Certain mineral elements are required for the normal physiological functions of all the living creatures and such minerals are known as mineral nutrients. The mineral nutrients are classified into two groups on the basis of quantitative requirement in the body functions. Those elements which are required more than 90mg per kg body weight are called macro or major minerals, while those required less than 90mg per kg body weight are called micro or trace minerals. So far 25 minerals have been found involved in the functions of the body viz. growth, reproduction, maintenance and functioning of the body tissues. The 7 macro mineral nutrients are calcium, phosphorous, sodium, potassium, chlorine, magnesium and sulphur, and 18 trace elements are iron, iodine, copper, cobalt, manganese, zinc, molybdenum, selenium, chromium, fluorine, silicon, tin, lead, cadmium, vanadium, mercury, arsenic and nickel. The sources of minerals in livestock feeding are highly variable and depend on the system of feeding and regional traditions in India . The common sources of minerals for the farm animals are- minerals in feed stuff, drinking water, soil and mineral supplements.
The informations contained in Animal Health year book of FAO/WHO report, almost 80% are nutritional factors of which more than half are due to mineral imbalances that is deficiencies or excess. The disorders due to dietary mineral imbalances may be-deficiencies of minerals responsible for poor performance, reduced production, poor health and higher susceptibility to infections due to lowered vitality or excess of minerals may interfere with the availability of other nutrients causing secondary deficiency. Some of minerals are toxic and excess may be fatal also. So minerals in animal nutrition having too much importance for better growth and production. This paper provides the knowledge to farmers about some important aspects of macro minerals.
Calcium is the most abundant mineral in the body and 99% is found in the skeleton and a small fraction (1%) lies outside the skeleton is also important to survival. Ca comprises about 46% of the total body minerals. The main functions of Ca are formation of bone and milk, blood clotting, metabolic regulation (cell signalling), muscle contraction and transmission of muscle impulses. Reduced extra cellular blood calcium increases the irritability of nerve tissue and in severe cases it may lead to tetany and convulsions, where as excessive Ca depresses cardiac activity which may lead to respiratory and cardiac failure. Deficiency of Ca may be primary- due to lack of the element in the diet or, secondary- due to marginal Ca intake aggravated by a high phosphorous intake (altered Ca:P ratio), but in both cases it results in osteodystrophy. While primary deficiencies causes no specific syndromes, secondary deficiency produces rickets, osteomalacia and degenerative arthropathy. Non specific symptoms like inappetance, stiffness, tendancy of bones to fracture, disinclination to stand, difficult parturition, reduced milk yield, loss of condition and reduced fertility (Radostits et al., 2000). The higher susceptibility of older cows to Ca deficiency may be due to a reduction in 1,25 (OH) 2 D 3 receptors in intestine and bone (Horst et al., 1990). Hypocalcemia is most common in high yielding dairy cows, called as milk fever, which is a most important metabolic disease. This condition is associated with parturition and initiation of lactation. Older (5-10 years) dairy cows and Jersey are particularly more susceptible. With in 48 hours of calving, the cow become restless and shows muscular weakness, circulatory failue, muscular twitching, loss of milk yield, sternal and lateral recumbency. If affected animal does not treated immediately, death may ensue. Milk fever may be controlled by a single i/v infusion of 10-12g Ca as calcium borogluconate. Forages are generally satisfactory sources of Ca for grazing livestock. Inorganic Ca supplements are steamed bone meal, Ca carbonate, ground lime stone, mono calcium phosphate and dicalcium phosphate.
