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CONTRIBUTOR(S): Vetstream Ltd, Eoin Ryan,

Minerals – the basics

Minerals – the basics

There are a host of minerals that cattle require to stay healthy. The requirement for minerals varies with life stages, disease status and geographical location. Your veterinarian and nutritionist can discuss minerals in more detail with you, but the key ones that may be mentioned are described below.

Macrominerals are those that are required in larger amounts (grams per day) and microminerals are required in smaller amounts (milligrams per day).


©Mo Kemp

What macrominerals are important?

Calcium and phosphorus

Calcium and phosphorous are listed together as their metabolism is so closely entwined.

Calcium is needed for bone growth and mineralization, nerve conduction, muscle contraction, milk production and enzyme activation. 99% of calcium is stored in the bones; this means that when calcium demands are increased (such as at calving) the calcium available in the blood stream may be quickly used up and the cow may be unable to release further calcium from the bones fast enough to meet demand. In this situation, the cow may become hypocalcemic and present with “milk fever”. Cows with milk fever are unable to stand as their muscles need calcium to work and become bloated, as the rumen also needs calcium to contract. These animals require emergency calcium supplementation, often directly into a vein.

Phosphorous is involved in all metabolic processes in the body; in particular, it is needed to create healthy DNA, is involved in bone growth, acid-base balance, normal estrus cycle, milk production and rumen microbe activity. 80% of phosphorous is found in the skeleton and teeth. Calcium and phosphorous are intrinsically linked and the signs of deficiency are similar to calcium deficiency, while also including signs of unusual eating habits (pica), such as licking salty surfaces, drinking urine/licking sweat, licking gate posts etc and occasionally can also present as blood-stained urine after calving. Hypophosphatemia (low phosphorus levels in the blood) do not always require intravenous supplementation but can often be corrected with adequate feeding of phosphorous rich feed. In addition to inadequate dietary supply, other conditions can also affect phosphate levels, such as feeding brassica species or concurrent copper deficiency, but these scenarios are less common.

Calcium and phosphorous are both considered relatively non-toxic and so are low risk for over-dosing cattle. However, extreme overdose can result in hard calcium deposits in tissues, which will adversely affect carcase quality. High phosphorous levels in growing male animals can result in the development of bladder stones, which can result in a life-threatening inability to urinate. Supplementation beyond adequate status will not yield any benefits, may cause additional problems and will increase costs.

Your veterinarian can assess calcium and phosphorus levels via blood samples. Calcium and phosphorus metabolism is complex and is affected by many different factors. Your veterinarian and nutritionist can assess your individual farm data as a whole and then advise as to appropriate management changes, dietary adjustments or supplementation if required.

Magnesium

Magnesium is an essential element and is involved in nearly all metabolic pathways in the body. It is essential for nerve conduction, muscle function and bone metabolism. The cow requires a constant supply of magnesium in the diet. Acute deficiency (hypomagnesemia/staggers) is thankfully uncommon, but the seizures can be alarming to witness and can be rapidly life threatening if not treated immediately by a veterinary surgeon. Chronic deficiency is often more subtle and may go unrecognized but results in reduced yields, loss of body condition and increased milk fever cases on farm. Many factors can affect the magnesium that is available to cattle, including magnesium levels in grass and feed, volume eaten by the cow, potassium and sodium levels in feed, rumen pH, ammonia levels in feed, other constituents of feed and genetics may also play a role.

Toxicity issues are seen if magnesium is over supplemented. Signs of over supplementation may include diarrhea, reduced feed intake and reduced performance. Signs may even progress to neurological signs and death, depending on the amount of magnesium consumed.

Your veterinarian can assess magnesium levels via blood samples (or from samples from the eye in deceased animals). Magnesium homeostasis is complex and is affected by many different factors. Your veterinarian and nutritionist can assess your individual farm data as a whole and then advise as to appropriate management changes, dietary adjustments or supplementation if required.

