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This article was published in 1995
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Phosphorus Deficiency
Michael Hindmarsh, District Veterinarian, Condobolin Rural Lands Protection Board
Phosphorus is critical for the correct nutrition of cattle. It is the second most plentiful mineral in the body after calcium. Each litre of milk contains 1g of Phosphorus.
The ancient Australian soils are low in Phosphorus with grain cropping, erosion and animal sales removing Phosphorus from the farm.
Available Phosphorus varies in the soil and rapidly decreases as plants mature. The challenge is maintaining the cows Phosphorus status throughout the year.
Eighty per cent of the body's Phosphorus is within the bones and teeth. This reservoir is used to maintain normal valves within the blood. The ends of the long bones, ribs and sternum are the source for Phosphorus extraction and consequently are first to fracture.
Clinical signs
Phosphorus deficiency is indicated by poor appetite, low growth rates, a coarse, dull coat, poor fertility, bone chewing in cattle, soil eating in sheep, 'peg leg', 'creaky cows' and the occurrence of broken bones.
Diagnosis
A range of tests have been evaluated to determine animal and herd Phosphorus status. The best methods are: -
1. Tail vein serum samples
Tail vein clotted blood samples are collected from at least 10 cows. The serum is harvested using clot retracing Vacutainers. Testing for inorganic Phosphorus is carried out on fresh or frozen serum.
2. Faecal Phosphorus
A draft of 20 COWS or heifers are selected being of same breed, age, pregnancy or lactational status. A tablespoon size sample of manure is collected from each and mixed together, then sun dried on a piece of iron. The dried manure sample is then milled and tested for Phosphorus.
The result from the above two tests then allows the selection of: -
1. Severe cases with low blood and faecal Phosphorus. These females will have reduced bone density and respond quickly to supplements when growing.
2. Moderate cases with normal blood and low faecal Phosphorus.
3. Adequate with normal blood and normal faecal Phosphorus.
Supplements
Boosted Phosphorus licks are the best supplements for severe deficiency as cattle need up to 5g of Phosphorus per day. Blocks can only supply about 2g of Phosphorus per day. Water treatments are useful where no alternative water supplies exist.
The best Phosphorus supplements are KYNOFOS, BIOFOS or DICALCIUM PHOSPHATE. A typical lick is composed of Kynofos 400 parts, limestone 200, salt 250, sulphur 5 and molasses 100. These ingredients are mixed together and poured into the bottom half of a 200L drum.
Toxicities
Severe bone fractures have occurred during supplementation with some rock Phosphates and mono-ammonium phosphates. This is caused by Fluorine contamination. Other potential toxicities are from Cadmium and Mercury.
Lick strategy
The only time to successfully correct Phosphorus deficiency is supplementation when the animals are actively growing. This treatment restores the Phosphorus deficits within the spongy bone. Therefore, the treatment window is limited to spring and autumn flushes or to grain feeding periods.
Summary
Phosphorus deficiency is poorly understood in Southern Australia. Surveys at Condobolin show widespread bone and soil chewing and a scattered prevalence of bone fractures in cattle which show no blood phosphorus. Supplementation with phosphorus will be a positive treatment to the challenge of Anthrax infection. The Meat Research Corporation and Queensland DPI have produced an excellent booklet 'Phosphorus Nutrition of Beef Cattle in Northern Australia' 0194912 Price $35.00.