Minerals and vitamins
Rumen microorganisms and the host ruminant animal require macro and micro minerals, and vitamins for normal growth and development. Grazing cattle generally satisfy most of their requirements for minerals and vitamins from pasture. One notable exception in northern Australia is phosphorus (P) with around 70% of the area considered to be phosphorus-deficient to some extent. Other mineral deficiencies are generally isolated to specific areas of northern Australia.
Cost-effective supplementation programs address the primary limiting nutrient first. Animal performance will be limited by the availability of the most limiting nutrient, and supply of other nutrients will have little or no effect until this is corrected. When protein and energy are adequate, a deficiency of a mineral such as phosphorus will limit animal performance.
Diagnosing a deficiency can be difficult and often requires some assistance to determine the correct testing procedures and to interpret results. The information here is intended only as an overview and it is recommended that professional advice be sought in both the diagnosis and correction of deficiencies.
The minerals required in the diet of cattle can be divided into two groups:
- Major minerals (needed in grams per day or percentage dry matter intake), such as phosphorus, calcium, magnesium, sodium and sulphur.
- Trace minerals (needed in mg/day, or ppm), such as copper, cobalt, and selenium.
Phosphorus is the most significant mineral deficiency in northern Australia. The types of country where deficiency can occur are:
- sandy red and yellow earths
- sandy eucalyptus forest/tea tree country
- spinifex and antbed country
- northern black soil downs (Gulf of Carpentaria)
- other areas not yet identified through testing.
Phosphorus concentration in grass is higher during the summer pasture growing (wet) season but the effect of phosphorus deficiency on cattle performance is greatest, and the response to phosphorus supplementation most effective, during the wet season. The increased protein and energy in the diet during the wet season promotes animal growth and production. Phosphorus requirements for animal production are closely related to protein and energy requirements, a deficiency of phosphorus in the diet when protein and energy are adequate will limit animal performance, i.e. phosphorus is the ‘limiting nutrient’.
Phosphorus is such a significant mineral deficiency of northern Australia that a separate page focusing solely on phosphorus (see Phosphorus nutrition of beef cattle in northern Australia) is available on this site.
Calcium (Ca) and P are closely linked in animal metabolism and the symptoms of calcium deficiency are similar to symptoms of phosphorus deficiency. A deficiency in calcium will also cause poor bone growth. Cattle need 1.9–4g of calcium per kilogram of dry matter.
Calcium deficiency is rarely a problem in northern Australia. Pastures are usually much higher in calcium than phosphorus; and the calcium content of plants declines at a much lower rate than phosphorus as grasses mature. Calcium deficiency in Australia is most commonly associated with pastures containing oxalates (e.g. buffel grass) which make calcium less available to horses (‘big head’ disease in horses).
Because calcium and phosphorus are closely linked, high levels of calcium can inhibit the uptake of phosphorus. High levels of calcium in the diet also interfere with the mobilization of phosphorus from the bones of cattle on low phosphorus diets.
- Ground limestone should not be used to ‘bulk up’ a lick, or used as an intake limiter in loose mix phosphorus-based supplements. Too much calcium can interfere with the uptake of phosphorus.
- Stylo-based pastures have high calcium concentrations which can exacerbate the effects of a phosphorus deficiency. Stylos alone may supply 50% more calcium than an animal needs, without adding the calcium into the diet from supplements. Phosphorus supplementation is recommended for cattle grazing stylo pastures growing on low and marginal phosphorus soils.
- Molasses is relatively high in calcium and only phosphorus should be added to molasses-based production mixes.
- Calcium should be added to feedlot and grain mixes to balance the calcium-phosphorus ratio within the range of 1 calcium:1 phosphorus to 2 calcium:1 phosphorus.
Magnesium (Mg) is needed for a number of reasons, but mainly for bone formation. Magnesium requirements are related to calcium and phosphorus requirements. Cattle need 1.9g of magnesium per kilogram of dry matter.
The symptoms of magnesium deficiency include reduced feed intake, reduced body condition, and reduced milk production. When magnesium deficiency is severe, animals will develop hypomagnesia or grass tetany (i.e. irritability and convulsions followed by death, if not treated). This is predominantly a problem observed in southern Australia, often seen in old cows in early lactation, grazing green grass dominant pasture with high potassium levels.
Excess magnesium can potentially be a problem as it can induce a phosphorus deficiency and reduce dry matter intake. Water from some bores may be high in calcium and magnesium salts.
Sulphur (S) plays an important role in cattle nutrition. It is an important constituent of protein and is essential for microbial activity on protein, cellulose and starch in the rumen. Sulphur is a necessary component of amino acids that are building blocks of proteins. Therefore sulphur plays an important role in protein, fat and carbohydrate metabolism. Cattle require 1.5g of sulphur per kilogram of dry matter.