Sodium

Sodium and potassium are intrinsically linked in terms of their metabolism and function. Sodium is also usually considered in relation to chloride, due to the related metabolisms of these two elements.

These major minerals play a critical role in maintaining blood pressure, cellular function, acid-base balance (especially in the rumen via salivary sodium bicarbonate) and water metabolism.

Signs of sodium deficiency may include reduced production, behavioral changes (licking salty surfaces, drinking urine/licking sweat, licking gate posts etc), drinking and urinating more than usual, collapse and even death. Sodium deficiency can occur secondarily to magnesium deficiency. Sodium levels can be misleading on blood tests, so your veterinarian may also wish to test urine and fecal sodium levels.

Sodium is easy and inexpensive to supplement but excess sodium can lead to toxicity, so work with your veterinarian and nutritionist to ensure optimal levels are maintained.

Potassium

Sodium and potassium are intrinsically linked in terms of their metabolism and function. These major minerals play a critical role in maintaining blood pressure, cellular function, acid-base balance (especially in the rumen via salivary sodium bicarbonate) and water metabolism.

Potassium levels are generally high in grazed grass and conserved forages, due to the use of slurry and potash fertilizers as part of grassland management. Dietary potassium deficiency is therefore rare. High potassium concentrations in conserved forages leads to high dietary cation-anion balance and an increase risk of hypocalcemia if fed to dry cows. Cereal grains are low in potassium, although most concentrate feedstuffs will readily supply sufficient potassium for the cow’s requirements. Clinical signs of potassium deficiency are generally non-specific and include inappetence, poor growth rate and reduced milk production. Pica (eating abnormal substances, such as soil) may be observed. Low potassium also occurs in inappetent or downer cows and is often a secondary complication. Your veterinarian can assess potassium levels via blood test.

What microminerals are important?

Selenium

Selenium is an essential nutrient. It is utilized by the body for thyroid function and antioxidant activity. A deficiency in selenium may present as white muscle disease, ill thrift, poor growth rates, impaired immune function and/or poor reproductive performance. Selenium has a close relationship with vitamin E, and both vitamin E and selenium are often measured and dealt with concurrently by veterinarians and nutritionists. Selenium deficiency is one of the more common mineral deficiencies in the UK and may be diagnosed via blood tests or liver biopsy.

Selenium is one of the more toxic elements and overdose can have serious side effects, so it is important to work closely with your veterinarian and nutritionist. Signs of selenium overdose may include dullness, lack of vitality, poor coat, hair loss, sore/sloughing hooves, stiffness, lameness and even sudden death.

Cobalt

Cobalt is an essential trace mineral for ruminants, so although cattle don’t need very much at all, they do need tiny amounts. Cobalt is used by the rumen microbes to synthesize vitamin B12 (cobalamin) and propionate (used by the animal for growth). Deficiency of cobalt can lead to ill thrift, inappetence, “pine” and “wasting disease”. Cobalt deficiency is not uncommon in the UK and may be diagnosed by your veterinary surgeon. Your veterinarian may need to take blood samples or liver biopsies to investigate. If cobalt supplementation is required, then your veterinarian and nutritionist can advise as to the best form and method. Not all types of cobalt can be absorbed by the rumen, so it’s important to ensure you purchase the correct product and administer it effectively.

Cobalt is a very safe supplement, and it is very unlikely that you will over-dose cattle with it. However, supplementation beyond adequate status will not yield any benefits and will only increase costs, so work with your veterinarian and nutritionist to supplement in the most cost-effective way.

Copper

Copper is an essential element required for many metabolic processes, fertility, growth and, in particular, for its role in carrying oxygen in the blood stream. Other elements can influence the availability of copper to the cow, these include molybdenum, iron and sulphur which can bind up available copper in the rumen leading to thiomolybdate formation. The resultant absorption of this thiomolybdate molecule, together with less available copper and reduced activity of copper-containing enzymes in the body, is termed thiomolybdate toxicity. Therefore, although the true physiological copper requirements of the cow are very low, the presence of other elements may reduce the availability of copper with the cow and necessitate supplementation with higher levels.

