Minerals and Mineral Deficiencies

Major elements		Trace elements
	Calcium		Iron
	Phosphorus		Zinc
	Potassium		Copper
	Sodium		Molybdenum
	Chlorine		Selenium
	Sulphur		Iodine
	Magnesium		Manganese
			Cobalt

Functions

Phosphorus has more known functions in the animal body than any other element.

• Part of bone structure
• Component of some proteins, lipids and nucleic acids
• Energy metabolism

Deficiency symptoms

There are extensive areas of phosphorus-deficient soils in tropical and sub-tropical areas of the world, and phosphorus deficiency is the most widespread of all the mineral disorders affecting grazing livestock.

• Rickets (young animals), osteomalacia (older animals)
• Depraved appetite (animals will chew wood, bones, rags etc.)
• Stiff joints, muscular weakness
• Poor fertility
• Low growth rates

Sources

• Cereal grains
• Fish meal and bone products

The phosphorus in cereals (and other plants) is in the form of phytate. This is an organic compound which binds the phosphorus and makes it unavailable to pigs and poultry. In sheep and goats, the rumen micro-organisms break down the phytate and make the phosphorus available to the sheep or goat. Phosphorus in cereals is therefore used much more efficiently by sheep and goats than by pigs and poultry.

Function

• Maintains the right concentration of salts in the body fluids, and the acid balance of the body.
• Involved in nerve signals

Deficiency symptoms

Generally rare because the potassium content of plants is high. Areas where soil potassium concentrations are low ( Brazil, Panama and Uganda) may give rise to potassium deficiency in grazing animals especially at the end of the dry season.

• Low growth, weakness, paralysis and death.

Excess potassium is normally excreted from the body (usually in the urine). High intakes of potassium may inhibit magnesium absorption and cause magnesium deficiency.

Sources

Found in all plants.

Function

• Maintenance of salt concentration in body fluids
• Maintenance of acid-base balance.
• Transmission of nerve impulses
•  

Deficiency symptoms

This occurs in many parts of the world, but especially in tropical areas of Africa.

• Dehydration
• Poor growth
•  

Sources

• Common salt
• Plants are relatively poor sources of sodium.
  

Function

• Acid-base balance
• Maintenance of salt concentration

Deficiency symptoms

• Alkalosis (excessive bicarbonate in the blood)
• Growth retarded in extreme cases.

 Sources

• Common salt

Salt is important in the diet of livestock, but too much salt in the diet is harmful. Salt poisoning is quite common, especially when the supply of drinking water is limited. Diets containing high concentrations of salt (40 g/kg for hens, just 20 g/kg for chicks and pigs) will kill the animal if the supply of water is limited.

Function

Component of some amino acids, which are rich in certain proteins (e.g. keratin that forms hooves, horn and hair).

 Sources

• Proteins. Generally a deficiency of sulphur would arise from a deficiency of protein in the diet.
  

Function

• Component of the skeleton
• Essential for carbohydrate and fat metabolism

Deficiency symptoms

• Paralysis and death
• Convulsions

Sources

• Bran
• Oilseed meals and cakes
  

Function

• Component of haemoglobin (transports oxygen round the body)
• Major role in energy metabolism

Deficiency symptoms

The most widely recognized symptom is anaemia (observed as pale pink membranes round the eye). Piglets are particularly susceptible to anaemia and need access to soil to root around. Piglets suffering from anaemia also have poor appetite and growth, and ‘thumps’ (laboured and spasmodic breathing).

Sources

• Green, leafy materials
• Most legumes and seed coats

Iron toxicity is not common, as the animal usually reduces its absorption of iron when it is overloaded, and increases its absorption during times of iron need.

Zinc has been found in every tissue in the animal body. High concentrations are found in the skin, hair and wool; the highest concentration is found in semen. Zinc accumulates in the bone, unlike all the other trace elements that tend to accumulate in the liver.

Function

• Component of several enzymes
• Involved in cell replication
• Production, storage and secretion of hormones
• Involvement in the immune system
• Involved in maintaining salt balance.

Deficiency symptoms

Rarely seen; the requirements for zinc are not high and zinc is widely distributed in feeds.

• Pigs: below normal growth, low appetite, reddening of skin which then erupts and forms scabs (parakerotosis)
• Chicks: retarded growth, foot abnormalities, ‘frizzled’ feathers, parakeratosis, ‘swollen hock syndrome’.
• Calves: inflammation of the nose and mouth, stiffness of the joints, swollen feet, parakeratosis

Sources

• Bran and germ of cereal grains

Most animals are fairly tolerant of high doses of zinc, and zinc toxicity is rare. Large amounts of zinc in the diet reduce feed consumption and may induce copper deficiency.

Copper is stored in the liver. Acute copper poisoning is rare, but if small excesses are continually fed then eventually the accumulated copper reaches a toxic threshold. Susceptibility to copper poisoning varies between species. Pigs can tolerate large amounts of copper, and it is relatively unusual to cause copper toxicity in cows. However, sheep are extremely sensitive to copper poisoning. Copper poisoning causes jaundice and death from liver failure.

Functions

• Involved in haemoglobin formation.
• Involved in iron absorption from the gut, and in the use of iron in haemoglobin manufacture
• Needed for normal colouring of hair, fur and wool.
• Reduces susceptibility to infection in lambs.

