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Phosphorus helps boost productivity and profitability

30 July 2021

John Grey quote image.png

'Yardoogarra' is on the coast south-west of Broome. The 72,000 hectare property is mostly phosphorus-deficient red sandy loam ‘pindan’ country, with 5,000ha of highly productive marine plain. Breeders are run on the pindan; weaners, heifers and sale cattle run on the coastal plains.

John and Tricia Grey have been on Yardoogarra since 1969. All breeders had some access to good-quality grazing on the coastal plain country up to 1986, after which they were confined solely to the pindan country.

Herd management

Breeders were control-mated each year, bulls in from mid-February to June, from 1990 to 1999. P supplement was introduced to overcome a lameness problem. Control mating was discontinued in 2000.

Excellent cattle records are maintained on Yardoogarra and indicate an average weaning rate of 56%. Female sales as a percentage of total sales averaged over the same period were 44%.


“By the second year on the pindan, it was apparent we had a problem with lameness and thrift in lactating cows,” John said.

“A neighbouring property had similar problems and together we drifted into supplementation starting with salt, urea and MAP–DAP mixes.”

Early on, fertiliser-based supplements markedly reduced peg leg and, although John said cows were certainly stronger at the end of the year, it did not eliminate lameness.

High fluorine

This persistent lameness was eventually diagnosed as damage to smooth surfaces of joints caused by an excess of fluorine. Fluorine in most of the bore waters at Yardoogarra was exacerbated by the fluorine from the MAP–DAP. As a result, John switched to mono di-calcium phosphate (MDCP) as Kynofos™ in 1992.

He started purchasing Kynofos™ in 21.5 tonne container lots, initially delivered by ship to Broome, but later containers have been trucked from Fremantle and off-loaded on the property. Around 10 tonnes of Kynofos™ are fed each year so one container lasts for two years.

The price of Kynofos™ consignments delivered to Yardoogarra in 21.5 tonne container lots increased from $892/tonne in 2006 to $1,334/ tonne in 2009. Because of the price increase, only 10 tonnes were purchased in 2008.

Supplement mixes

High-grade Brahman breeders are run on the pindan country of Yardoogarra at a stocking rate of one breeder per 40 hectares, and are supplemented all year with home-mixed supplements of Kynofos™, salt, urea and sulphate of ammonia. The recipe is varied from time to time to achieve target intakes. Urea is not added during the wet.

Kynofos™ provides 40% of the supplement in the wet season and 20% in the dry season. Supplement is mixed on the station and fed out in troughs as a loose mix every three to four days throughout the year.

When there is green feed (usually December to May), the target intake is 8g P/head/day, but 4g/head/day during the dry. Consumption during 2009 averaged almost 6g P/head/day.

The cost of total supplement fed averaged over the almost six years (2005–2010) (including the high price for P and urea in 2008–09) was around $19.50/breeder/year or $1.60/month, with the phosphorus component costing around $14 a year.

Cattle response

As supplements containing at least some P have been fed for over 20 years, it is not possible to clearly determine cattle performance before P was fed. Records averaged over five years from 1991 (Kynofos™ introduced in 1992) indicated an average weaning rate for that period of around 49%.

These records indicate that while weaning rates are not ‘spectacular’, they are accurate and have improved over time. The percentage of females sold indicates that female death rates are low and reflect effective supplementation and management on the grossly P-deficient pindan country.

“By feeding phosphorus in our pindan country, we have eliminated the problem of lameness in our breeders, and we are confident that cows can now raise a calf and remain healthy.”

Yardoogarra economic modelling

The Breedcow herd model was used to compare the performance of a 1,000-cow herd before and after supplementation. Inputs into this model have been based on animal performance and sale price information provided by John and Tricia Grey at Yardoogarra in 2010 and information and experience from other sources (Table 1).

Modelling assumptions

1. ‘Current performance’ is based on recorded weaning rates, percent female sales averaged for the period 2002–03 to 2008–09, and 2009 turn-off weights and prices.

2. ‘Before P’:

  • weaning rate 49% – indicated from Yardoogarra 1990 records
  • breeder death rate up to 9% – based on female sales and weaning rate
  • female sales as percentage of total sales reduced to 39% – see below
  • prices reduced by about 10% – to reflect lower sale weights of unsupplemented cattle at the same age.

While the breeder death rates ‘before’ are estimates, a recent survey in the Kimberley recorded female sales as 38% of total sales averaged over two years. This indicates that 39% female sales is realistic for P-deficient country in this region.

Breedcow modelling outcomes are summarised in the table below. Results are presented as a fixed number of breeders (1,000 head) and as adult equivalents (AE) in each of the before P and after P scenarios. AE represents the same stocking pressure from the slightly different herd compositions resulting from a more efficient, supplemented herd.

While the exact economic response to supplement is difficult to determine accurately, the response in the gross margin (approximately 25% increase per 1,000 breeders) indicated by the Breedcow modelling confirms the opportunity to improve enterprise profitability on P-deficient country.

Table 1. Modelled response to P supplement at Yardoogarra


No P Supp

+ P Supp

AE + P Supp

No. of breeders








Wean %








Females sold




Males sold




Female sales %




Female sale price




Male price




Net sales




Direct costs (excluding bulls)




Bull replacement




Gross margin




$ response to P