For grazing cattle the main source of sulphur is in grass, especially when it is green. As pasture matures and the protein content of the grass falls, the intake of sulphur also declines. Sulphur deficiency causes reduced appetite due to reduced rumen microflora and rumen function.
Basalt soils in North Queensland, plus some other major soil types, are known to be deficient or marginal in sulphur with good plant responses to sulphur application recorded. Liveweight responses in breeders and growing cattle grazing on basalt soils and supplemented with a combination of sodium (Na) and sulphur during the growing season have also been recorded in the Charters Towers (Queensland) area. Sulphur and sodium have been identified as the nutrients likely to be limiting animal production when protein and energy are adequate during the growing season on basalt-derived soils.
The recommended supplement on basalt country for wet season salt and sulphur feeding is salt and 12% sulphur by weight. Depending on the location cattle will consume 50–60g of the mix per day. Intakes may be higher than this in the first few weeks of feeding.
Adding sulphur to supplements
Sulphur is required by the rumen microbes to form microbial protein. The animal’s requirements for sulphur are usually met from pasture but when a source of nitrogen such as urea is added to the diet extra sulphur is usually required. This is usually done by adding Gram-Am® (24% sulphur 20% nitrogen fertiliser) or elemental sulphur to achieve the optimal nitrogen-sulphur ratio of urea-based supplements of 10 nitrogen:1 sulphur.
The optimum ratio of nitrogen to sulphur for licks is 10 nitrogen:1 sulphur. This can be achieved by adding Gram-Am or elemental sulphur at the following rates:
- Gram-Am: 1 part Gram-Am to 5 parts of urea by weight.
- Elemental sulphur: 1 part sulphur to 20 parts urea by weight.
If the lick contains a significant amount of protein meal further adjustments may be needed to balance the nitrogen-sulphur ratio at 10 nitrogen:1 sulphur.
Commercially available supplements such as blocks or dry licks usually have the correct nitrogen to sulphur ratio.
Molasses contains significant levels of sulphur so under no circumstances should ammonium sulphate be added to molasses-based mixes even when urea.
Some water, especially bore water, can contain high levels of sulphur.
Can cattle consume too much sulphur?
There have been cases where deaths have occurred when ammonium sulphate was added to molasses mixes, and ammonium sulphate and/or magnesium sulphate was added to grain mixes, in an attempt to reduce intake.
As ammonium sulphate is very bitter it is sometimes included at high levels in dry licks to help to control intake. Excess levels of sulphur have been shown to result in reduced feed intake and reduce rumen motility. Excess sulphur also decreases copper (Cu) retention, precipitating a copper deficiency where copper may be marginal. It is safer to use recommended ratios i.e. 10 nitrogen:1 sulphur or work on 1.5g of sulphur per kilogram of dry matter intake.
Sodium (Na) is an essential macro element. In mammals, it plays a vital role in maintaining the osmotic pressure of body fluids (including blood) and the correct fluid balance in tissues. Sodium is a plasma electrolyte (92% of alkalinity) and is necessary for amino acid and glucose transfer across the cell membrane. Sodium is also essential for the survival and growth of rumen bacteria in cattle and sheep.
Large quantities of sodium are found in the rumen liquor and these can be used by the animal to make up for any short-term (70 to 100 days) deficiencies in the diet. Sodium is an essential component in milk. The mammary glands (udder) can’t secrete milk unless there is sufficient sodium in the diet. One of the first effects of salt deficiency in lactating cattle (beef as well as dairy) is reduced milk output.
The signs of sub-clinical sodium deficiency are similar to those associated with phosphorus deficiency, such as poor growth rates and decreased intake, low branding rates, rough coat, weak-looking weaners and older cattle, and evidence of depraved appetite. This will include bone-chewing and eating soil. As the deficiency gets worse, affected cattle often will lick anything that has a salty taste. In more severe cases water intake and urine output rises, cattle can collapse and suddenly die.
Sodium deficiency results from low sodium intake from both plants and water. Surface waters are usually quite low in sodium, often being less than 20mg/L (20ppm). Similar levels can be found in shallow, pumped bores but these can easily increase up to 500ppm or more during dry/drought periods. Water analysis is essential. On some land types, bore water can be a significant source of sodium.
Plant sodium levels can be extremely variable, with pasture species classed as high, low or variable sodium accumulators. It is difficult to determine soil sodium status as levels can be variable and it can be difficult to get a repeatable reading from the same site over time.
Correcting a sodium efficiency is achieved through feeding dry licks containing high levels of salt. On basalt soils, feed salt and 12% sulphur by weight in the wet season.
