Avian Nutrition:
Avian nutrition glossary

Author: Christal Pollock, DVM, Dipl. ABVP-Avian

Date: June 15, 2007

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A

AAFCO	See the Association of American Feed Control Officials
Acetate	Primary volatile or short-chain fatty acid produced during bacterial fermentation of fiber. Energy may be derived from its metabolism.
Acetic acid	See Acetate
Aflatoxin	Mycotoxins produced by Aspergillus flavus or A. parasiticus growing on corn, peanuts, or cottonseed.
African Grey parrots	Susceptible to a hypocalcemic syndrome associated with weakness, ataxia, and seizure activity. Although pathogenesis is unknown, hypocalcemia may result from an inability to mobilize bone rapidly.
Airplane wing	See Angel wing
Alanine	Nonessential amino acid
Albumin	Globular proteins found in egg white and blood plasma.
Alloenzymatic digestion	Digestion using microbial assistance such as digestion of plant fiber
Allocholic acid	Major bile acid of faunivores
Alpha-carotene	Dietary carotenoid
Alpha-tocopherol	Most biologically active form of vitamin E with relatively little antioxidant efficacy.
Altricial	Species which hatch with closed eyes, little down, and poor musculature. Require extensive parental assistance and grow very quickly post-hatch.
Amino acid	Molecule composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur or phosphorus atoms. Although hundreds of amino acids exist, only 20 are commonly found as components of protein.
Amino acid antagonism	Surplus of one amino acid increases the requirement for a metabolically similar amino acid (ex: high dietary lysine increase the need for arginine)
Amino acid, Essential	Essential amino acids in the bird include arginine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Histidine, glycine, and proline are essential in growing chickens. Research suggests that glycine is also essential in budgerigars.
Amino acid, Non- essential	Amino acids which may be synthesized from nitrogen (alanine, asparagine, cysteine, glutamine, serine, and tyrosine.
Ammonia	Compound excreted by chickens on very high protein diets in addition to uric acid.
Amylase	An enzyme which breaks down starch into glucose molecules. Secreted by the salivary glands of some granivores (i.e. present in the House Sparrow, but not the chicken) and secreted by the pancreas in amounts which vary with the diet in chickens.
Amylopectin	A component of starch.
Amylose	A component of starch.
Angel wing	A disease of captive waterfowl in which the wing is rotated outward at the carpus also known as “airplane wing”. Although the pathogenesis is unknown, excess dietary protein, rapid growth, low dietary calcium, hypovitaminosis D, manganese deficiency, vitamin E deficiency, heredity, restricted exercise, and incorrect incubation have all been theorized.
Antioxidant	Any substance that helps preserve food by retarding deterioration, rancidity, or discoloration caused by oxidation.
Apparent metabolizability	Energy values of a bird food may be expressed as: nutrient intake - nutrient in droppings)/nutrient intake
Apparent metabolizable energy	Energy or nutrient intake minus energy in excreta (urine, feces, egested pellets). This value is apparent because it is biased by excreta that has nothing to do with food consumption such as sloughed intestinal epithelial cells.
Arabinose	A monosaccharide containing five carbon atoms or pentose.
Arachidonic acid	A conditionally essential fatty acid in chickens, required when there is insufficient linoleic acid in the diet. A member of the omega-6 fatty acid family found in animal fats, particularly fish oils. It has been theorized that carnivorous birds may require arachidonic acid as in mammals.
Arginine	Essential amino acid of birds used to create creatine and polyamines. Deficiency causes an upward curling of the remiges (wing feathers) in chicks.
Ascorbic acid	See Vitamin C
Ascorbyl palmitate	Fat-soluble form of vitamin C used as a natural antioxidant.
Asparagine	Nonessential amino acid of birds
Aspartate	Nonessential amino acid of birds
Association of American Feed Control Officials (AAFCO)	Government organization that oversees pet food production
Astaxanthin	Dietary carotenoid pigment found in microalgae, krill, and shrimp. This pigment is used naturally and commercially in flamingos to provide color.
Atwater factors	See modified Atwater factors
Avi-Cakes	Lafeber Company product containing whole grains and seeds mixed with a pellet to create a balanced product.
Avidin	Compound in raw egg white which binds biotin making it unavailable for absorption. Cooking destroys avidin.
Avocado (Persea spp.)	Food item to avoid in birds including the leaves. Some species may be toxic causing cardiomyopathy and death. Pathogenesis is unclear.

