We discussed access to feeding food and poultry in impoverished countries in the previous post. Today, we want to find out which nutrients are required for poultry growth nowadays.
For maximum growth and health, highly reared poultry need a balanced set of nutrients in their diet. The nutrients birds need vary depending on the species, age, and purpose of production whether the birds are kept for meat or egg production.
Poultry need nutrients to maintain their current state (maintenance) and the possibility of body growth (weight gain) or egg production. Birds need a constant source of energy, protein, essential amino acids, essential fatty acids, minerals, vitamins and most importantly water. Poultry get the energy and nutrients they need through digestion of natural foods, but minerals, vitamins, and some key essential amino acids (lysine, methionine, threonine, and tryptophan) are often offered as artificial supplements.
Poultry can get energy from simple carbohydrates, fats and proteins. They cannot digest and use some complex carbohydrates such as fiber, so the feed formulation must use an energy-based system. Metabolizable energy is the standard measure of the energy content of feed ingredients and poultry needs. This takes into account the loss of energy in the stool and urine. Birds basically eat to meet their energy needs, provided the diet is adequate for other essential nutrients. Therefore, the energy level in the diet is one of the main determining factors in poultry feed consumption. As the energy level of the diet changes, feed intake changes and the characteristics of other nutrients must be adjusted to maintain the required intake. For this reason, the energy level of the diet is often used as a starting point in the formulation of practical diets for poultry.
Different classes of poultry require different amounts of energy for metabolic purposes, and its deficiency affects production performance. To maintain high productivity, new poultry species are usually fed relatively high-energy diets. Dietary energy levels used in a particular situation are largely determined by the availability and cost of energy-rich foods. Due to the high cost of cereals, especially corn, the use of low-energy diets to feed poultry is not uncommon in many developing countries.
Protein and amino acids
The function of dietary protein is to provide amino acids for the maintenance, muscle growth and synthesis of egg protein. Muscle and egg protein synthesis requires the supply of 20 amino acids, all of which are physiological needs. Ten of these are either not synthesized at all or are synthesized too slowly to meet metabolic needs and are identified as essential elements of the diet. These should be included in the diet. Equilibrium can be synthesized from other amino acids. These elements are referred to as non-essential dietary elements and do not need to be considered in the feed formulation. However, from a physiological point of view, all 20 amino acids are essential for the synthesis of various proteins in the body. Essential amino acids for poultry include lysine, methionine, threonine, tryptophan, isoleucine, leucine, histidine, valine, phenylalanine and arginine. In addition, some consider glycine essential for young birds. Cysteine and tyrosine are considered semi-essential amino acids because they can be synthesized from methionine and phenylalanine, respectively. Of the ten essential amino acids, lysine, methionine, and threonine are the most limited in most practical poultry diets.
Poultry do not need protein per se. However, adequate nitrogen supply from dietary protein is essential for the synthesis of non-essential amino acids. Poultry amino acid requirements are affected by various factors including production level, genotype, sex, physiological status, environment, and health status. For example, high levels of lean meat deposition require relatively high levels of lysine. High levels of egg output or full growth require relatively high levels of methionine. However, most changes in amino acid requirements do not result in changes in the relative proportions of different amino acids. Therefore, there is an ideal balance of dietary amino acids for poultry, and changes in amino acid requirements are usually expressed in terms of balanced protein or ideal protein.
Fats and fatty acids
Because fat has a higher energy density than carbs and protein, fat is commonly used in chicken diets to obtain the required dietary energy concentration. In most practical diets, fat makes up 3 to 5% of the total calories. Other advantages of fats include enhanced dust control in feed mills and poultry houses, as well as improved diet palatability. Poultry does not have a specific demand for fats as a source of energy, however it has been shown that they do require linoleic acid. Linoleic acid is the sole necessary fatty acid required by chicken, and its insufficiency has only been seen in birds fed realistic diets on rare occasions. The main effect of linoleic acid in laying birds is on egg size.