Signs of copper deficiency may include rough, discolored coats, spectacle appearance around the eyes, hair loss around the muzzle and ears, scour, ill thrift, reduced fertility. Copper may be over-supplemented, and care should be taken not to exceed legal permissible levels for animals entering the human food chain. Excessive copper may result in signs of toxicity such as weak animals, listlessness, anorexia.

Your veterinarian can assess copper levels via blood samples and liver biopsy in conjunction with feed assessment.

Zinc

Zinc is required for the proper function of a wide variety of enzymes with roles in gene expression (DNA and RNA metabolism), appetite, vitamin A metabolism, immune system function and healthy hair and horn. Pastures in the UK usually contain adequate levels of zinc. Zinc levels in feedstuffs are closely correlated to zinc levels in the soil and plant maturity. Hay and straw tend to have low levels of zinc. Body zinc stores are limited, and so deficiency occurs rapidly when zinc supply from the diet cannot match requirements.

Signs of zinc deficiency are most often seen in 1-3 month old calves due to their higher growth requirements. Clinical signs include skin abnormalities such as baldness and thickening and cracking of the skin, especially of the lower limbs, muzzle and perineum. Loss of appetite and associated poor growth rates may also be observed and skeletal abnormalities such as bowing of limbs, stiff and swollen joints. Sperm quality may be adversely affected in bulls.

Your veterinarian can assess zinc status via blood test. Your veterinarian and nutritionist can advise you as to whether zinc supplementation is required and can ensure that you abide by legal regulations in regard to zinc supplementation. Over supplementation is possible and may result in reduced weight gain.

Iodine

Iodine is an essential element that is required by the thyroid gland, in its role regulating body metabolism (metabolic rate, temperature regulation and much more). Iodine deficiency can occur sporadically and may be a primary deficiency, due to low iodine content in the soil; or secondary deficiency, due to dietary goitrogens. Goitrogens are substances that act to disrupt iodine metabolism. These compounds are found in brassicas, legumes (white clover, kale, swedes) and other compounds. Selenium-containing enzymes are required for the conversion of iodine containing thyroid hormones, and so selenium deficiency may lead to secondary iodine deficiency.

Signs of deficiency include swollen thyroid glands (goitre), which is more obvious in new-born animals, stillbirths or birth of weak calves, and general ill thrift. Your veterinarian can assess iodine levels via blood test or post-mortem examination on abattoir carcasses. Your veterinarian and nutritionist can advise you on whether action is required. Supplementing iodine should be done with help from your veterinarian to ensure that you adhere to legal guidelines. Iodine is a cumulative, chronic poison. Humans are particularly sensitive to iodine toxicity, and there are restrictions on the iodine content of animal feeds to prevent excess iodine in meat and milk. Signs of iodine toxicity in cattle are similar to signs of iodine deficiency – goitre, reduced appetite, reduced milk production and abortions.

Manganese

Manganese is required for the function of a variety of enzymes involved in cartilage and bone development, metabolism, nervous system and antioxidant roles. Dietary content varies widely due to plant species and processing. Increased soil pH, for example liming, will reduce manganese uptake by plants.

Deficiencies will only occur on grazing deficient pastures (or maize silage-based rations). Requirements are likely to be greatest in animals which are both growing and pregnant, ie in-calf heifers. Signs of deficiency are mainly seen in neonatal animals, and include skeletal abnormalities, dwarfism, shortened limbs, swollen joints and neurological disorders. Your veterinarian can assess manganese levels via blood test or liver biopsy. Your veterinarian and nutritionist can advise as to whether action is required. Over supplementation may result in depressed appetites and poor growth rates.

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