Phosphorous is one of the most essential minerals required by rumen microbes, as it is a constituent of primary cell metabolites i.e. nucleic acids, coenzymes like flavin phosphate, pyridoxal phosphate and thiamine phosphate and cell wall constituents like teichoic acid and phospholipids (Underwood et al., 1999). Phosphorous comprise about 29% of the total body minerals. Phosphorous deficiency is the most wide spread and economically important of all the mineral deficiencies affecting grazing livestock. Phosphorous deficiency in dairy animals occurs due to low dietary intake, improper absorption, interaction with minerals like Ca, Mo, S, Fe and Al. Hypophosphataemia in dairy animals has been reported from Punjab, J & K, Haryana, Karnataka, Assam, UP and Uttaranchal. Phosphorous deficient animals usually show pica, poor growth, stiffness of gait, anaemia, post parturient haemoglobinuria, infertility and in late stages osteodystrophy. Retarded growth, low milk yield and reduced fertility are the earliest signs of hypophosphataemia. Read et al. (1986a) reported that the sub normal fertility was manifested by depressed or irregular estrus which prevented or delayed conception in cattle, while sheep were not affected. It is claimed that relative infertility occurs in dairy heifers on daily intake of less than 40g of phosphate. The clinical signs occur when blood levels have fallen from the normal of 4-5mg per dl to 1.5-3.5mg per dl. The clinical signs of phosphorous deficiency included general unthriftiness, marked body weight loss, reduced feed consumption, reluctance to move, bone fractures and finely impaired reproduction. Blood level of phosphorous is not good indicator of the phosphorous status of an animal because it can remain at normal levels for long periods after cattle have been exposed to a serious deficiency of the treatment. Daily phosphorous requirement of dairy cattle is 1.9 – 3.9g/kg DM (NRC, 1984). The inorganic phosphorous supplements include deflourinated rock phosphate, monocalcium phosphate, dicalcium phosphate and sodium phosphate. For the prevention and control of P deficiency, supplementing P through water supply requires water soluble source of P like sodium phosphate or ammonium polyphosphate. Super phosphate is the cheapest source of water soluble phosphate. Treatment includes a single dose of 10% solution of sodium acid phosphate @ 11ml/100 kg body weight orally or i/v. A dietary Ca:P ratio between 1:1 and 2:1 is ideal for growth and bone formation.
Sodium (Na) and Chloride (Cl):
Sodium in animals is present largely as the sodium ion and its major functions concerns with the regulation of crystalloid osmotic pressure, acid-base balance, maintenance of membrane potentials, transmission of nerve impulses and the absorptive processes of monosaccharides, amino acids, pyrimidines and bile salts. The sodium is the chief cation of ECF. Sodium ions of ECF are balanced electrically by chloride ions and bicarbonate ions. The changes in osmotic pressure are largely dependent on the sodium concentration. During stress conditions the loss of sodium may be compensated to some extent by an increase in potassium but as this ability of animal is limited, any major loss of sodium leads to a significant lowering of osmotic pressure, loss of water and dehydration. A dietary deficiency of sodium is most likely to occur in milch animals because of the drainage through milk; in rapidly growing animals fed predominantly low-sodium, cereal based diets; under very hot environmental conditions. The Na and Cl deficiency symptoms in dairy animals include a marked polyuria, polydipsia, salt hunger, pica, drinking urin, loss of appetite and weight and a fall in milk production. A prolonged deficiency can cause decreased growth and unthrifty appearance culminating the shivering, incoordination, weakness and cardiac arrhythmia leading to death.
Diagnosis is usually by clinical findings in conjunction with urinary and salivary sodium levels- these being better indices of Na deficiency than serum levels, and anlysis of feed and water of Na and Cl. The oral administration of socium chloride is both preventive and rapidly curative. The salt supplementation @ 0.5% in the diet is considered to be fully adequate for all farm animals.
Potassium is the third most abundant element in the body. The main physiological functions of K include maintenance of acid-base balance, regulation of osmotic pressure, muscle contraction, transmission of nerve impulses and control of water balance. Potassium is the major cation of intracellular fluid and 89% of the total K is located within the cells. Dairy animals especially lactating having comparatively higher dietary requirement for K, because excessive loss of K through milk. Besides, stress, use of high concentrate diets, reduced feeding of K rich forages, and increase use of urea as nitrogen source also contribute to predispose the deficiency. Reduced appetite is one of the first sign of K deficiency. There is depressed growth, muscular weakness, stiffness and paralysis of limbs along with persistent diarrhoea when K is depleted from the body. The major symptoms are reduced feed and water intake, lower feed efficiency and a drop in milk yield. In severe cases near-complete inanition, pica tetany and death ensues. Low serum levels have some diagnostic value but lower dietary concentration in conjunction with reduced feed consumption seems to be best indicator of K status. For prevention and control of K deficiency, add K to the diet, may lead to improvement in milk and alleviation of stiffness and excessive irritability. When hypocalcaemia syndrome developed under the conditions like acidosis, stress and diarrhoea, the potassium chloride is given daily at dose rate of 42g/100kf body weight, i/v and orally for 5 days.