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B

B6	See Pyridoxine
B12	See Cobalamin
Balanced	Label term that refers to required nutrients present in the proper amounts and proportions based upon recommendations from recognized authorities
Basal metabolic rate (BMR)	Minimal energy expended by a normal, resting bird in a thermoneutral environment. The BMR (kcal/d) of a tropical parrot is 73.6 X BW (kg)0.73.
Basal nutrient requirements	Nutrients needed to maintain basic life functions (replaces losses inherent in being alive)
BCAA	See Branched chain amino acids
BCS	See Body condition score
Beak	See Bill
Beta-carotene	Dietary carotenoid that serves as a vitamin A precursor or pigment in some species. Found in dark green, yellow, and orange fruits and vegetables. Mammalian carnivores cannot utilize beta-carotene and the same may hold true for birds.
Beta-cryptoxanin	Dietary carotenoid
Beta-glucan	Dietary fiber found in oats and barley.
Beta-phocacholic acid	Major component of bile in ducks, geese, and flamingos
BHA	See Butylated hydroxyanisole
BHT	See Butylated hydroxytoluene
Bile	Green liquid made in the liver that enables fats to mix with water.
Bile acids	Steroid acids such as allocholic acid, chenodeoxycholic acid, cholic acid and deoxycholic acid which are a part of bile. Produced by the liver from cholesterol and secreted into the intestines in the form of salts.
Bile ducts	Carry bile salts, cholesterol, and phospholipids into the duodenum. Opening varies among species. In pigeons, one duct enters the anterior duodenal loop and the second enters the posterior duodenum. In some species, the right duct enters a gallbladder.
Bile salts	Detergent-like compounds that help to emulsify fatty foods for proper digestion and absorption.
Bill	External anatomic structure of birds used for eating, grooming, manipulating objects, probing for food, and feeding young. Also known as the beak or rostrum.
Bioavailability	Describes the degree to which a nutrient can be absorbed and utilized for its required purpose from a particular source. Usually expressed as a percentage of an established standard.
Bioflavonoids	A group of red, blue, and yellow pigments with vitamin-like activity best know for their antioxidant activity. Consist of over 4,000 different compounds excluding carotenoids usually found naturally as glycosides linked to sugars. Highest levels are found in the skin of colored fruits and vegetables.
Biologic value	The percentage of absorbed protein retained by the body, and a crude measure of the body’s ability to convert absorbed amino acid into body tissue.
Biotin	Sulfur-containing B-vitamin synthesized by cecal flora and found in dietary sources such as liver, egg yolk, nuts, beans, and cereals such as barley and wheat. Stored in the liver. Serves as a coenzyme in several carboxylation reactions. Deficiency is rare but may develop with oral antibiotic use. Signs of deficiency may include poor growth, dermatitis of the feet, necrosis of toes, swollen eyelids, lethargy, and neurologic deficits in chicks. Deficiency may also play a role in fatty liver and kidney syndrome in adult birds.
Black tongue	See Pellagra
Body condition scoring (BCS)	Subjective assessment of body fat and musculature, which should be recorded at the same time as body weight in grams. Scoring should take into account life style, age, and species. The “generic” bird with an optimal body condition score has a good overall appearance and a pectoral muscle contour appropriate for the species.
Bomb calorimetry	Calorimeter used to measure the amount of energy retained in tissues, eggs, or feathers by burning the material and measuring the total amount of heat produced.
Bone meal	A mixture of crushed and ground bones no longer popular as dietary calcium supplement due to the possible presence of contaminants.
Branched chain amino acids (BCAA)	Leucine, valine, isoleucine; Diets enriched in BCAA have been used to theoretically normalize plasma amino acid levels in humans in the hope of improving nitrogen balance and hepatic encephalopathy
Bulk	Feature of plant material related to its ability to hold water. Bulk shortens transit time and can decrease nutrient digestibility.
Butylated hydroxyanisole (BHA)	Synthetic antioxidant with relatively high efficacy.
Butylated hydroxytoluene (BHT)	Synthetic antioxidant with relatively high efficacy.
Butyrate	Volatile or short-chain fatty acid produced by bacterial fermentation of fiber. Energy may be derived from its metabolism.
Butyric acid	See Butyrate

