Phosphorus

Like Calcium, Phosphorus (P) is a major constituent of bone, making up 14 to 17% of the skeleton.

Function:​​

Like Calcium, Phosphorus (P) is a major constituent of bone, making up 14 to 17% of the skeleton. It has a role in the stability of skeletal integrity : apatite is a calcium phosphate complex and is the primary component of the bone matrix. Phosphorus is important for the acid-base metabolism, the energy transduction and utilization in cells. It is a component of nucleic acids and cells membranes.

Sources:

Plants, inorganic phosphorus in feed supplements.

Daily requirements (NRC, 1989):

Maintenance : 0.028 g /kg body weight (BW). 

Mature horse at training : 0.036 to 0.058 g /kg BW

Never allow intakes to be greater than Ca.   

Deficiency:

Similar to effects of calcium deficiency : Rickets and osteopenia in foals (enlarged joints and crooked long bones), osteoporosis, weakening of the bones and insidious shifting lameness in mature horses. Malfunction of muscles and nervous system.

Excess :

Negative effect on calcium uptake (nutritional hyperparathyroidism), calcium deficiency.

When problems may occur ?

High calcium concentration in the diet depress phosphorus. Furthermore, even if the diet contains adequate calcium, excessive phopshorus intake may cause skeletal abnormalities. It can particularly occurs if horses are fed large amouts of grain-bases feedstuffs such as wheat bran or oats with no calcium supplements, of if horses received forages relatively low in Ca with substantial amouts of oxalates.