Supplementary feeding of rangeland cattle

Page last updated: Monday, 23 October 2017 - 11:12am

Please note: This content may be out of date and is currently under review.

Native pastures generally have adequate nitrogen levels during the growing season. During this time phosphorus is the most limiting nutrient. As the grass matures and sets seed, the nitrogen content of the pasture decreases. This can lead to protein and energy deficiencies which result in decreased animal production. Feeding urea during the dry season can increase digestion, resulting in improved animal performance. However urea can be toxic to cattle and so must be introduced slowly. Other important nutrients include calcium, magnesium, sulphur and sodium.

Phosphorus supplements

Grasses are most nutritious during the growing season. At this time there is usually sufficient energy and protein in the diet and phosphorus becomes the most limiting nutrient. The greatest benefit of feeding phosphorus will be realised during the growing season where increased growth rates of up to 40kg can be achieved.

Why feed phosphorus?

Phosphorus is important for a range of metabolic processes including:

  • formation of bones and teeth and a structural component of skeletal tissues
  • absorption of carbohydrates such as glucose through intestinal tissues
  • transport of fatty acids throughout the body
  • metabolism of energy
  • facilitation of fat, carbohydrate and protein utilisation
  • improving efficiency of feed utilisation
  • energy transfer reactions
  • normal milk secretion
  • buffering of body fluids.

Phosphorus deficient cattle have the ability to mobilise phosphorus from their skeleton. This is particularly important for lactating breeders as phosphorus plays a critical role in milk production. As phosphorus content in the skeleton is depleted, cattle are left vulnerable to injuries such as broken bones.

How do I know I should be feeding phosphorus?

Obvious signs of phosphorus deficiency include:

  • bone chewing
  • depraved appetite
  • stiff gait
  • mortality
  • bone fragility leading to breakages.

Less obvious signs include:

  • reduced feed intake
  • reduced milk production
  • reduced fertility.

A blood phosphorus analysis will provide the best indication of phosphorus status in growing cattle, however this is not recommended for lactating cows. If cattle are not already being fed phosphorus a faecal near infrared reflectance spectroscopy (NIRS) in conjunction with a faecal phosphorus analysis can be used.


Contact information

Rebecca Butcher
+61 (0)8 9651 0540