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C

Calciferol	See Cholecalciferol
Calcium	The most abundant mineral in the body necessary for bone mineralization and eggshell calcification. Dietary sources include bone, soybean meal, and flaxseed meal. Free-ranging birds supplement their diet with mollusk shells, eggshells, and calciferous grit. Egg-laying chickens require 3.3% calcium, while egg-laying budgerigar parakeets and cockatiels require 0.85% and 0.35% calcium respectively. The calcium requirement for growing chicks is approximately 1.0%. The maintenance calcium requirements for chickens is less than 0.1% of diet.Calcium deficiency occurs when the diet contains excess phosphorus or too little calcium or vitamin D. Calcium deficiency may lead to skeletal deformities, particularly in growing birds, egg binding, dystocia, weakness, ataxia, or seizure activity. A hypocalcemic syndrome has been documented in African Grey parrots. Excess dietary calcium is less common but results in mineralization of tissues, particularly the kidneys.
Calcium chloride	Texturizer added to canned foods to keep them from turning mushy.
Calcium:phosphorus ratio	1.5 to 2:1 is recommended, however ratios between 1.4:1 and 4:1 are adequate assuming dietary vitamin D levels are sufficient.
Calcium propionate	Preservative which serves as a mold inhibitor.
Calorie	The term commonly substituted for kilocalorie.
Canary seed	Non-oil seed frequently fed to small granivores to increase the protein in a seed mixture.
Cane molasses	The product is 50% sugars, making it extremely palatable. Although it is a liquid, it is very high in solids (75%). Reduces dust in a mixture, aids pelleting, and is a good source of minerals
Canola oil	A “heart-healthy” oil containing omega-6 and omega-3 fatty acids in a ratio off 2:1. Second to flax oil in omega-3 fatty acid. Also known as rapeseed oil.
Canola seeds
Canthaxanthin	Dietary carotenoid pigment found in green algae, fish, and crustacea. Used naturally and commercially in flamingos and other pink or red birds to provide color.
Carbohydrate	A principal dietary source of energy derived from plants. Classified as monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The energy value of dietary carbohydrates is about 4 kilocalories per gram.
Carnivore	Type of faunivore that consumes terrestrial vertebrates.
Carnitine	L-carnitine transports long-chain fatty acids and is needed for maximal chick growth. Synthesized primarily in the liver from lysine and methionine and stored in skeletal and cardiac muscles. Although deficiency is often asymptomatic, signs may include chronic muscle weakness, hypoglycemia, cardiomyopathy, and hepatomegaly. L-carnitine has also been anecdotally recommended in the treatment of lipomas in budgerigar parakeets.
Carotene	See Beta-carotene
Carotenoids	Group of dietary pigments found in orange and green vegetables and highly pigmented fruits. Carotenoids may also be obtained from some species of insect, mollusk, shrimp, or fish that further concentrate and modify carotenoids. Serve as vitamin A precursors in chickens and provide feather coloration in a variety of species such as the flamingo, ibis, trogon, tanager, and Gouldian finch. Carotenoids found in the greatest number in food include beta-carotene, alpha-carotene, lutein, lycopene, beta-cryptoxanin, zeaxanthin, canxanthin, and astaxanthin.
Carry-through	A property of preservatives related to retention of antioxidant function after being subjected to the heat, pressure, and moisture of food processing. Most natural preservatives (i.e. ascorbic acid, mixed tocopherols, ascorbyl palmitate) have poor carry-through.
Casein	Protein found in dairy products such as milk and cheese; also used as a binding agent in many food items
CCK	See Cholecystokinin
Ceca	A pair of diverticula connected to the proximal colon and the ileum where fermentation of poorly digestible carbohydrates occurs. Relatively large in herbivores like galliforms, waterfowl and ratites. Absent or vestigial in psittacines and passerines.
Cecotropes	Nutrient-rich, light brown, homogenous material emptied from the cecum by major reverse peristaltic contractions. Passed once or twice daily in galliforms. Also known as cecal feces.
Cecotrophy	Ingestion of cecotropes practiced by some birds.
Cecum	See Ceca
Celiac disease	A chronic, maldigestive/malabsorptive disease of the mammalian intestinal tract associated with an inability to tolerate gluten. Also known as celiac sprue or gluten-sensitive enteropathy.
Cellulose	Polysaccharide found in the cell wall of leaves, roots (i.e. carrots), bran, whole wheat, and beans. This insoluble fiber is fermented for energy in species with developed ceca.
Chemical score	Index of protein quality that compares amino acid profiles. Egg protein is often the reference protein and is given a score of 100. The amino acid with the greatest deficit is called the limiting amino acid.
Chenodeoxycholic acid	Major bile acid of many wild birds
Chitin	Mucopolysaccharide within the exoskeleton of many invertebrates.
Choanal slit	Median slit in hard palate of birds which connects the oropharynx and the nasal cavity.
Cholecalciferol	Form of vitamin D3 used by birds. Synthesized from 7-dehydroxycholesterol in the skin when exposed to ultraviolet light or ingested from dietary sources such as egg yolk, fish oil and a number of plants.
Cholecystokinin (CCK)	A peptide hormone of the gastrointestinal tract responsible for stimulating the digestion of fat and protein.
