8:1
Oats 5 4 17 0.2:1
Hay 5 21 11 1.9:1
Total 10 25 28 0.9:1
% of requirement   51 104  

Practical example:


a ration of 5 kg oats and 5 kg good hay:


To calculate the ratio of Calcium : Phosphorus