Why is phosphorus important?

Phosphorus is found in all animal tissues and fluids and is involved in many body functions such as energy transfer reactions. Therefore, it affects every activity in the body, including growth and reproduction.

When should phosphorus be fed?
Phosphorus requirements are related to the animal’s intake of protein and energy. When energy and protein intakes are high and allow rapid growth and production (milk and reproduction), (i.e. during the wet season) the need for phosphorus is also markedly increased. In phosphorus deficient areas it is during this period, the wet season, that phosphorus deficiency is most evident and when additional phosphorus (supplements) is most needed.

Phosphorus is less important in the dry season as protein and energy are more likely to be limiting so intakes will be low and therefore the requirement for phosphorus is also low. Animals will show little if any response to phosphorus supplements during this period. There is even evidence that animal performance can be reduced if phosphorus is fed at high levels when nitrogen is deficient.

How much phosphorus do cattle and sheep require?
Cattle require 5 – 10grams/head/day, depending on the severity of the deficiency. Intakes should be at the lower end of the scale during the dry season and at the higher end of the scale during the wet season.

Sheep have a lower requirement for phosphorus as they efficiently utilize phosphorus because they recycle a large proportion of phosphorus, hence deficiency is not commonly seen.

Symptoms of Phosphorus Deficiencies

  • Depraved appetite – animals chew bones, twigs, bark and other strange objects. Bone chewing can also be a habit and be present even if phosphorus is not deficient.
  • Poor growth rates – research results indicate 10 -20% reduction in growth rates
  • Low reproductive rates – calving rates can be reduced by up to 40% on acutely (severely) deficient country.
  • Peg leg – Stiff, proppy gait and arched back.
  • Rough, coarse coats and cattle in poor condition, especially lactating breeders. Soft, weak bones.