Cholesterol	A lipid compound derived from sterol present in all parts of the body including the nervous system, skin, muscle, liver, intestines and heart. Cholesterol is made in the liver and obtained from animal products in the diet. In the blood stream, cholesterol combines with fatty acids to form high-density (HDL) ,low-density (LDL), and very-low-density lipoproteins (VLDL).
Cholic acid	Major bile acid of faunivores.
Choline	B-complex vitamin synthesized in the bird liver from serine. Unique in that large amounts are needed in the diet (>1%). Dietary sources include egg yolks, organ meat, legumes, and grains. Choline serves as a basic part of the cell membrane phospholipid, lecithin.
Chondrodystrophy	Condition characterized by hock (tarsometatarsal) joint swelling, twisting of the distal tibiotarsus or proximal tarsometatarsus, and slipping of the gastrocnemius tendon. May be caused by manganese, biotin, or choline deficiency in poults and chicks. Also known as perosis or slipped tendon.
Chloride	Principle extracellular anion.
CHO	Abbreviation for carbohydrate based on the fact that compounds are made primarily from carbon atoms and water.
Chromium	Trace element present in several enzymes that metabolize fat. Dietary sources include liver, wheat germ, and broccoli. There are variable results on the performance of poultry given chromium, however chromium has been used to lessen the toxic effects of vanadium in chicks.
Chylomicron	Fat globule composed of protein and lipid that transports fat in the blood from where it enters circulation in the intestine to the liver or adipose tissue.
Chyme	Partially digested liquid that exits the stomach.
Citric acid	Natural antioxidant found in citrus fruits often used in combination with other naturally-derived antioxidants.
Cloaca	Common chamber and outlet which receives the gastrointestinal, urinary, and reproductive tracts.
Cobalamin	Vitamin B12 or cyanocobalamin is the only vitamin that contains a trace element, cobalt. B12 is synthesized almost exclusively by bacteria, but it may also be obtained from animal origin sources (organ meat, fish). Excess amounts may be stored in the liver (and to a much smaller degree in muscle, bone, and skin). Deficiency is very rare but may result in poor growth neuropathies, anemia, gizzard erosion, perosis, fatty heart, liver, and kidney
Cobalt	Trace element found in cobalamin or vitamin B12
Collagen	Fibrous proteins present in connective tissue; converted to gelatin with prolonged boiling.
Colon	see Rectum
Complementarity	The matching of foods to improve the proteins fed (i.e. Rice is low in lysine and beans are low in methionine. Eating beans and rice together improves the proteins fed).
Complete	Term used on labels which states that feed is nutritionally adequate. The product may be fed as a sole ration and is capable of maintaining life and/or promoting production alone.
Complete protein	Protein source that contains ample amounts of all essential amino acids.
Complex carbohydrates	See Polysaccharides
Contraction sequence	Pattern of gastrointestinal contraction varies widely among avian species but normally includes duodenal reflux in those species studied (i.e. parrots, fowl, ostrich, petrels, raptors). Reflux appears to improve intestinal digestion of nutrients.
Controlled hypothermia	Small birds in cool climates may decrease their energy needs overnight by reducing body temperature between 25 to 35°C. See torpor.
Copper	Trace element absorbed by the intestinal tract and metabolized within the liver. Used for iron absorption, transport, and hemoglobin formation. Also serves as an antioxidant, promotes the growth of strong bones, and protects the health of nerve tissue. Most organ meats are rich in copper. Deficiency may lead to anemia, bleeding, lameness, infertile eggs, poor feather pigmentation, dissecting aortic aneurysms or cardiac hypertrophy in poultry and ratites. Chronic hepatitis and severe cholestasis have been associated with the hepatic accumulation of copper in the dog.
Coprodeum	Anterior component of the cloaca that receives the gastrointestinal tract.
Coprophagy	Ingestion of rectal or cecal feces.
Corn	Grain rich in methionine and cysteine. Its first limiting amino acid is lysine. Diets high in corn should be supplemented with niacin as niacin in corn is bound and unavailable for absorption.
Crop	Diverticulum or widening of the esophagus lined with thick, cornified epithelium. Mucus gland secretions soften food.
Crop milk	A semi-solid substance secreted by the pigeon crop which parents feed to their young by regurgitation. High in protein and fat, low in calcium and carbohydrate.
Cruciferous vegetables	Brassica vegetables which contain sulfur compounds such as broccoli, cauliflower, turnips, and kale. Excellent sources of indoles, dithiolthiones, isothiocyanates and chlorophyllins which are theorized to possess potent anti-cancer properties.
Crude fiber	Old-fashioned term that refers to the remnants of plant fiber that remain after the extraction process. Crude fiber underestimates the amount of hemicellulose, and therefore the amount of dietary fiber, in food.
Crustacivore	Species which feed on large numbers of crustaceans (i.e. crab plover, some rails, penguins, auks)
Culmen	Dorsal midline of the upper beak.
Curly toe paralysis	Flexion of digits with toes curled under which may occur in chicks with riboflavin deficiency.
Cuticle	Glycoprotein matrix that protects the inner surface of the ventriculus.
Cuttlebone	Source of dietary calcium
Cuttlefish bone	See Cuttlebone
Cyanide	Chemical compound present in apple seeds as well as cherry, plum, apricot, and peach pits.
Cyanocobalamin	See Cobalamin
Cysteine	Nonessential amino acid of birds created by degradation of methionine. Feathers and eggs are rich in cysteine.

