a comprehensive resource of avian nutrition research for captive bird populations

Nutritional Elements

The main nutritional elements are termed Macro-Nutrients and are Proteins, Carbohydrates (Sugars), Fats (Lipids) and Fibre. These make up the main bulk of the diet. Vitamins and Minerals are required in smaller quantities and are termed Micro-Nutrients.


Although not classed as a nutrient, water is probably the most important substance to the overall functioning of the body. Tap water varies greatly from area to area with regards to its chemical composition, apart from what the Water Companies choose to add. Hard water can contain up to 10 times more Calcium than that from soft water areas for example. Some thought should be given if mineral supplements are to be added to the drinking water. Your local water company will supply a detailed analysis of your supply online. Bottled Spring/Mineral Water can be used on a small scale, but again the chemical composition requires checking. This can usually be found on the reverse of the label. Rain water collected from roof systems could be contaminated by bird droppings or pick up leached chemicals from the environment. Drinking water provided to birds with added vitamins/supplements can cause the bacterial count to multiply 100 times in a 24 hour period. A Biofilm can form on the walls of the container and this will not be removed by rinsing alone, but requires a thorough wash and disinfection.


Proteins are complex molecules formed from varied combinations of Amino Acids. These Amino Acid molecules are composed of Carbon, Oxygen, Hydrogen, Nitrogen and occasionally Sulphur.

The simplest Protein molecules are composed of chains of Amino Acids, which are termed Polypeptides. Complex Proteins are produced when these chains fold on themselves, form spirals, twist or entwine or a combination of each. 20 Amino Acids are used by the body to produce Protein. 9 are termed "Essential" because there are no metabolic pathways available to allow their synthesis and they need to be supplied from the diet. These 9 Amino Acids are: - Arginine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine. Histidene, Glycine and Proline can be synthesised by the body, but in insufficient quantity to supply the needs of growing birds. These are termed "Conditional". The remaining 8 are termed "Non-essential" as they can be synthesised in sufficient quantities to meet all the requirements of the bird. They are Alanine, Asparagine, Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Serine and Tyrosine (Klasing 1999).

Functions of Protein

  1. Protein can be used as a source of energy for the body, when Carbohydrates and Fats are unavailable.
  2. Proteins are the major component of Muscles, Feathers, Skin and Connective Tissue. Keratin and Collagen for example.
  3. Proteins are the major component of the enzymes, which catalyse chemical reactions in the body. Amylase and Trypsin for example. Hormones are also synthesised from Protein. Insulin for example.
  4. Protein Molecules are involved in the transport of various chemicals around the body. Haemoglobin (Oxygen) and Transferrin (Iron) for example.
  5. Protein is involved in the production of Antibodies, which play an important role in the Immune system.
  6. Proteins help to maintain the fluid balance (amount of water) within cells.
  7. Proteins help to maintain the pH of the cells and tissues because of its buffering capacity.

Sources of Protein

Meat, fish, poultry, eggs and dairy foods usually contain the full range of Amino Acids required by the body. Vegetables/fruits are less likely to contain all of the required Amino Acids, so a more varied selection of items should be offered.

Toxicity/Deficiency of Protein

A high Protein diet over a long period of time may cause kidney failure and bone degradation. Deficiency is more likely to affect young growing birds, where weight loss and muscle wastage could occur.


K. C. Klasing 1999 Comparative Avian Nutrition 133-170 CAB International

Carbohydrates/Dietary Fibre

Carbohydrates are also known as Saccharides. Carbohydrates are usually composed of the elements Carbon, Hydrogen and Oxygen in the ratio of 1:2:1 and it is from this that the name is derived. Sugars, starches and cellulose are forms of Carbohydrates. In their most basic form Carbohydrates are simple sugars or monosaccharides such as Glucose. These simple sugars can combine in pairs to form disaccharides such as Lactose, which is composed of Glucose and Galactose. Carbohydrates with 3 to 10 simple sugars in combination are termed Oligosaccharides and those with a larger number Polysaccharides for example Starch. Many Dietary Fibres are Carbohydrates, such as Cellulose from plant cell walls and Chitin from Arthropod exo-skeletons. The dietary fibres normally pass through the alimentary tract undigested, but certain adaptations do manage to utilize them to some extent. The Ceacum is one adaptation which provides a site for bacteria to digest these fibres. Insectivorous birds produce the enzyme Chitibiose which is able to break down Chitin into simpler carbohydrates.

Functions of Carbohydrates

  1. Source of energy. The vast majority of Carbohydrates are eventually broken down by various enzymatic processes into Glucose. This is the main source for energy production within the body of the bird.
  2. Ribose and Deoxyribose are part of the chemical structure of DNA and RNA.
  3. The Polysaccharide Glycogen is a source of energy storage. The main stores are within the liver and muscles, and when required by the body it is converted to Glucose by the action of the hormone Glucagon. The reverse action is controlled by the hormone Insulin.
  4. Dietary Fibres aid in bulking out the faeces, buffering the pH and aiding the food bolus to pass through the digestive tract.
  5. Carbohydrate which can be fermented in the lower intestine, rectum and Caeca (if present) stimulate the growth of the gut microflora. Fructo-oligosaccharides have been shown to stimulate the growth of Bifidobactium species. This can aid the inhibition of pathogens by Competitve Exclusion. Fructo-oligosaccharides are often to be found in the pelleted avian food now available. See section on Probiotics for more information.

Sources of Carbohydrates

Cereals, Root Vegetables, Vegetables, Fruit, and Dairy Products. Exoskeletons of Arthropods such as Beetles, Butterflies and Crickets/Locust.

Toxicity/Deficiency of Carbohydrates

A totally carbohydrate free diet will cause the body to break down protein/fat as an energy source. These can lead to the production of excess Ketones, which eventually have a toxic effect on the liver. It only takes a small amount of carbohydrate in the diet to alleviate these symptoms.

Carbohydrates are not known to be toxic, although diets high in Monosaccharides/Disaccharides can cause obesity.

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