Dr. Jacquie Jacob Ph.D., University of Kentuckky
As with all animals, poultry species have specific nutritional needs. The nutrient requirements of a flock are determined by several factors:
- Genetics (species, breed, or strain). Different species (e.g., chickens, turkeys, ducks) have different average body sizes, growth rates, and production levels. They also differ in how efficient they are at digesting and absorbing different feed ingredients. Even within a species there can be differences among breeds (e.g., meat chickens versus egg-laying hens).
- Age. Nutrient requirements are influenced by body weight and life stage (e.g., starter, growing, egg-laying).
- Sex. The nutrient requirements of male and female birds are similar at hatch but differences develop as the flock gets older, when males consume more than females.
- Reproductive state. The level of egg production in hens, and sexual activity in males, affects nutrient requirements of the flock.
- Environmental temperature. Poultry have increased energy requirements in cold weather, as more energy is needed to maintain normal body temperature. Conversely, energy requirements decrease in hot weather.
- Management system. Housing design influences the level of activity of the flock, and therefore its energy requirements.
- Health status. Flocks dealing with disease may benefit from increased dietary vitamin levels.
- Production aims. The nutrient composition of the poultry diet varies according to production aims, which can include optimal weight gain or carcass composition, as well as egg numbers or egg size.
Commercially prepared organic feeds are available for the specific type and age of bird in production. It is important to provide the right type of feed. Feeding a layer ration, which is high in calcium and lower in protein, to young birds can cause serious health issues. Or, feeding a starter/grower feed to laying hens will drastically reduce egg production.
Flocks with access to pasture may supplement their diets with greens and insects, depending on the quality of the pasture. A flock will quickly devour the greens within an enclosed area, so pasture rotation is essential to maintain forage quality.
Poultry consume feed to meet their energy requirements, assuming that the diet is adequate in essential nutrients, so their daily feed intake will depend on the energy content of the diet. A high density feed has a high energy level. Since the flock will consume less feed, the nutrients must be more concentrated in the amount of feed they will consume in a day. Similarly, a low density diet has a low energy level, and the flock will consume more of the feed daily. The required levels of the different nutrients will depend on the energy level of the diet.
Energy is not a nutrient, but rather a property of energy-yielding nutrients such as carbohydrates or fats. Not all the energy in a feed ingredient is used completely. The energy value of a feed ingredient is typically expressed as metabolizable energy (ME). The ME is the gross energy content of the feed ingredient minus the gross energy lost in the feces and urine. Stated another way, ME is calculated as the energy coming in one end and the energy going out the other end. The energy levels are expressed as kilocalories of ME per kilogram or pound.
Dietary protein requirements are actually requirements for the amino acids that make up the protein. There are 22 amino acids in body proteins, all of which are physiologically required. Some of the amino acids can be produced from other amino acids and are considered non-essential. Essential amino acids are those that poultry cannot produce, or cannot produce in sufficient quantities. The two main essential amino acids that impact poultry fed a corn-soybean meal diet are methionine plus cystine (referred to as the sulfur amino acids) and lysine. The other essential amino acids may become deficient when other feed ingredients are used. When using alternative feed ingredients, therefore, it may be necessary to evaluate levels of arginine, glycine, histidine, isoleucine, leucine, phenylalanine, serine, threonine, tryptophan, tyrosine, tryptophan or valine.
Specific Nutrient Requirements
A National Research Council (NRC) publication on the nutrient requirements of poultry was published in 1994. Although the information is over 20 years old, it is still referred to today. However, the fast growth rates and production levels of today's poultry stocks have warranted a modification of the nutrient requirement profiles. Furthermore, the criteria used for developing nutrient requirements have changed. The NRC requirements were developed with maximum production as the main assessment criterion. Today, additional criteria have become important, including maximum health and welfare and minimal environmental impact.
Nutrient requirements for dual-purpose breeds such as Barred Plymouth Rock and Rhode Island Red have not yet been developed.
References and Citations
- National Research Council. 1994. Nutrient requirements of poultry. 9th revised edition. National Academy Press, Washington, D.C. (Available online at: http://www.nap.edu/openbook.php?record_id=2114&page=R1) (verified 2 September 2013)