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D

Dabbler	Technique of obtaining food in which a duck submerges its head and neck or tips up in various water substrates to feed on vegetable matter (Subfamily Anatinae)
Daily metabolizable energy requirement	The amount of energy expended through oxidation of nutrients and energy retained in tissues = maintenance metabolizable energy requirement + additional metabolizable energy needed for deposition of products such as body tissue, feathers, eggs
Daily requirement	Method of expressing dietary requirement based on intake (mg/day or mg/kg BW/day)
DE	See Digestible energy
7-dehydroxycholesterol	Cholesterol in skin converted to vitamin D3 when exposed to ultraviolet light. Chickens require 11 to 30 minutes of strong sunshine daily for adequate vitamin D.
Delta-tocopherols	Fraction of vitamin E with low biologic activity but relatively high anti-oxidant efficacy.
Dextrose
DHA	See Docosahexanoic acid
Diabetes mellitus	An endocrine disease that is not completely understood in birds, however in granivorous species glucagons levels appear to be excessive while in carnivores insulin levels may be deficient.
Dietary requirement	Method of expressing nutritional requirement based on the concentration of nutrient within the diet (% of the diet or g/kg diet)
Digestibility	A measure of diet quality based on the proportion of nutrients available for absorption.
Digestibility, Apparent	The relationship between nutrients consumed in the diet and nutrients that disappear from the gastrointestinal tract = (Nutrient intake – Nutrient in Feces)/Nutrient intake.
Digestibility, True	True digestibility corrected for the part of nutrients in feces of endogenous origin = (Nutrient intake - Nutrients in feces) + Endogenous fecal losses)/Nutrient intake.
Digestible energy (DE)	DE is the energy actually absorbed and digested = total energy minus energy lost in feces
Diglycerides	A lipid commonly used as an emulsifying agent.
Dipeptide	Two amino acids joined together by a peptide bond.
Direct calorimetry	Form of bomb calorimetry that measures metabolizable energy expenditure by the rate at which heat is released.
Disaccharide	Carbohydrate made of two monosaccharide units linked together (i.e. sucrose = glucose + fructose)
Docosahexanoic acid (DHA)	An eicosanoid and a member of the omega-3 fatty acid family.
“Dumping syndrome”	Cramping, diarrhea, and vomiting which may occur secondary to the introduction of excessive fluids into the intestines

