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Nutrients are elements in feed that are used by the animal for maintenance, growth, and production. Some are needed in large amounts while others are needed in small amounts.

In general, nutrients are divided into five categories: water, protein, energy (carbohydrates and fats), minerals and vitamins.


Water is the most essential nutrient and the nutrient to which livestock should always have access. A mature animal's body is about 75% water. Water comprises most of the blood. Blood carries nutrients to cells throughout the body and also transports waste products away. Water is necessary for certain chemical reactions to occur. Water acts as the body's cooling system and helps regulate body heat. Water also acts as a lubricant for the body's organs. Any living thing can live longer without food than without water.


Proteins are complex chemical substances from which the body tissues are built. Each protein is comprised of smaller units called amino acids. Each species of livestock has the ability within their body to produce some amino acids. These compounds are called non-essential amino acids. Other necessary amino acids cannot be manufactured by the animal's body and are called essential amino acids. Essential amino acids must be supplied through the feed. Proteins can be used as energy, too. When feed contains too much protein, the extra protein can be used as energy. Soybean meal and fish meal are high in protein. Corn and barley are lower in protein. Proteins are used by the animal to produce muscle, bone, blood, skin, fur, hair, wool, hooves, and horns. Examples of protein feeds include: cottonseed meal, soybean meal, linseed meal, corn gluten meal, distillers grains, brewers grain, and meat meal. Non-protein nitrogen sources such as urea can be used by ruminant animals to make protein.


Carbohydrates and fats are used as fuel to supply energy. The main use of energy is to allow chemical reactions to occur, resulting in conversion of feed to body tissues such as meat. Energy is constantly needed by the body. It is the "body fuel" which is used to maintain body temperature and to produce body movement. Energy nutrients that are not used are stored as fat until needed. Sugar, starch, and fiber are carbohydrates. Grains contain a lot of carbohydrates. Corn oil and tallow are fats. Fat furnishes at least two and one-half times more energy than an equal amount of carbohydrate.


Minerals are used to build bones and teeth and in chemical reactions necessary for many life processes. For example, calcium is needed for bone formation. Phosphorus is involved in bone growth and maintenance of good appetite and water consumption. Minerals required in very small amounts are called trace or micro minerals. These are generally supplied by using a mineral or mineral/vitamin pre-mix. Some examples include copper, zinc, and iron. Larger amounts of required minerals are macro minerals. These include calcium, phosphorus, sodium and chloride. These compounds may be included in a mineral pre-mix or purchased separately. Examples of mineral supplements are bone meal, defluorinated phosphate, dicalcium phosphate, salt, trace mineralized salt, oyster shells, and limestone.


Vitamins are compounds which help the body absorb and use other nutrients. Vitamins are essential for growth and are needed in small amounts by the animal. There are two types of vitamins: fat-soluble (A, D, E and K) and water soluble (B complex and C). Some animals can ;make their own vitamins within their bodies, other species cannot. Because of this fact, a steer should not be fed the same vitamin pre-mix as a pig. Vitamins are generally supplied in animal feed in the form of a supplement or provided by consumption of green pasture.