Macro-minerals

Animals require more of the macro-minerals (Calcium, Phosphorus, Magnesium, Sodium, Potassium, Chlorine, Sulphur) than the micro-minerals (Iodine, Iron, Cobalt, Copper, Manganese, Molybdenum, Zinc, Selenium). If animals do not consume enough of the macro-minerals, this will cause reduced production, infertility problems, weakness of the bone and increased incidences of non-infectious diseases. In cows insufficient Calcium supply causes milk fever. Deficiencies in micro-minerals (trace elements) can cause a variety of diseases and conditions depending on which mineral is deficient.

Cattle grazing in areas around Nakuru usually have Cobalt deficiency and may develop a wasting disease called Nakuritis. They become anemic and eventually die. The forages are deficient of mineral Cobalt because the soils naturally contain very low levels of this micro-nutrient. Special mineral supplements are available for cattle in such areas. Too much of the micro-minerals can cause poisoning.

Calcium and Phosphorus are of particular importance when formulating rations. Legumes tend to have more Calcium and Phosphorus than grasses. Grains are low in Calcium. Young dark green forage tends to have more minerals than old, dry and yellow forages. Most tropical forages are low in Phosphorus.

Extra Calcium and Phosphorus usually need to be provided in the ration over and above that naturally present in the feed and mineral mix, especially for high yielding animals. Tables 2 and 3 show examples of sources of mineral salts (Forages and fodders, agricultural by-products, concentrates and minerals).

• Salt: (Sodium chloride) deficiency develops slow (weeks) but causes unthrifty appearance and low performance. Provision of ad lib salt licks are recommended. Plants tend to be low in both sodium and chlorine. It is therefore an important practice to give common salt to herbivores such as dairy cattle in order to prevent deficiency symptoms. Feeding diets deficient in salt may not show immediate symptoms, but chronic deficiency dairy cattle diets has been shown to lead to low appetite, low milk production and loss of weight. The addition of salt in the diet usually provide immediate cure. Fish meal, Guinea grass, Rhodes grass, Sweet potato vines, Rice and Oat straw and Sugarcane molasses are good sources for sodium.
  
• Calcium: Calcium is the most abundant mineral in the animal body. It is the most important constituent of the skeleton (bones) and teeth. Calcium also plays important roles in the activities of enzymes and hormones, which catalyse and/or balance the body metabolic processes. Agricultural lime, fish meal, milk, crushed shells, marble dust, some seaweed and green leafy forages, especially legumes, are good sources of calcium. Calcium tend to be low in old, dry and yellowing forages.
  
  In older (multiparous) dairy cows, a condition known as 'milk fever' (parturient paresis) commonly occurs shortly after calving caused by lack of available calcium. It is characterized by a lowering of the blood calcium level (hypocalcaemia), muscular spasms, and in extreme cases paralysis and unconsciousness.
  
  Deficiency symptoms: a) rickets in young stock. Joints become enlarged. Bones become soft and deformed. Condition may be corrected in early stages with calcium feeding. b) Osteomalacia or osteoporosis in older animals. Bones become porous and weak. Condition may be corrected by feeding calcium if bones do not break.Examples are known of cows fed too little calcium breaking their backs during mating
  
• Phosphorus: is needed for bone and teeth formation, building body tissue (growth of animals), milk and egg production. Signs of phosphorous deficiency include animals eating soil, chewing on non feed objects, slow or poor appetite, slow gain of bodyweight, low milk or egg production.Low dietary intakes of phosphorus have also been associated with poor fertility, apparent dysfunction of the ovaries causing inhibition, depression or irregular oestrus.
  Sources of Phosphorous: Bone meal, Rock phosphate, Superphosphates such as TSP etc. Also many improved salt licks contain phosphorus. African locust bean, pod pulp, Cotton seed meal, Wheat, bran, Rice bran and Sunflower cake are a good source of Phosphorous, but hays and straws have very low phosphorous content.
  
• Magnesium: is needed in proper functioning of the nervous system, carbohydrate metabolism and enzyme systems.
  Deficiencies: a) Hypermagnesaemia also called grass tetany, grass staggers and wheat poisoning can occur when animals are grazing on young fresh grass or wheat with high protein and potassium content and with very little content of magnesium.
  Symptoms are hyper excitability, paralyse and frequent death. More common in Europe than in Africa. Prevention: use animal salts containing magnesium especially when animals are grazing on new young grass or grains such as oats. Banana, stalks, Cassava, foliage, Pawpaw, leaves, Sweet potato vines, Cotton seed meal, soybean and Cocoa pods are good courses of magnesium. In Kenya magnesium deficiency hardly occurs, probably because of the available feeds.
  
• Sulphur: Sulphur requirements of cattle and sheep are around 0.1-0.2% of ration dry matter. For non-ruminants sulphur should be in the form of sulfur-containing proteins. A deficiency of sulphur will express itself as a protein deficiency, general unthriftiness and poor performance. Good sources of sulphur are Lucerne, Wheat- and Rice bran and Sunflower cake.