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E

EFA	See Essential fatty acid
Egestion	A pellet containing indigestible materials (i.e. fur, bone, feathers) formed by gastric contractions in birds of prey. Antiperistaltic waves push the pellet up the esophagus and out of the mouth.
Egg	An excellent source of protein, vitamins, and minerals. Contains most essential amino acids. Contains B vitamins, vitamin D, and some vitamin E. Excellent source of iodine, zinc, and calcium. Of course even more calcium is present within the egg shell. Although iron is present in the egg, its bioavailability is unclear. The egg contains approximately 11.2% fat; the vast majority of which is found in the yolk.
Eicosanoids	Members of the omega-3 essential fatty acids family (i.e. eicosapentanoic acid, docosahexanoic acid) that reduce inflammation (perhaps by inhibiting the COX-2 enzyme) and are essential for brain development. Found in fatty fish such as salmon, white tuna, mackerel, rainbow trout, herring, halibut, and sardines.
Eicosapentanoic acid (EPA)	A member of the omega-3 fatty acid family which ideally should be included in the diet. See Eicosanoids.
Electrolytes	A substance that will dissolve into ions in solution such as sodium, potassium, chloride, calcium and phosphate.
Elemental diet	A nutritionally-balanced liquid diet that is in a highly digestible form so that it puts no stress on the gastrointestinal system.
Emulsifying agents	Food additive used to blend together ingredients like oil and water allowing greater contact between antioxidants and fats. Naturally-derived agents include lecithin, modified starches, monoglycerides, and diglycerides.
Energy	Not a nutrient, but one of the most critical components of the diet. Body obtains energy through oxidation of chemical bonds producing energy-rich compounds such as adenosine triphosphate (ATP).
Energy density	Number of calories provided in a given weight or volume of food expressed as kJ of diet/volume of diet or kcal/kg. Energy density is the primary factor that determines how much food is eaten daily
Energy, Gross	See Gross energy
Energy requirements	See Basal metabolic requirements (BMR) See Maintenance energy requirements (MER)
EPA	See Eicosapentanoic acid
Ergocalciferol	Also known as vitamin D2. Form of vitamin D used by mammals, but not used efficiently by birds
Ergosterol	Biologic precursor of vitamin D synthesized by plants, fungi, molds, lichens, and some invertebrates (i.e. snails, worms). Converted to vitamin D2 by ultraviolet light.
Esophagus	Muscular tube that extends from the oropharynx to proventriculus. The esophagus is relatively wider than in mammals and expandable due to a series of longitudinal folds. Mucus glands provide lubrication.
Esophagostomy tube	Feeding tube placed under general anesthesia for long-term feeding of the anorectic patient.
Essential fatty acids (EFAs)	Polyunsaturated fatty acids that cannot be assembled from other fats within the body, but must be consumed whole in food. Linoleic acid (omega-6) and linolenic acid (omega-3) are essential fatty acids in birds. The absolute requirement is much greater for linoleic acid than linolenic acid.
Ether extract	An estimate of fat content based on the portion of a compound soluble in ether.
Ethoxyquin	Synthetic antioxidant with high efficacy especially for oils containing high levels of polyunsaturated fatty acids. FDA Center for Veterinary Medicine requires that ethoxyquin must be declared on the label regardless of the source or amount. Although considered to be moderately toxic, ethoxyquin has been approved for use in animal feeds for more than 30 years.
Extruded diet	Mixture of ground grains and vitamin/minerals forced through an extruder under pressure and subjected to temperatures higher than for pellets (between 90-180°C). Manufacturers of extruded bird foods include Kaytee®, Zupreem®, and Mazuri®.
Extrusion	See Extruded diet
Exudativores	Birds that probe or drill for saps, gums, resins (i.e. sapsucker)

