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Trace Element Requirements in Deer


There are seven trace minerals that have been shown to be essential in supplementing animal diets. They are Copper, Iron, Zinc, Manganese, Cobalt, Iodine and Selenium. Sub-clinical trace mineral deficiencies occur more frequently than recognised by most deer managers. This is a bigger problem than acute mineral deficiencies because the deer manager does not see specific symptoms that are characteristic of a trace mineral deficiency. Instead, the deer grows and/or reproduces at a reduced rate, uses feed less efficiently and operates with a depressed immune system; this is inefficient, lessens the profitability via lower carcass weights, trophy size and recruitment rates.


Calcium is not a trace element as such, but it is important to the well-being of all vertebrates; more of this later though.


Deficient Area Problem

There are several examples where an area of the country was not recognised as being trace mineral deficient in the past but now has been shown to require trace element supplementation. This generalisation is particularly true of the Scottish deer range. Much of those areas deficient in Selenium particularly have only recently been recognised, and only then by individuals taking a particular interest in the field of soil science on either a professional or lay basis. Another factor to consider is the moving of feedstuffs from one region to others. There is nothing to prevent feed grown in a trace mineral deficient area from being transported to another area where the feed grown is supposedly adequate in the particular mineral. Ask yourself: Do I actually know in what state my Forest is concerning trace element availability?


Salt as a Carrier of Trace Minerals

Salt is a natural carrier for trace minerals, since all animals have a natural appetite for salt. When deer are on open hill pasture/grazing, their requirements for trace elements can be satisfied with a distribution of mineralised blocks placed in situ, a much more practicable solution than either bringing up expensive concentrates or other feedstuffs into areas of limited or difficult access, or to coax the hinds down and away from their preferred hefts. In this way, the deer can consume salt and the trace minerals contained therein on their preferred ranges, which also helps prevent potching of ground by concentrated use of one or two areas for feeding.


KNZ WILD blocks are made using 100% pure, refined vacuum salt, as opposed to rock salt, which has been shown often to contain traces of Molybdenum, Cadmium and other heavy metal elements which prevent the uptake of those minerals that benefit the deer, i.e. Copper, Cobalt, Magnesium and Selenium. The pure vacuum salt is also more palatable to deer than rocksalt. The so-called "High Energy" protein blocks do nothing to better enable deer to utilise the readily available natural forage (it is almost never that one finds a deer with an empty stomach, though they can easily starve with a belly full of forage that they are unable to metabolise), but they do have the ability to break and excessively wear the deer’s teeth, further exacerbating their problems with conversion of the bulk of their (naturally occurring) food. Deer have shown themselves perfectly able to survive on an extensive, low protein high fibre diet, PROVIDING they have access to the trace elements in their required levels. Indeed, one could easily feed deer with chocolate, were the only criteria to put weight on to them, but this would do little to benefit the deer’s health when what is really required is trace element supplementation. The KNZ VILT product has been developed specifically to address the trace element requirements of deer in our increasingly acidic environment.


Value of Trace Minerals

Various recent studies have shown that adding trace minerals to animal diets benefits productivity even when no deficiency symptoms are obvious. One finding was the reduction in time from beginning of the breeding season to actual conception; this earlier conception date results in a heavier weaning weight of the calf, and this can make the vital difference between an animal going on to become heavier in later life, and pass on the improvement in subsequent generations. Indeed, studies at Trolle Ljungby Estate in Skåne, Southern Sweden, where most of the practical testing was initiated, showed carcass gains in yearling animals (200 culled annually) averaging over 10kg (22lb) in animals produced from dams having access to the mineral block as it is today. On 200 animals this represented 2 metric tonnes more venison!



All ruminants (including deer) are susceptible to magnesium deficiency in the blood, known variously as staggers, hypomagnesic, lactation or grass tetany. Losses occur every year in both domestic and wild ruminants, with up to 1% of cattle affected in the UK annually, of which roughly one third cases prove fatal. Magnesium is a mineral that is required by all animals and functions as an enzyme cofactor. It is vital to the central nervous system. Animals grazing lush, rapidly growing (often fertilised) grass are most susceptible. Prevention of staggers occurs when blood levels of magnesium absorption are maintained above 1.5 mg/100ml. Because the quantity of magnesium that can be mobilized from body stores decreases with age, sufficient magnesium must be consumed on a regular basis. Most magnesium compounds are unpalatable to ruminants when offered alone; they are generally included with salt is the most advantageous method of incorporation for several good reasons: i) their natural appetence for salt ensures increased intake of magnesium; ii) the intake of both salt and magnesium boosts magnesium absorption, and iii) grazing lush grasses and lactation usually increases a ruminant’s appetite for salt , which means that increased magnesium intake is likely to occur at the time of greatest need.




Copper is required for the activity of enzymes associated with iron metabolism, elastin and collagen formation, melanin production, and the integrity of the central nervous system. Copper has been shown to be the most important of the trace elements for the overall well-being of deer. A minimum requirement for copper cannot be given with great accuracy, since copper absorption and utilization in the animal can be markedly affected by several mineral elements and other dietary factors. For example, it is known that molybdenum can depress copper absorption in deer; molybdenum levels rise in areas of increased acidity, whether naturally occurring or where exacerbated by the influence of acidification of the land through acid rain, airborne pollution and even increased levels of acidity caused by the interaction of rainwater runoff in softwood plantations. The presence or absence of sulphur should also be considered when evaluating the amount of copper uptake. Another study (in Scotland) has demonstrated that enriching pasture by means of application of lime to the ground also has the effect of suppressing copper absorption, even in areas where only a relatively light dressing of lime has been made, and well before the area could remotely be described as being over-limed. Mineral levels in water also affect copper absorption, though this is generally of lesser importance where deer are considered.

