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Agriculture for Secondary Schools

elements are those minerals required in fairly large quantities. These include
calcium, phosphorus, sodium, chlorine, potassium, magnesium and sulphur. On the
other hand, micro-elements are those minerals required only in very small amounts.
These minerals are also termed as trace elements. These include iron, zinc, copper,
manganese, iodine, cobalt, molybdenum and selenium. Even though micro-elements
are essential, they are not likely to be limiting factors under most conditions.

Water
Water is a vital nutrient in the animal body. It makes up more than 60% of the total
animal body weight. It is important for maintenance of animal health and production
as it is the medium in which many body processes take place. It is also a major
component of most livestock products such as milk and eggs. The source of water
in the animal body is directly from drinking water and indirectly from feeds rich in
water. Some of the body processes also produce water mainly as the end product.

The functions of feed nutrients in animal body and sources of the nutrients are
summarised in Table 5.1.

Table 5.1: Functions of feed nutrients in animal body and their dietary sources
Nutrient Function(s) Sources
Carbohydrate • Provide animals with energy • Forages
for their daily requirements of • Cereals and cereal
metabolic activities by-products such as
• Excess carbohydrates are converted brans and molasses
to fats/oils and stored as energy • Starchy tubers
reserves within the animal body

Proteins • Build animal body tissues as • Leguminous fresh
they are component of muscles, and preserved
enzymes, connective tissues and forages
blood • Oil seed cakes
• They are component of milk, eggs, • Meat meal
and meat
• Repair and replace worn out body • Fish meal
tissues • Blood meal
• Play role in maintaining the health • Milk meal and milk
of the animal through synthesis of processing by-
antibodies products such as
• Play important role in synthesis of whey
hormones and certain enzymes
• They can be metabolised to give
out energy

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