The animal requires energy and proteins for different functions in the body system. Energy is required for maintenance (respiration and digestion), production (growth and work) and reproduction (pregnancy). An animal derives energy from dietary carbohydrates. Proteins are complex molecules which contain nitrogen and are required for formation of body tissues. Adequate supply of both energy and protein is essential for the general health of any animal. The requirement of both energy and protein by any animal depends on degree of production expected from the animal. Therefore prolonged deficits of both proteins and energy to an animal would result in loss of condition and in ability to be productive.

Malnutrition if prolonged eventually leads to death. Malnutrition caused by lack of energy and proteins may occur any where in the world but are more serious in the tropics. Animal feeds vary in their levels of energy and proteins. Straws such rice straw, wheat straw are poor source of both proteins and energy whereas concentrates like dairy meal may be rich in both.

In the tropics, good quality pastures may provide adequate protein and energy for maintenance and production. However in situations of drought, or overgrazing, animals are liable to receive inadequate energy or proteins from pastures.

Minerals are essential elements of animals' diets and they perform three functions in the animal body system. Minerals are important in the formation of body tissues, e.g. calcium and phosphorous. The other function of minerals is that they act as electrolytes to ensure that there is correct osmotic pressure and acid base balance in body fluids and tissues e.g. sodium, potassium and calcium. Lastly minerals have a function of catalyzing metabolic processes i.e. enzyme and hormone systems of the body e.g. iron, copper, and zinc.

Minerals are broadly classified into two categories: Macro-minerals and trace elements. Macro elements are required in large quantities in the animal's diet. These groups of minerals perform the formation of body tissues and act as electrolytes that correct the osmotic pressure in body fluids. Trace elements are required in small quantities in the diet of animals and perform the function of catalyzing metabolic processes in the body system.

Deficiencies or imbalances of these in the diet are controlled by physiological process in which the absorption in the gut and excretion in feces or urine of a particular mineral is regulated. In times of need, some minerals can be mobilized from the body reserves. Prolonged deficiencies may result in ill health the severity of which may depend on such factors as age of the animal, the level of their productivity and the quality of their diets.

Mineral deficiency or imbalance can occur in pastures and forage crops grown on soils that are deficient of a specific minerals. Therefore it is important to not that levels of minerals in a specific forage is determined by the soils in which they grow.

Most pastures in the tropics have adequate levels of calcium and some forages such as Lucerne are known to contain very high levels of calcium and this may complicate a concurrent deficiency of phosphorous.

Phosphorous deficiency is a major problem of grazing animals in the tropics and cattle are more at risk than small ruminants.

Most pastures in tropical Africa are known to be deficient in sodium.

Copper deficiency occurs in grazing animals in many parts of the world. Its occurrence is in two forms i.e. either as in a simple form in the diet or as a secondary deficiency due to other dietary elements which reduce its absorption in the gut. Such elements include high dietary molybdenum which occurs on alkaline soils or sulphur.

Selenium deficiency is most common in North America, Europe, Australia and New Zealand but less common in the tropics. The deficiency affects all species of domestic animals.

This deficiency affects grazing ruminants in many parts of the world. In Kenya severe deficiency of cobalt has been known to cause Nakuruitis.

This deficiency affects people and animals alike. Iodine deficient soils are known to occur in Sub Saharan Africa and South East Asia.

Signs of the above minerals are generally in two forms:

These are the most abundant minerals in the animal's body and they are mainly found in the bones and teeth. If the dietary supplies are limiting, the two minerals are mobilized from the bones to the blood through a complex metabolic pathway and likewise if the diet contains excessive levels of either of the two, then the rate of absorption of both from the gut to the blood stream is reduced.

Sodium is found largely in body fluids and bones. In farm animals, the deficiency is most serious in lactating animals and those animals that are over worked especially in high temperatures and therefore lose fluids and sodium through excessive sweating

The main functions of copper are formation of blood, provision of tissue collagen and wool and hair pigmentation. The deficiency can occur to any animal but is more common in ruminants. Copper is stored in the liver and is drawn when the levels in the diet are low. When liver and blood level become low, the signs would appear.

Selenium is essential for enzyme reactions which helps to protect cell membranes and is essential for growth and fertility. A selenium and vitamin E deficiency are interlinked and is the cause of the following diseases:

Retained placenta
White muscle disease and condition known to affect fast growing calves and lambs born from mothers that have been fed for a long time on deficient diets. Affected animals with white muscle disease are unable to stand or walk with unsteady gait.

Cobalt is required by ruminants for synthesis of vitamin B12 in the rumen for storage in the liver and kidney. During deficiency, cobalt is drawn from the liver and kidney. However prolonged deficiency of vitamin B12 would lead to:

Iodine is required for the hormones of the thyroid glands which control the rate of oxidation of cells and deficiency causes dysfunction of the thyroid gland.

Where mineral deficiency is suspected, it is advisable to consult a veterinarian to collect samples from selected animals for laboratory tests. The samples include blood and more specifically liver sample incase of copper and cobalt deficiencies.

In ruminant diseases, only fat soluble vitamins A,D and E have a real importance.

This is available in most green plants and if the animals graze on well managed pastures and forage, deficiencies will not occur. However, cattle fed on poor quality roughage such as poor quality hay, and straw would require supplementation.

This can be one by investigating the history of animals and their diets, analysis of blood and liver samples in a laboratory

This is little vitamin D in plants and animals obtain most of it by synthesizing the vitamin in the skin by action of ultra-violet rays from the sun. It is involved in the absorption of calcium and phosphorous from the intestines and the deposition of the minerals in bone together with maintenance of normal blood levels. Vitamin D deficiency in young calves is likely to occur when they are housed in houses with dim lights and offered poor quality diets.

Is done by injecting vitamin D and by correcting the ration, which may include oral supplementation with vitamin D

This is synthesized by the ruminal microorganisms and is available in leafy forages in plenty. Primary deficiency does not occur though can be induced by the action of dicoumarol poisoning such as warfarin rat poison and mouldy clover hay which inhibit the action of vitamin K. Vitamin K is involved in blood-clotting mechanisms.

This group of vitamins is synthesized by micro-organisms in the rumen and any excess is absorbed by the cow. They are also present in ample quantities in milk and therefore primary dietary deficiency is never seen.

This is produced in tissues of all farm livestock and dietary supply is un-necessary.