Poultry diets are composed primarily of a mixture of several feedstuffs such as cereal grains, soybean meal, animal byproduct meals, fats and vitamin and mineral premixes. These feedstuffs, together with water, provide the energy and nutrients that are essential for the bird's growth, production and health, namely proteins and amino acids, carbohydrates, fats, minerals and vitamins. The energy necessary for maintaining the bird's general metabolism and for producing meat and eggs is provided by the energy-yielding dietary components, primarily carbohydrates, fats and protein. Water
Water must be regarded as an essential nutrient, although it is not possible to state precise requirements. An animal can live without food longer than it can live without water. In a laying flock, a shortage of water for just a few hours can result in reduced egg production, so clean water should be available at all times. A laying hen drinks about 25% of her daily water intake during the last two hours of daylight.
Water plays an important role in the body of an animal. Water softens feed and carries it through the digestive tract. As a component of blood (90% of blood content), water carries nutrients from the digestive tract to cells and carries away waste products. Water also helps cool the bird through evaporation. (Birds do not have sweat glands, so their heat loss occurs in the air sacs and lungs through rapid respiration.)
A baby chick is composed of about 80% water. Even though this percentage decreases as a bird gets older, the need for water remains. The amount of water needed depends on various factors such as environmental temperature and relative humidity, the composition of the diet, rate of growth or egg production, and efficiency of kidney resorption of water in individual birds. As a general rule of thumb, birds drink approximately twice as much water as the amount of feed consumed on a weight basis, but water intake actually varies greatly.
Carbohydrates
Carbohydrates are a source of energy for poultry and makes up the largest portion of a poultry diet. Carbohydrates are typically eaten in the form of starch, sugar, cellulose, and other nonstarch compounds. Poultry typically do not digest cellulose and the nonstarch compounds, referred to as crude fiber, well. However, poultry are able to use most starches and sugars well. Important sources of carbohydrates in poultry diets include corn, wheat, barley, and other grains.
Fats
Fats have approximately two times the energy compared to carbohydrates by weight. Fats provide around 9 calories of energy per gram while carbohydrates provide around 4 calories of energy per gram. Fats are usually added to the feed for meat-type poultry to increase overall energy concentration, and in turn, improve productivity and feed efficiency. Examples of sources of fat include grease from restaurants, the rendering of animal carcasses and the refuse from vegetable oil refining.
The most important fatty acid to look out for in a poultry diet is linoleic acid. It is considered an essential fatty acid because poultry cannot generate it from other nutrients. Fat is also important in poultry diet for poultry to absorb fat soluble vitamins A, D, E and K. Fats also reduce grain dust and improves palatability of feed.
Proteins
Dietary requirements for protein are actually requirements for the amino acids contained in the dietary protein. Amino acids obtained from dietary protein are used by poultry to fulfil a diversity of functions. For example, amino acids, as proteins are primary constituents of structural and protective tissues, such as skin, feathers, bone matrix and ligaments. Because body proteins are in a dynamic state, with synthesis and degrading occurring continuously, an adequate intake of dietary amino acids is required. If dietary protein (amino acids) is inadequate, there is a reduction or cessation of growth or productivity and a withdrawal of protein from less vital body tissues to maintain the functions of more vital tissues.
Amino acids are typically divided into two categories: essential and nonessential. Essential amino acids are those that cannot be made in adequate amounts to meet the needs of the animal. The nonessential amino acids are those that the body can generate in sufficient quantities as long as appropriate starting material is available. There are 22 amino acids commonly found in feed ingredients. Of these, 11 are essential and must be supplied in the feed. Poultry diets typically contain a variety of feedstuffs because no single ingredient is able to supply all the necessary amino acids in the right levels. Protein and amino acid requirements vary considerably according to the productive state of bird, that is, the rate of growth or egg production.
The main sources of protein in poultry diets are plant proteins such as soybean meal, canola meal, corn gluten meal, and so on. Animal proteins used include fishmeal and meat and bone meal. Fishmeal can be used only in limited quantities (less than 5% of the total composition of the diet) or it will give poultry meat and eggs a fishy flavor.
Minerals
Minerals play a role in bone formation, but minerals are also needed for several other important functions, including formation of blood cells, blood clotting, enzyme activation, and energy metabolism and for proper muscle function. Minerals are the inorganic part of feeds or tissues. They are often divided into two categories, based on the amount that is required in the diet. Requirements for major, or macro, minerals usually are stated as a percentage of the diet, whereas requirements for minor, or trace, minerals are stated as milligrams per kilogram of diet or as parts per million.
The microminerals include copper, iodine, iron, manganese, selenium, and zinc. Although poultry have lower requirements for microminerals, these minerals play essential roles in the body's metabolism. Iodine, for example, is required to produce thyroid hormones that regulate energy metabolism. Similarly, zinc is involved in many enzyme-based reactions in the body, and iron aids oxygen transportation within the body.
The macrominerals include calcium, phosphorus, chlorine, magnesium, potassium, and sodium. Many people are familiar with calcium's role in proper bone formation and eggshell quality, but calcium's important role in blood-clot formation and muscle contraction is less well known. Phosphorus is important in bone development, and it is part of cell membranes and is required for many metabolic functions. Chlorine is important in the formation of hydrochloric acid in the stomach and thus plays a role in digestion. Sodium and potassium are electrolytes important for metabolic, muscle, and nerve functions. Magnesium also assists with metabolic and muscle functions.
Vitamins
Vitamins are generally classified under two headings: fat soluble vitamins, A, D, E and K, and water-soluble vitamins, that include the so called B-complex and vitamin C (ascorbic acid). Vitamin C is synthesised by poultry and is, accordingly, not considered a required dietary nutrient.
Some vitamins are produced by microorganisms in the digestive tract. Vitamin D can be produced when sunlight hits the bird's skin. Other vitamins must be supplied because they are not formed by the birds. Many essential vitamins are partially supplied by feed ingredients such as alfalfa meal and distillers' dried solubles. A vitamin premix is typically used to compensate for the fluctuating levels of vitamins found naturally in food and to assure adequate levels of all vitamins.