Requirements for sodium
|Sodium||Percentage of dry diet||g/day|
|Growth – weaners||0.06%||2.4g|
|Lactation – breeders||0.15%||12g|
Potassium (K) has a number of functions, including, facilitating the uptake of glucose and neutral amino acids to cells and maintaining the acid-base balance in the body. Cattle require 5g of potassium per kilogram of dry matter.
Potassium deficiency is not usually a problem in grazing situations. A deficiency causes:
- growth retardation
- unsteady gait
- overall muscle weakness
Excess potassium interferes with magnesium absorption, so the nutrient balance is important. The high potassium level found in molasses can be balanced by adding 1% salt to molasses mixes.
Copper and selenium
Both copper (Cu) and selenium (Se) play a role in the growth and repair of tissues and in the conversion of carbohydrates into energy. Copper and selenium are essential trace elements for cattle. As the name implies, trace elements are only required in minute amounts (e.g. milligrams – one thousandth of a gram). Cattle require 7–10mg of copper per kilogram of dry matter and 0.1mg of selenium per kilogram of dry matter.
Clinical copper and selenium deficiencies are not common under grazing conditions, but can be common on some coastal country and on marine plains areas. Copper deficiency can develop in improved pasture situations where there are high nitrogen and selenium levels, and copper is in the form of insoluble copper sulphide which is unavailable to the animal. Excessive soil levels of molybdenum can also induce a secondary copper deficiency.
In young animals, deficiency signs may be no more than dull, rough coats and poor growth. Copper deficiency often produces a yellowing of the coat colour in red cattle, but so too can phosphorus deficiency. Copper deficiency has also been shown to be responsible for a greying of the hair tips. Diarrhoea may occur in both young and older cattle with severe copper deficiency. Severe copper deficiency will cause death, particularly in calves.
Severe selenium deficiency produces ‘white muscle’ disease which can result in death. Usually this is restricted to young cattle (under six months) but there are anecdotal reports of death in older cattle. Severe deficiency seems to be associated with reduced fertility in breeders, presumably due to embryonic death soon after conception.
Cattle can store some copper and selenium in the liver, so there may be a deficiency for part of the year, but animal status is adequate for as long as there are stores in the liver (a few months). This depends on level of deficiency, and it may be the reason why sometimes there is no response to supplementation, despite low blood levels.
Before starting on any broad trace element supplement program:
- carry out appropriate testing and seek professional advice
- examine the responses being claimed
- determine the benefits and costs in your situation.
Copper and selenium can be supplemented in several ways:
- Trace element mixtures (often incorporated into both home-made and manufactured mineral supplements). May be variable intakes.
- Injectable copper and selenium preparations. This method is time-consuming and not necessarily without complications, especially with copper. Retreatment is often required at 12 weeks.
- Intra-ruminal trace element boluses. Each animal is treated and the treatment will be active for an extended period – up to eight months or longer (six months for selenium).
There is evidence to suggest that unwarranted use of selenium can aggravate the very problems it is supposed to cure so inclusion of selenium into supplement formulations should generally be avoided.
Cobalt (Co) is another trace element which cattle need in minute amounts (0.10mg of cobalt per kilogram of dry matter). A deficiency can result in loss of appetite, weight loss and a pale coat.
Fortunately cases of cobalt deficiency in cattle in northern Australia are rare. Both cobalt and copper deficiency occur at Julatten (north of Mareeba) on a patch of grey sandy soils. Rumen bullets are used to correct the deficiency in this instance.
Vitamins are not usually a problem with grazing cattle in northern Australia as most vitamins are synthesized by rumen microorganisms. The exceptions are vitamins A and E which are readily available in high quality forage, but may become limiting during extended periods without green feed.
Vitamin A is stored in the liver but after prolonged dry periods, vitamin A stores become depleted. This seldom occurs where cattle are in forest country or have access to browse because the green leaf will supply an adequate amount of vitamin A.
The first sign of vitamin A deficiency is often picked up when cattle are loaded at night time. This is because vitamin A causes night blindness. Other signs are a rough coat, reduction in fed intake and joint oedema. Vitamin A deficiency in cows during early pregnancy can affect the development of their calf’s brain in utero resulting in calves dying soon after birth.
Vitamin D is synthesized by exposure to sunlight, just like in humans.
Cattle can get a vitamin deficiency that is induced by, or associated with, a deficiency in a mineral, e.g. a deficiency in cobalt induces a deficiency in vitamin B12. Low vitamin E levels may be associated with a selenium deficiency when pastures are dry.
- Seek professional advice in both the diagnosis and correction of deficiencies.
- Determine the benefits and costs in your situation.
- Both deficiencies and excess can cause problems.
- With the exception of a few recognized areas trace element and vitamin deficiencies in grazing cattle are uncommon in Australia.
Felicity Hamlyn-Hill, formerly Queensland Government.