How important is Phosphorus?

Please consider the following points and the need for Phosphorus in your feeding program.

Of concern is when graziers in phosphorus deficient regions reduce phosphorus levels in their loose lick in winter months to save money but then don't supplement phosphorus in the wet months again to save money. The end result being that cattle are without supplementary phosphorus all year round.

Phosphorus is the second most plentiful mineral in the body after calcium.
P combines with calcium in the formation of bones and teeth.
About 99% of the Ca is contained in the skeleton where the Ca:P ration is about 2:1.
Ca and P are constantly being withdrawn from bones and replaced.
P is lost in faeces (a 400kg animal could lose up to 8gP a day) and in milk (up to another 5gP per day) during lactation.
Its most important roles are the conversion of feed into energy and the build-up and repair of body tissues.
In addition, pregnant cows must supply P to the developing foetus, and after calving these cows require additional P for the production of milk.
The most common mineral deficiency in grazing animals is likely to be phosphorus,
Cattle with this deficiency will perform better if supplemented with phosphorus when gaining weight during the wet season,
P supplementation will increase feed intake where nitrogen concentration in feed exceeds 1.3%.
Studies have shown feed intake can increase by between 12 and 61%.
Treat phosphorus like a growth promotant, that is, it will improve growth rate only when cattle are already gaining weight.
Feed it during the period of active pasture growth,
Signs of deficiency include poor cattle performance on growing pasture, broken bones, cattle chewing bones (at risk of botulism) or signs in the country termite mounds, sandy soils, spotted gum, wattle and mulga.
Where possible trial a group with P feeding and measure the results against a group not receiving additional P supplementation.
Response in breeders can take up to three years to yield results. Note: Supplementation of P-deficient cattle with P will increase feed consumption, branding rate and growth rate. All these outcomes will result in an increase in grazing pressure on pasture however it offers the chance to increase sales.
P Supplementation will give responses only when levels of other nutrients in the diet, particularly nitrogen and energy, are adequate and P is the factor limiting performance. This is the case in the early wet season.
Do not feed P to cattle when losing weight.
A ration of calcium to P of 1:1 is recommended as plants generally have a higher level of Ca than P.

Recommendation

Supplement all stock in a herd with an ‘acute’ status. Gross margin gains will be high.
Supplement all stock in a herd with a ‘deficient’ status. Economic returns will be lower than with an ‘acute’ deficiency but will still be attractive.
Supplement only first-and second- calf lactating breeders in ‘marginal’ country. It may pay to supplement young steers in the more ‘marginal’ country in a good year when they have a high rate of gain.
Reduce the herd numbers below pre-supplement stock numbers to account for increased DM intake.
Where deficiencies exist, P supplementation has an effect on breeder mortality, branding rate, heifer mating age, growth rate of steers, turnoff weight of steers and surplus females and the ratio of male to female sales.