Minerals are required for the creation of the skeletal system, general health, metabolic activity, and the preservation of the body’s acid-base balance. Calcium and phosphorus, together with sodium, potassium, chloride, sulfur, and magnesium, are the most prevalent mineral elements in the body and are categorized as macro-minerals. Macro-minerals are elements that must be consumed in amounts greater than 100 mg/kg.
Calcium and phosphorus are required for the formation and maintenance of skeletal structure as well as the quality of the egg shell. In average, phytate-phosphorus accounts for 60 to 80 percent of total phosphorus in plant-derived components. Due to the lack of endogenous phytase in fowl digestive enzymes, phytate phosphorus is poorly used under typical dietary conditions. Because around one-third of the phosphorus in plant feedstuffs is non-phytate and therefore biologically accessible to chickens, the phosphorus requirement for poultry is given as non-phytate phosphorus rather than total phosphorus. In order to maximize calcium and non-phytate phosphorus absorption in growing birds, a 2:1 ratio must be maintained in their diets. Because of the significant requirement for calcium in laying birds’ diets for optimal shell quality, the ratio is 13:1.
The acid-base balance in the body is mostly determined by the dietary proportions of sodium (Na), potassium (K), and chloride (Cl) for maintaining the physiological pH. When the pH of the body shifts from acid to base, metabolic activities are adjusted to maintain the pH, resulting in decreased performance. The dietary electrolyte balance is represented as mEq/kg food and is described by the simple formula (Na+ + K+ – Cl-). Electrolyte imbalance must be avoided at all costs, especially in hot regions. Under most circumstances, a diet balance of roughly 250 mEq/kg appears to be sufficient for optimal growth. It’s crucial to have a good balance between these three minerals and their concentrations. Their dietary levels must all be within acceptable ranges, not insufficient or excessive, in order to them to be effective. Heat-stressed birds drink more water and are better able to survive the heat if the water contains electrolytes. Under these circumstances, replacing some of the additional dietary sodium chloride with sodium bicarbonate has proven to be beneficial.
Copper, iodine, iron, manganese, selenium, zinc, and cobalt are trace elements that serve as components of bigger molecules and cofactors of enzymes in a variety of physiological reactions. Because normal cereal-based diets are low in several major and trace minerals, they should be supplemented in practical poultry diets. Some trace minerals are now available in organic forms, which are thought to have a higher biological availability than inorganic forms.
Water is the most critical nutrient in poultry nutrition, but it is also the most overlooked. Water affects the bird’s physiological functions in almost every way. The digestion of feed, the absorption of nutrients, the elimination of waste materials, and the regulation of body temperature all require a steady supply of water. Water makes up around 80% of the human body. Poultry, unlike other animals, eats and drinks continuously. Production and growth are irreparably harmed if they are deprived of water for even a short period of time. As a result, water must be always available. Water intake is significantly associated with feed intake and development rate.
Water requirements are difficult to predict and are impacted by a variety of factors, including ambient conditions, bird age, and physiological health. Water intake is typically thought to be twice that of feed intake under most circumstances. Temperatures in drinking water should range from 10 to 25 degrees Celsius. Consumption will be reduced if the temperature rises over 30 °C.
The quality of the water is also critical. Water quality is typically taken for granted, yet it can lead to decreased productivity and significant financial losses. Water is a great medium for the spread of contaminants like chemicals and minerals, as well as the growth of hazardous microbes. In dry and semi-arid places where water is scarce, water quality for poultry can be a serious issue. Birds tolerate saline drinking water with less than 0.25 percent salt, but if water intake is restricted, sodium poisoning can occur.
National Research Council. 1994. Nutrient requirements of poultry, 9th revised edition. Washington, DC, National Academy Press.
Leeson, S. & Summers, J.D. 2005. Commercial poultry nutrition, 3rd edition. Nottingham, UK, Nottingham University Press.
Ravindran, V. & Bryden, W.L. 1999 Amino acid availability in poultry in vitro and in vivo measurements. Australian Journal of Agricultural Research, 50: 889–908.
Scanes, C.G., Brant, G. & Ensminger, M.E. 2004. Poultry science. Upper Saddle River, New Jersey, USA, Pearson Prentice Hall.