Phosphorus supplementation of cattle in northern Australia

Diagnosing a phosphorus deficiency

Developing a phosphorus management plan

BotulismEconomics of phosphorus supplementation

Breeder management  |  Effect on productivity

Depletion and repletion  |  When to supplement with phosphorus

Choosing the right supplement  |  Managing intake

Lick shed examples  |  Help

Phosphorus deficiency is a major problem for grazing cattle in much of northern Australia because of the low soil phosphorus levels in many soils. Whilst phosphorus is important in all bodily processes, the major impact of phosphorus deficiency in cattle is a significant reduction in appetite. This results in lower pasture intake and consequently lower energy and protein intake.

The reduction in nutrient intake affects the breeder’s ability to maintain body condition, resulting in lower weaning rates and increased mortality. Milk production is also reduced leading to lower weaning weights. In growing cattle, the lower nutrient intake produces lower growth rates. All of these impacts have serious consequences for production and profitability.

Other symptoms of phosphorus deficiency include bone chewing (increases the risk of botulism), chewing of other objects (rocks, sticks, wire, etc.), stiff gait, peg leg and bone breakages.

Watch this six minute video summarising the issues phosphorus deficiency causes in a herd, signs of phosphorus deficiency and the production gains that can be made as a result of supplementation:

The webinars below provide more information on phosphorus requirements and supplementation of breeders and growing cattle:

How to diagnose phosphorus deficiency

It is important to know if a specific mob or paddock is phosphorus deficient and if cattle will respond to phosphorus supplementation. There are a variety of ways to assess whether phosphorus deficiency is a problem.

  1. Observation – symptoms of phosphorus deficiency in cattle are described above.
  2. Soil and pasture tests – soil and land type mapping and information can give an indication of the potential for a phosphorus deficiency. See the Land types of Queensland page for more information. Soil and pasture tests can determine the phosphorus concentration in the soil and plants, however they are of limited value because most grazing paddocks contain a mixture of soils and land types. The selective grazing of cattle means that simply testing the available plants is not representative of the diet consumed.

Watch this webinar for more detailed information on diagnosing phosphorus deficiency:


Develop a phosphorus management plan

Developing a phosphorus management plan for a property starts with understanding the relative productivity and phosphorus status of land types within paddocks. Click here to view a phosphorus management plan with examples. Or click here to download the editable template to make your own phosphorus management plan.

Land type mapping is an invaluable resource for property planning and herd management. Land type maps can be obtained using FORAGE or Qld Globe and land type information is located.

Phosphorus management has an overall effect on the management of a herd and the timeliness of operations like moving cattle, weaning, joining period, supplement delivery. You can use something like this example herd management calendar to plan your year. Or click here to download the editable template to create your own herd management calendar. 


Botulism is a progressive paralysis from the ingestion of toxin produced by Clostridium botulinum which is found in bones and carcases. It is the most significant cattle health risk over much of northern Australia and prior to botulism vaccines being available was responsible for large losses annually. Cattle in phosphorus deficient country are at risk of ingesting the toxin because the depraved appetite caused by phosphorus deficiency leads to animals eating bones and carcases. Severe protein deficiency can also cause a depraved appetite and botulism.

Fortunately, the ready availability of highly effective vaccines means losses can be prevented. Some vaccines require only a single dose to achieve immunity rather than the traditional two doses. Most products provide protection for 12 months, but a product with three years’ protection is available. The choice of product should be based on ease of use in the property management program. Ensuring animals receive booster doses is critical for herd protection to be maintained.

Feeding supplements will reduce the likelihood of cattle chewing bones but will not eliminate it, as it is a learned behaviour, therefore botulism vaccination is always required on phosphorus deficient country.

Economics of phosphorus supplementation

Economic analyses and producer case studies demonstrate that phosphorus supplementation in deficient country is a very cost effective strategy for beef businesses. More information on the latest phosphorus economics and the benefits modelled for beef businesses in the Fitzroy region of Queensland and the Katherine area in the Northern Territory can be found in an article written by Dr Maree Bowen (Department of Agriculture and Fisheries Principal Research Scientist) and Fred Chudleigh (Department of Agriculture and Fisheries Principal Economist), “Improving beef business performance with phosphorus supplementation“.

Breeder management

Lactation significantly increases the phosphorus requirements of breeders, therefore weaning management is an important component of managing phosphorus deficiency. Timely weaning of breeders and if appropriate, early weaning, enables breeders to better cope with low phosphorus pastures. The reduced requirements for energy, protein and phosphorus as a result of weaning can markedly improve body condition.

Calving at the most suitable time for the region and avoiding cows lactating for long periods in the dry season will also mitigate the effects of low phosphorus diets. Where controlled mating is not feasible, breeder segregation systems can enable out of season calving cows to be better managed.

For more information about the nutritional management of breeders, including managing the breeder body condition score to maximise reproductive potential, click here

Effect of phosphorus on the productivity of the breeder herd

A research project at the Victoria River Research Station (Kidman Springs), NT, has found a substantial effect on the productivity of breeders when they do not have adequate phosphorus in the diet. Cows supplemented with phosphorus showed increased reconception rates and produced heavier weaners. Read more about the “Effect of phosphorus supplementation on Brahman females at Kidman Springs” project, including the latest project update.