Deficiency symptoms

• Anaemia, poor growth, bone disorders
• Diarrhoea, infertility
• Discolouring of hair and wool
• Gut disturbances and damage to the brain and spinal cord.
• ‘Swayback’ in lambs. If this occurs at birth it is irreversible and can only be prevented by supplying the ewe with sufficient copper. If signs do not show for several weeks after birth, then the effects can be prevented or postponed by supplementing the lamb with copper.
• Stringy or steely wool

Copper deficiency can also be caused (in sheep and goats) by grazing them on molybdenum-rich pastures. Too much molybdenum and/or sulphur reduces the availability of copper and cause copper deficiency. The copper, molybdenum and sulphur form an insoluble complex in the rumen, which renders the copper unavailable to the animal.

Sources

• Found in a wide range of feeds and the diet will usually contain sufficient copper.
  

Although molybdenum does have a function in the body (it forms part of a complex with some enzymes), requirements are extremely small. Molybdenum deficiency has not been observed under natural conditions with any species. Problems with molybdenum are much more likely to occur when it is in excess, as it reduces the availability of copper to ruminant animals. Scouring and weight loss are the main signs of molybdenum toxicity, although sheep and goats are less affected by this than large ruminants.

Selenium works with Vitamin E to protect the animal’s tissues from oxidation. Vitamin E keeps selenium in its active form, while selenium increases the absorption of Vitamin E from the gut and keeps it in the body’s circulation. As part of the process of oxidation, peroxides are formed (which damage the cells). Vitamin E prevents the production of peroxides and selenium destroys peroxides that are formed. Supplementing the diet with Vitamin E will therefore reduce the requirement for selenium (and vice versa). There are limits to this substitution, though. Vitamin E cannot completely replace selenium and selenium cannot completely replace Vitamin E.

Functions (with Vitamin E)

• Prevent oxidation damage to the cells of the body
• Involved in the functioning of the immune system
• Protection against heavy metal toxicity

Deficiency symptoms

• ‘Ill thrift’ in kids and lambs: weight loss and sometimes death
• Reduced hatchability and egg production in hens.

These deficiencies will probably only occur if the soil is deficient in selenium and livestock are only fed pasture grown on those soils. Extreme care should be taken if supplementing the diet with selenium, because it is extremely toxic and the margin between required dose and toxic amount is small.

 Selenium toxicity

Some areas have soils with very high selenium contents. Browse and pasture growing on this soil also has a high concentration of selenium, which can produce chronic disease called "alkali disease"or "blind staggers". Signs of this are:

• Dullness
• Stiff joints
• Loss of hair from tail
• Hoof deformities.

A concentration of 5 mg selenium/kg diet may be dangerous.

If the animal eats a single very high dose of selenium, it will suffer from acute poisoning, which causes sudden death from respiratory failure.

Iodine is found in small amounts throughout the body but its only known function is as a component of thyroxine. This is a hormone that is responsible for increasing the animal’s growth and metabolic rate.

Deficiency symptoms

• Goitre (swelling of the neck).
• Breeding animals give birth to hairless, weak or dead young.

Goitre may also be caused by toxins (goitrogens) in brassicas, soya, linseed and groundnuts. Some of these goitrogens inhibit the incorporation of iodine into thyroxine, and the symptoms cannot be alleviated by supplementing the diet with more iodine. The effect of the goitrogens in some plants, however, is overcome by ensuring adequate iodine is supplied.

Sources

The amount of iodine found in plants depends on the iodine status of the soil in which the plant was grown, and so there wide geographical variations in the iodine status of feeds (and livestock).

Iodine toxicity can occur even at relatively low concentrations of iodine in the diet (50 mg/kg or less for calves). Reduced hatchability and delayed hatching occurred in eggs laid by hens fed 312 mg iodine/kg diet. Pigs seem to be more tolerant to higher concentrations of iodine in the diet.

Manganese is involved in many reactions occurring in the body.

Deficiency symptoms

These have been observed in ruminants, pigs and poultry. Symptoms of acute deficiency are similar in all species and include:

• Retarded growth
• Skeletal abnormalities
• Reproductive failure
• Loss of co-ordination in the newborn.

Delayed oestrus and conception, also abortion in goats

• Perosis (slipped tendon) in chickens.
• Head retraction in chicks.

Sources

• Widely distributed in feeds.
• Higher in forages grown on acid soils.
• Most green feeds contain adequate amounts.

Poultry are quite tolerant of high concentrations of manganese in the diet, but pigs are more susceptible. They will show signs of manganese toxicity (depressed appetite and retarded growth) with concentrations of 0.5 g manganese/kg diet.

Cobalt is a component of Vitamin B 12 (cobalamin). Pigs and poultry need to be provided with this vitamin. The rumen micro-organisms make enough of this vitamin to meet the requirements for sheep and goats provided there is a sufficient supply of cobalt. This is usually the case, as most feeds contain some cobalt.

Excessive cobalt can be toxic, but there is a wide margin of safety between the nutritional requirement and the toxic amount. Unlike copper, cobalt is not retained in the body to any significant extent and so regular, small excesses of cobalt intake should not result in the animals later developing acute cobalt poisoning.