New guide unlocks secrets to phosphorus management

James Nason, 15/11/2012

Principle author Desiree Jackson with the updated guide to phosphorus management.Improving management of phosphorus is considered one of the most economically viable and practical ways for northern producers to unlock meaningful productivity gains.

However adoption rates of phosphorus supplementation, particularly in wet seasons when the most significant benefits can be realised, remains very low.

An important new book about to be launched by northern beef scientists and extension officers with Meat & Livestock Australia funding may help to change that.

The book "Phosphorus management of beef cattle in northern Australia” provides a compelling picture of the economic gains that can be achieved through focusing more attention on improving phosphorus management.

Cattle need phosphorus for almost every function and to make full use of available protein and energy in their diet. However, most soils in northern Australia are deficient in phosphorus, a serious nutritional limitation which reduces the efficiency and profitability of many northern cattle operations.

The book is a revised edition of the previous McCosker and Winks book released on phosphorus feeding in northern Australia in 1994. Since its publication new research on phosphorus feeding and testing has led to changes in management and feeding recommendations.  In 2011 a review by Coates and Dixon suggested recommendations for phosphorus management of grazing beef cattle in northern Australia needed to be modified.

The new book pulls together all existing scientific and practical knowledge on the topic of phosphorus management and combines practical tips, regional case-studies and economic analyses to provide a single, easy-to-follow and up-to-date guide for producers.

Principal author, Queensland beef scientist Desiree Jackson, said there were many immediate benefits for producers in adopting improved phosphorus supplementation management, including reduced breeder mortality, improved weaning weights and reduced age-of-turn off, and enhanced cull cow weights.  

Important longer term benefits include an increase in herd fertility, which leads to surplus females for sale, at heavier weights, and increased gross income. This in turn helps to fund future phosphorus supplementation programs.

She believed there were several reasons for the lack of adoption of phosphorus supplementation to date. These included confusion among producers about the recommendations for feeding, the practical difficulties involved in getting lick out to cattle during the wet and the tests required to determine animal phosphorus status.

Some producers also doubted the economic returns.  However, there is strong evidence that the gains from feeding phosphorus outweighed the costs. In 2009 when phosphorus was at astronomical levels of $1800/t, economic analysis by Bill Holmes of the Queensland Department of Primary Industries still showed a six-fold return from feeding phosphorus.

Key messages contained in the book include:

• The animals that need phosphorus most are growing stock, late-pregnant heifers and cows, and lactating cows;

• Deficient animals respond best to P supplement when their diet has adequate protein and energy. This is why P supplementation is most effective during the wet season;

• Signs of acute phosphorus deficiency include bone chewing, broken bones, peg-leg, poor body condition of breeders and botulism;

• There are no simple diagnostic tests for the P status of cattle. Blood and faecal P are the most useful indicators;

•  If P is fed over the wet season on deficient country:

– young growing stock can increase their growth by 30–40kg/year,
– breeders can increase weaning rates by 10–30pc;

• Deficiency is related to soil P status. As a general rule, where soil P levels:

–  are deficient (5mg/kg or less), all classes of stock are likely to respond to feeding P,
– are marginal (6–8mg/kg), young breeders are likely to respond to feeding P,
– exceed 8mg/kg, the economic benefit from feeding mature cows diminishes.

• Responses to P supplement may be lower if animals running on P-deficient country
have access to adjacent areas of high-P soils, such as frontage country;

• Supplements should be compared on the cost of their P content, on the practicality of feeding out and on whether the animals will be able or willing to eat target amounts;

• A typical wet season loose-mix P supplement should contain at least 8pc P; a typical dry season supplement will contain 2–4pc P and also non-protein nitrogen (eg urea);

• On deficient country, lowering the stocking rate will not reduce the need to feed phosphorus;

• Where the native pasture on deficient country contains sufficient stylo, cattle mayrespond significantly to P supplement during the dry season because of the extra
protein in their diet;

• Because cattle eat more pasture when P supplements are fed, stocking rates should be reduced to avoid overgrazing;

• The economic benefits from feeding P are maximised when done in conjunction with other aspects of good herd management.

Ms Jackson said there was a basic lack of understanding of the fundamentals of nutrition relating to feeding phosphorus in the wet season.

“People get really busy feeding lick supplements during the dry, and as soon as it rains understandably they want a break from placing lick across their property,” she explained.

“And they see their animals gaining weight, and they think they’re quite okay, but what they don’t understand  is the massive opportunity available to capitalise on wet season feeding when protein and energy levels are at their peak.  If there insufficient phosphorus in the diet, animals cannot fully utilise all the protein and energy coming into the diet.

“So they’re missing a big opportunity to put condition on their animals, particularly breeding stock, which improves milk production and weaning weights as well as significantly increasing conception rates.

“During the wet season when phosphorus requirements are at their peak, if animals aren’t provided with sufficient phosphorus supplements they will start to draw on bone reserves to meet their phosphorous needs, but there is a limited amount of time that they can keep drawing on bone reserves and at some stage those bone reserves need to be replenished.”

New information not included in previous versions of the book included advice that phosphorus supplementation went hand in hand with an increase in animal appetite, which producers needed to be aware of.

“When animals are phosphorus deficient it actually significantly suppresses appetite and feed intake drops right back,” Ms Jackson said.

“Conversely, people have to be mindful that when they start feeding phosphorus to animals, their appetite is going to increase and feed intake is going to really go through the roof, so they need to adjust stocking rates, similarly as they do for feeding urea.”

“Phosphorus management of beef cattle in northern Australia” will be officially launched at a function in Barcaldine in central western Queensland on November 20.

Two webinars, accessible through the FutureBeef website, will also discuss the book on November 20 and 21.

For further information visit


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