No. 44/2005Replaces Farmnote 7/92

When a dairy herd averages over 6,000 L per lactation,understanding its mineral requirements and the possibleneed for mineral supplements becomes important.Lower producing cows should be able to meet theirmineral requirements from well-fertilised pastures andfodder crops.

Mineral deficiencies can cause a loss of appetiteresulting in a depressed growth rate, reduced milkproduction, reduced fertility, metabolic disorders and, insevere cases, teeth and bone abnormalities.

The minerals most likely to cause deficiencies underWestern Australian conditions can be broadly classedinto two categories: major elements and trace elements.

Major elements

Calcium and phosphorusA cow’s needs for calcium and phosphorus are generallyconsidered together, since these major components ofthe skeleton occur in both bone and milk as dicalciumphosphate. The bones act as a reservoir from which thecow can supplement her diet for either element.

Calcium is the most common mineral in animals and isrequired for bones, teeth and milk production.

Phosphorus is important for bone formation and most ofthe metabolic functions in the cow. A deficiency inphosphorus can result in lameness and infertility.

For high producing herds, a balanced intake of calciumand phosphorus is important. A ratio of between 1 to 2parts of calcium to 1 of phosphorus is desirable.However, the actual amount of each in the diet is moreimportant. Table 1 shows the need of each element formaintenance and production in dairy cows.

Mineral requirements of the lactatingdairy cowBy Chris Mayberry, District Veterinary Officer, South Perth

Assuming an 18 kg dry matter intake for the cow per day,this equates to 0.6 per cent calcium and 0.4 per centphosphorus in the total ration.

Table 1. Maintenance needs for calcium and phosphorusin lactating dairy cows

Liveweight (kg) Calcium Phosphorus

500 20 g/day 14 g/day550 22 g/day 16 g/day600 24 g/day 17 g/dayAdd (for production) 3.2 g/L milk 2.0 g/L milk

Example: Calcium and phosphorus intake for a herd withcows averaging 550 kg liveweight, each producing 25 L ofmilk and eating 3 kg barley, 2 kg lupins, 2 kg ryegrassdominant meadow hay and 12 kg of clover/ryegrass pasture

Feed Weight Calcium Phosphorus

Barley 3 kg 1.5 g 8.7 gLupins 2 kg 4.6 g 6.4 gHay 2 kg 6.0 g 4.8 gPasture clover 6 kg 54.0 g 15.6 gPasture ryegrass 6 kg 19.2 g 15.6 g

TOTAL 18 kg 85.3 g 51.1 g

Table 2. Average calcium and phosphorus content of somefeeds (% of dry matter)

Species Maturity % %or part Calcium Phosphorus

Clovers, pasture or haySubterranean clover Mid flowering 1.10 0.26Subterranean clover Hay 0.90 0.24White clover Vegetative 1.10 0.34Grasses, pasture or hayPerennial ryegrass Vegetative 0.43 0.37Annual ryegrass Early flowering 0.32 0.26Annual ryegrass Hay 0.30 0.24Italian ryegrass Mature 0.45 0.11Kikuyu ‘lush’ 0.34 0.29Kikuyu ‘rank’ 0.45 0.25Paspalum 0.19 0.22Phalaris 0.30 0.31Oats Grazed crop 0.23 0.09Feed grainsWheat Grain 0.05 0.29Barley Grain 0.05 0.29Oats Grain 0.07 0.34Lupins Grain 0.23 0.32

For a 550 kg cow producing 25 L of milk the dietaryrequirement is 102 g of calcium and 66 g of phosphorus.

Calcium and phosphorus supplementsFor high producing cows, the phosphorus and calciumrequirements may not be met from pasture, fodder orgrains. A calcium and phosphorus supplement isrequired. You should determine the correct level ofsupplementation of these minerals for each herd and foreach season of the year.

The Chief Executive Officer of the Department of Agriculture and the State of Western Australia accept no liability whatsoeverby reason of negligence or otherwise arising from the use or release of this information or any part of it.

Important Disclaimer

For more information visit our web site www.agric.wa.gov.au

1545/7/05-800 ISSN 0726-934X

© State of Western Australia, 2005

Based on Table 1, the maintenance needs of eachcow would be 102 g/day of calcium and 66/day ofphosphorus. Therefore, each cow would need an extra16.7 g calcium and 14.9 g phosphorus.

