‘Mineral’ is the term used to describe elements needed in nutrition that are found in plant and animal-derived sources, but are also supplied as mined ores or chemicals.
Animals have evolved to extract minerals from the plant material they consume. Plants obtain minerals from the soil they grow in, and their ability to absorb and use these minerals is dictated by the amount of minerals (naturally or by fertiliser) it contains, pH (acidity) and biological activity (soil invertebrates and micro-organisms that modify inorganic forms into compounds that can be taken up by roots). Nowadays there are ‘organic’ chelated minerals available that mimic the natural compounds in plant and animal tissue that are better absorbed and stored and utilised in tissues. The following article looks at the macro minerals – those supplied in larger amounts (grams per day).
Minerals can interfere with each other in uptake in the gut, and so must be carefully balanced, especially when using inorganic forms. Macrominerals are those required and used in larger amounts, and include calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), sodium (Na), chlorine (Cl) and sulphur (S). Na and Cl combine to form common table salt. Calcium is an important component of bones, teeth and enzymes and is needed for muscle contraction, cell structures and blood clotting. It is commonly supplied via limestone grit or flour, as a sulphate or protein chelate (organic) or from algae and is present in grain and forage. Vitamin D is needed for its absorption, and even if Ca is supplied in the correct amount, deficiencies will result in poor skeletal development. Ca is less available from forage grown in acidic soils, resulting in poorer intake, and certain forages, such as kikuyu grass, contain high levels of oxalates reduce Ca intake by binding it up so it cannot be absorbed from the gut.
Phosphorus is essential for bone development and growth and is the main component of the energy (ATP) released in the body. Again, it is tied closely to Ca, and oxalates affect its availability. Forms include dicalcium phosphorus (known as ‘dical’ by nutritionists). Correct levels of salt intake are important to ensure P absorption. Excess intake can create skeletal abnormalities, and the ratio between P and Ca is very important. High P, low Ca diets (e.g., high bran and oat feeds) are linked to hyperparathyroidism.
Magnesium is needed in enzyme formation, bone, blood and muscle contraction. It is found in high levels in colostrum, and is available as both oxide and sulphate forms plus a host of other types, including as a citrate and aspartate. Excess P intake is known to reduce Mg absorption. Its SO4 form acts as an anaesthetic when injected intravenously, and can have a relaxing effect when fed to cattle. Deficiency symptoms include tremors, nervous behaviour, tetanus-like symptoms and collapse.
Potassium is important in muscle contraction and nerve function. It is found in blood and skin and is an important electrolyte, maintaining water balance in cells. It is found in forage and oilseeds, or in an inorganic sulphate form. Deficiency signs include feed refusal and dehydration. Excessive levels induce heart attacks.
Sodium is most commonly consumed as NaCl salt. It is important in the central nervous system, as an electrolyte and in the transport of nutrients into cells. Farmers can supply Na as a salt lick – but intake in this form is not well controlled and can vary between none and 31 g/day. It is stored on bone reserves, and deficiencies are manifested as licking anything sweaty, poor appetite, uncoordination and muscle dysfunction – so often related to tying up (muscle stiffness) and dehydration. Chlorine is supplied in its chloride state bound to Na. It is needed for the same functions and has the same deficiency symptoms as Na, and their uptake is closely linked. As a result, overfeeding Na (e.g., sodium bicarbonate supplementation) can cause Cl deficiency. Low Cl can reduce milk production. Grazing animals are generally salt tolerant as long as they have free access to good quality water, which can be a problem in Australia. Salt toxicity is manifested as disorders of the nervous system.
Sulphur is a key component in the essential amino acids methionine and cysteine, is needed to produce vitamin B12, blood proteins, insulin (for carbohydrate use) and chondroitin sulphate within joints. It is found in abundance in plant protein sources. Excessive intake causes lethargy, colic, ‘heaves’ (laboured breathing), convulsions and jaundice (yellow membranes) in mammals.
Talk to your local Reid’s dairy specialist today about the benefits of our mash and the products we can offer to suit your requirements on 1300 REID FEED or enquire here >
Author
Dr Lucy Waldron
PhD RNutr AAS RFellow (Massey)