It is an essential element in the diet of higher animals. About 60-70% of the body Mg present in the skeleton and rest of it is present in the intracellular fluids and organelles. Mg acts as a catalyst in various enzymes and plays a vital role in the metabolism of carbohydrate, lipids, nucleic acids and proteins. Mg ions coordinate neuromuscular activity and effect autonomic control in the heart.
Mg deficiency is manifested clinically by retarded growth, hyperirritability and tetany, peripheral vasodilation, anorexia, muscular incoordination and convulsions. Lactation tetany, variously known as hypomagnesaemia tetany, grass tetany, grass staggers and wheat pasture poisoning affecting all classes of ruminants is characterised by hypomagnesaemia and usually hypocalcaemia and clinically ends up in muscular spasms and convulsions, and death due to respiratory failure. Diagnosis of Mg deficiency usually by assaing the total Ca and Mg levels in serum and cerebrospinal fluid: a reduction in Mg content of cerebrospinal fluid and serum are <1.6mg/dl and <1.23mg/dl respectively. The total serum Ca levels may reduce to 5-8mg/dl. The most important diagnostic feature of Mg deficiency is the presence of a scuffed arc of the field by the feet of the animal. An effective treatment for the condition includes use of combined calcium-magnesium preparations (eg. Mifex) i/v followed by a s/c injection. Symptoms of tetany appears within 10 min. following single dose of 200-300ml of a 20% solution of magnesium sulphate or magnesium lactate s/c. Along with this treatment, the cattle should be immediately removed from the tetany producing herbage and fed on ration treated with magnesium . Control measures viz. feeding of Mg salts as supplement, use of Mg bullets, top dressing of pasture with Mg-preparations, provision of appropriate sheltering in area of winter pasturing.
The animal body contain about 0.15% of S in the form of sulphates. Its concentration in the body increases with age, probably due to the intensified biosynthesis of muscle protein and the accumulation of S in hair and feathers. The protein keratin, which is found in hair (or feathers) and horney tissues is especially rich in S. Oil cakes are the richest source of S followed by greens, cereals and bran, poorest source are the cereal straws. Sirohi et al. (1996) reported average S content in cereals 0.07-0.23, oil cakes 1.64-2.5, green fodders 0.29-0.59, grasses 0.1-0.4, straws 0.016-0.03, bran 0.15-0.18 percent on dry basis. In recent years some agricultural practices, feeding and management practices have increased the need for S addition to dairy rations like increased feeding of corn silage, which often is very low in S, the extensive use of non protein nitrogen (to economise the feeding of animals), use of triple super phosphate fertilizer instead of ordinary sulphur phosphate, eliminates a source of available sulphur. Symptoms of S deficiency include retardation of growth, shedding of wool or hair, profuse salivation and lacrimation and finally, the emaciated animals dies. Requirement of S for dairy cattle is 0.13 to 0.2% of the ration. Requirement for dairy cattle are influenced by the N:S ratio. Accordingly N to S ratio of 10:1 has been recommended (NRC, 1978). Reduced serum sulphate, increased blood urea and accumulation of in the rumen are the diagnostic feature of S deficiency. Excessive S may overload the urinary excretion system and reduced feed intake, weight gain and milk production. Toxic levels of S is 0.5 to 1% of the ration in cattle. Acute toxicity symptoms include abdominal pain, muscle twitching, diarrhoea, and severe dehydration, strong odour of suffied on the breath, congested lungs and acute enteritis. Phosphorous fertilizers provide sufficient S to avoid the need for specific S source. Addition of calcium sulphate in molasses urea bran block is an ideal supplement for the stock grazing S and N deficient pastures. Recently emphasis is on feeding S in form of methionine analogues (eg. Malyl and methmalyi methonine) which are not degraded by rumen microbes. Methionine analogue increase milk fat in high yielding dairy cows.
Horst, R.L., Goff, J.P. and Reinhardt, T.A. (1990). Advancing age results in reduction of ntestinal and bone 1,25 dihydroxy vitamin D receptors. Endocrinology. 126: 1053- 057.
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Read, M.P., Engles, E.A.N. and Smith, W.A. (1986a). Phosphorous and the grazing uminant.1. The effect of supplementary phosphorous on sheep at Armoedsvlakte. South frican J. Anim. Sci. 16: 1-6.
Underwood, E.J. (1999). The mineral nutrition of livestock, 2 nd edn, Commonwealth gricultural Bureaux, Farham Royal , UK .
- Neelesh Sharma - Research Fellow
- Kafil Hussain - Assistant Professor