Using a mineral supplement with 18 per cent calciumand 8 per cent phosphorus added to the grain mix of 3parts barley to 2 parts lupins, this herd would need35 kg to 40 kg of supplement per tonne of grain to meetthe cows’ phosphorus requirements. Many commercialmineral supplements available have much lowerconcentrations of calcium and phosphorus than this.

HypocalcaemiaHypocalcaemia (milk fever), which may occur in earlylactation, is a calcium deficiency brought about by thesudden demand for an increased amount of calciumbecause of lactation. The incidence of milk fever can bereduced by limiting the intake of sodium and potassiumduring the last month of the dry period. In practice, thismeans avoiding pastures heavily fertilised with potash,especially those receiving run-off from the dairy, andfeeding supplements which contain ‘anionic salts’.Anionic salts are high in sulphur and chloride and maycontain high levels of calcium, magnesium andammonium. These help the cow’s system adjust tomobilising calcium rapidly from the bones andincreasing absorption from the gut, but they are not verypalatable.

Earlier advice to simply limit the intake of calcium duringthe dry period has now been superseded

Trace elementsOf the trace elements that are essential, only deficienciesof copper, cobalt and selenium have been implicated incattle health in Western Australia. Other trace elementsare regularly added to mineral mixes but the evidence fortheir inclusion is not available.

CopperCopper is involved in a large number of importantbiochemical functions in the body. Deficiency can resultin poor growth, anaemia, diarrhoea, fragile bones,lowered milk production, infertility and loss of hair colour.The international recommendation is for a level of 10parts per million (ppm) in the overall diet of dairy cattle.However, both molybdenum and sulphur can influencethe availability of the copper in the ration to cattle.Although south-western dairy pastures commonly havelevels of 6 ppm to 8 ppm of copper, signs of copperdeficiency are rarely seen in cattle.

Copper can be incorporated into mineral pre-mixes andgiven to cows with the grain supplement. The overallration should not contain more than 100 ppm.

CobaltCobalt is used in the rumen to make vitamin B12. VitaminB12 is essential for red blood cell production and isinvolved in ruminant energy metabolism. Deficiency canresult in anaemia and depressed appetite with all its

ramifications such as low production, infertility, harshcoat and susceptibility to disease. Decreases in theincidence of milk fever have been associated withsupplementation of cattle with cobalt or vitamin B12.However, visible signs of cobalt deficiency are rarelyseen in south-western cattle.

The international recommendation is for a level of0.1 ppm in the overall diet. South-western dairypastures vary from being deficient to being adequate.Marginal pastures may become deficient after liming.

• The addition of cobalt sulphate to pasture fertilisersat 250g/ha every second year should preventdeficiency.

• An alternative is to treat each cow each year with acobalt ‘bullet’ that the cow swallows. The bullet lodgesin the reticulum or second stomach.

• Another option is to inject the cow every three monthswith vitamin B12

• Cobalt can also be added to worm drenches; or

• cobalt can be added to the grain supplement as partof a mineral pre-mix.

SeleniumThe international recommendation for selenium is for alevel of 0.1 ppm in the diet. South-western dairypastures commonly have levels of 0.01 ppm. Theclassical sign of deficiency, white muscle disease, israrely seen in cattle. However, research in easternAustralia has suggested that selenium deficiency mayincrease infertility, retention of foetal membranes andthe severity and incidence of mastitis. These researchfindings have not yet been substantiated in WesternAustralia.

Well managed herds with unexplained reproduction ormastitis problems may respond, at least in part, tosupplementation with selenium as follows:

• selenium bullets (two per cow); or

• inclusion of selenium in a mineral pre-mix for additionto the grain supplement; or

• drenching with sodium selenate every three months;or

• application of selenium to the pastures with thefertiliser every second year.

Warning: Copper, cobalt and seleniummust always be used with care, sincethey are very toxic in excess.

Other mineralsOther minerals commonly added to stock licks includeiron, zinc, manganese and iodine. Fluorine usuallyoccurs in the mix as a contaminant. There is no evidencethat any of these elements are deficient in dairy cowsgrazing pastures in this State.