About 25 ppm of copper is beneficial to deer, roughly double the normal requirement of sheep.



Manganese was first recognised as a necessary nutrient for animals in the early 1930’s. Because manganese is found in many different feeds a deficiency is less likely than with most other trace minerals. Bone, kidney, liver, pancreas and pituitary gland are the sites of highest manganese concentration, which is at relatively lower levels than other trace minerals. Notwithstanding, it is still a critical nutrient for several functions. Around 40 ppm are required by deer for best health.



Zinc is required for normal protein synthesis and metabolism, and it is also a component of insulin so that it functions in carbohydrate metabolism. It is essential to all livestock (and humans). Deer require a minimum of 60 ppm for optimum health, and can take considerably more (+8X) and store it within the body to no ill effect.



Iron has been recognised as an essential nutrient for over 100 years. The iron in haemoglobin is essential for the proper function of every organ and tissue of the body. Only around 5% of Iron consumed is absorbed, however, and then only if it is in the ferrous state (Fe ++). Iron is low in milk of ruminants, including deer, varying from .5 to 1 ppm; optimum levels for deer are around 70 ppm.



Cobalt is only known to be required for animal life as a constituent of Vitamin B12, which has 4% cobalt in its chemical structure. Essentially Cobalt deficiency equals Vitamin B12 deficiency. It was first shown to be of value to ruminants in 1935. prior to that time, ruminants could not be successfully produced in many areas of the world because of severe cobalt deficiencies. Animals transferred from these "sick areas" would respond when transferred to "healthy areas". A 0.19 or greater ppm count of Vit.B12 in liver tissue is indicative of cobalt sufficiency in ruminant animals, and deer can accommodate cobalt at levels above 25 ppm.



Around 1900, scientists first recognised that Iodine was required for the proper functioning of the thyroid gland, and that iodine deficiency caused goiter. Shortly thereafter, iodised salt became widely accepted as a means of preventing goiter in man and animals. Though only small amounts of iodine are required by both, levels of in excess of 50ppm can be safely accommodated by deer.



Selenium was recognised as a potentially toxic mineral many years before it was identified as an essential nutrient It was in 1957 that its role in prevention of liver necrosis was recognised. Selenium is present in all cells in the body at low levels. Toxic levels are normally between 5-10 ppm; 2.5ppm are safe levels for deer to accommodate.



Studies have indicated that Chromium supplementation lowers stress-related losses of other trace minerals; this is important in deer, and it is likely that this element will be the next trace element to routinely be added to mineral supplement feedblocks. Phosphorus and Calcium are both vital for bodily development, but this development cannot occur in the absence or deficiency of Copper, which is vital for bodily development; KNZ is currently formulating a suitably stable compound of Phosphorus for inclusion in their mineral blocks in the near future. Currently available block form products purporting to offer Calcium generally do not offer it in sufficiently large quantities to be of any real benefit to the deer; if it is recognised that Calcium is required, then it is best administered by the strategic deposition of (min) 50kg heaps throughout the affected range, allowing free uptake of same in particular by the hinds, who are ultimately responsible for the future herd quality. This is also why KNZ recommend their mineral blocks be distributed throughout the Forest, in order for hinds to gain unfettered access in their preferred ranges, which by definition generally comprise the better naturally occurring feeding areas in any event. If quality stags are to be produced, one must begin with quality hinds, for no matter how big the master stag, if he is serving mediocre quality hinds, the end result can only be a mediocre calf, it’s that simple.


Further information and trial results concerning trace element utilisation and related studies are available upon request from the Rowett Research Institute, tel: 01224 712 751. You could also fax Bo Lagergren, Chief Development Scientist: 0046 8643 4990. He’d be happy to explain the need for correct trace elements.


Finally, I would respectfully venture the question: what makes you think you are doing the best you can (both in terms of value for money for the Estate, i.e. what your return is per pound spent on your current product, and improving birth weights of calves, your next generation of deer) for your deer at present? You may also wish to consider that in the process of manufacture of both feed and mineral blocks vitamins are in fact released/destroyed by the pressure and heat involved; KNZ have studiously avoided spurious claims for the properties of their product, but we are only too happy to submit our blocks for clinical analysis; we know that what is written on the content label is EXACTLY what is contained in the block. It is a pity that other companies cannot give anything better than calculated values (in effect estimated analyses) as opposed to actual content descriptions on their products.


This is all very well, but misses the point somewhat. Names and phone numbers of deer managers from up and down the length of the country who are convinced of the benefits of the product can be supplied, but the only way you will find out if they "work" is to try them; you are free to accept or deny any of the above information, it is of little consequence to the deer what either of us think.


On a personal note, I am interested in seeing the better management of our deer resource, and for the continued well-being of Scottish rural and estates’ economy which are increasingly coming under pressure from other areas with alternative agendas, which ultimately and somewhat inevitably threaten to impact on the deer; the only way to combat this is to increase the status/value of the deer.

D Steve Wright

Mortlach Sporting



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