Cattle consume loose phosphorus supplementation

Phosphorus depletion and repletion

Cows on phosphorus deficient country mobilise phosphorus from their bones and into their blood to make milk for a calf – every litre of milk uses about 1.5 g of phosphorus! Repletion of this bone phosphorus is critical to the reproductive capacity of cows. Supplementing cows with phosphorus and good weaning practices are essential for meeting a cow’s daily requirements and helping them replete their phosphorus bone reserves. Repletion of phosphorus happens very quickly – within days of weaning and supplementation. Recent work conducted by the University of Queensland has also determined that depletion of phosphorus in growing steers happens over about six weeks, after the diet has changed from phosphorus adequate to phosphorous deficient. This is important to consider when moving cattle between different types of country. For more information on phosphorus depletion and repletion in breeding cows and growing steers, watch these two short webinars (20 mins each):

When to supplement with phosphorus

In the wet season when energy and protein levels in grass are at their peak, phosphorus is the first limiting nutrient on phosphorus deficient country. Correcting this deficiency in the diet allows cattle to increase their intake of energy and protein from the grass, meaning there are huge productivity gains to be made in supplementing with phosphorus in the wet season. The challenge for most producers is getting cattle to eat a supplement when there is green grass everywhere.

Because of the high phosphorus requirements for late pregnancy and lactation, phosphorus should be included in dry season supplements for breeders in deficient country as they have the ability to replete their phosphorus reserves, even in the dry season.

Choosing phosphorus supplements

Phosphorus  can be fed to cattle in the form of loose licks, liquid supplements, blocks, or via water medication. Supplements need to be assessed on the cost of supplying the nutrients required, infrastructure requirements and the practicalities of feeding. A critical component of supplement selection and management is ensuring that the required nutrient intakes are achieved in the most cost effective manner. Consequently, the palatability of supplements is an important consideration and may require changes to achieve the target intake.

The principal sources of phosphorus in supplements are:

  • Di-calcium phosphate (DCP)
  • Mono di-calcium phosphate (MDCP)

Each method of supplying nutrients to cattle has both positive and negative aspects that may also impact the supplement strategy chosen. Here are some of the pros and cons for popular phosphorus supplementation methods:

Loose licks

  • Low cost/kg phosphorus
  • Recipe can be customised to achieve target intakes
  • Need shelters in wet.

Liquid supplements

  • Adding P supplements (i.e. MDCP/DCP) to molasses can be a useful strategy where target intakes are hard to achieve
  • Technical grade mono ammonium phosphate (MAP) can be added to roller drum and dunder mixes. Technical grade product has to be used because fertiliser grade products can contain unacceptable levels of fluorine and/or heavy metals.

Wet season blocks

  • High cost/kg phosphorus
  • Weather resistant
  • Easy to distribute before wet
  • Composition cannot be changed once purchased
  • Target P intakes are often not achieved.

Water medication

    • Uniform intake across mob
    • Alternative watering locations in the wet season (e.g. creeks) can make achieving target intakes difficult
    • Water quality can present problems with medicator operation.

Managing phosphorus intake

It is important to know the phosphorus supplement requirements of the classes of cattle at different times of the year on the property’s land types. More information on cattle phosphorus supplement requirements can be found in the “Phosphorus management of beef cattle in northern Australia, PDF 2.2 MB)” handbook.

Feeding phosphorus in the wet season can be challenging. To achieve target intakes, time has to be invested in identifying the most suitable phosphorus source and supplement composition and training animals to eat supplements.

Guides for intake targets are listed in the table below, taking into consideration class of animal and level of phosphorus deficiency.


Table 1. Recommended supplementary phosphorus intakes for different classes of cattle and levels of phosphorus deficiency (Phosphorus management of beef cattle in northern Australia, MLA 2012).

Class of animal Weight (kg) Target weight
gain`` (kg/day)
Recommended supplementary P intake (g/hd/day)
Acutely deficientDeficientMarginally deficient
Steers & heifers200021Nil
Steers & heifers2000.3431
Steers & heifers2000.6641
Steers & heifers2000.9852
Steers & heifers2001.21072
Steers & heifers400-0.32NilNil
Steers & heifers4000321
Steers & heifers4000.3541
Steers & heifers4000.6752
Steers & heifers4000.9962
Steers & heifers4001.21183
Pregnant breeders *400-0.3321
Pregnant breeders *4000531
Pregnant breeders *4000.3741
Pregnant breeders *4000.6962
Lactating breeders +400-0.3752
Lactating breeders +4000962
Lactating breeders +4000.31172
Lactating breeders +4000.61283
`` Target weight gains are the potential daily weight gain based on the diet quality when P is not limiting.
* Late pregnant breeders, last three months of pregnancy.
+ Lactating cows, producing 5 kg milk/day.

Good supplement intake records are critical to ensure target phosphorus intakes are achieved and for managing the cost of supplementation. Download our lick intake calculator here:

Lick shed examples

Scroll through the thumbnails below to see some examples of home-made lick sheds. Lick sheds prevent lick being spoiled and ensure cattle have access to lick in wet conditions when paddock access may be a problem. Lick sheds also reduce the risk of dry season licks containing urea becoming wet and pools of toxic water forming in the trough.

Help with managing phosphorus

Our FutureBeef staff are here to help! Contact your local extension officer to talk about your phosphorus management plan.

Other resources


Visit Meat & Livestock Australia’s Phosphorus hub to download a copy of the updated P Manual – Phosphorus management of beef cattle in northern Australia (second edition) – which offers evidence-based solutions and recommendations on how to assess and address the risk of P deficiency in cattle.

Images supplied by Bernie English and Joe Rolfe.

Information compiled by Kylie Hopkins and Mick Sullivan, Extension Officers, Queensland Department of Agriculture and Fisheries.