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F

Facultative frugivory	Many birds in temperate climates switch to a fruit-based diet during the fall.
Facultative insectivory	Many birds in temperate climates switch to an insect-based diet during the spring.
Faunivore	Species which consume foods almost exclusively of animal origin. Also known as a zoophage.
Fat	Complex molecule composed of fatty acids and glycerol which serves as a storage form of energy. Contains three times more energy than protein or carbohydrate. Each gram of fat supplies the body with about 9 calories Improves dietary palatability and texture which increases the danger of overeating and obesity.
Fat-soluble vitamins	See Vitamins, fat-soluble
Fatty acids	Building blocks of fats Chain of carbon atoms with hydrogen atoms attached and a carbon-oxygen-oxygen-hydrogen group at one end. Vary in carbon-chain length May be saturated, monounsaturated, or polyunsaturated Dietary fatty acid deficiencies impair wound healing and absorption of fat-soluble vitamins and may cause dry skin Manipulation of omega 3-to-omega 6 fatty acid ratio in diets can stimulate or reduce the immune response
Fatty acids, Essential	See Essential fatty acids
Fatty acids, short-chain (SCFA)	Volatile fatty acids produced by bacterial fermentation of fiber. Metabolism of fatty acids such as acetate, propionate, and butyrate provide energy to enterocytes and colonocytes.
Fatty liver and kidney syndrome	Syndrome seen in adult merlins and broiler chicks which may be caused by biotin deficiency
Feathers	Epidermal growths made of keratin, feathers make up the largest part of the protein mass of birds (5.7%) and 28% of total body protein. Amino acids found in feathers include proline, serine, glycine, cysteine, valine, and leucine and many non-essential amino acids.
Feeding trials	The most accurate method for determining metabolizable energy content of food. Requirements are determined by the Association of American Feed Control Officials.
Fermentation	Bacterial fermentation of fiber produces short-chain fatty acids and other end-products
Fiber	Group of complex carbohydrates with beta bonds that resist enzymatic digestion in most avian species but promote normal gastrointestinal motility. Bacterial fermentation of fiber provides energy. Examples of dietary fiber include cellulose, hemicellulose, pectin, plant gums, and mucilages.
Fiber, Insoluble	See Insoluble fiber
Fiber, Soluble	See Soluble fiber
First limiting amino acid	Amino acid in food that is most deficient relative to bird’s requirement
Fish	Nutritional value of fish varies with species, age, gender, stage of life cycle, season, location of catch, storage, and handling. However all fish are good sources of protein, and most fish are great sources of major and trace minerals. Some species contain very high levels of vitamins A and D. Although there are ample amounts of vitamin E in fresh fish, much of the vitamin E originally present may be destroyed prior to feeding since vitamin E is a natural antioxidant. Fatty fish such as salmon, white tuna, mackerel, rainbow trout, herring, halibut, and sardines are a rich source of omega-3 fatty acids. Unfortunately some types of fish may also contain environmental contaminants such as methylmercury or polychlorinated biphenols, particularly shark, swordfish, king mackerel, and tilefish
Flavonoids	See Bioflavonoids
Flax seed	Oil seed frequently fed to small granivores. A rich source of omega-3 polyunsaturated fatty acid.
Flax seed oil	A “heart-healthy” oil containing omega-6 and omega-3 fatty acids in a ratio off 2:1. Also known as linseed oil.
Florivore	Species that eat plant-based foods such as seeds, fruits, nuts, and berries. Also known as a phytophage.
Folates	See Folic acid
Folic acid	Group of B-vitamins (vitamins B10 and B11 and pteroylglutamic acid) with related activity. Folic acid plays a role in intermediary metabolism, particularly the synthesis of thymidine, a component of DNA. Folic acid and B12 work together to produce methionine from homocysteine, and folic acid is also involved in blood cell synthesis. Folic acid is synthesized by bacteria within the intestines; dietary sources include dark, leafy, greens, legumes, some fruits, organ meats, and egg yolks. Deficiency may lead to poor weight gain, anorexia, anorexia, leukopenia, glossitis, immunosuppression, poor feathering and pigmentation, reduced egg production, and reduced hatchability.
Folivore	Herbivore that mainly eats leaves (i.e. hoatzin)
Formulated diets	Commerical bird food products (i.e. pellets, extruded foods, whole grains and/or seeds mixed with pellets) are usually based on ground grains such as corn to supply energy and ground legumes such as soybean meal or peanut meal to supply protein.
Fortified	Something added to feed to increase its nutritional value. Many seed mixes are “fortified” by coating the seed with nutrients (i.e. spraying the shell). Since parrots and songbirds crack seeds before ingesting, waste occurs and very little nutrient is consumed.
Fructose	Monosaccharide also known as fruit sugar found in ripe fruits, honey, and some vegetables. Also formed from digestion or hydrolysis of the disaccharide, sucrose.
Frugivore	Concentrate selector that eat soft, moist fruits (i.e. macaws such as the green-wing macaw, orange-winged Amazon parrot, toucan, waxwing, and some pigeons. Many frugivores supplement their diet with insects.
Fungivore	Concentrate selector which eats fungus (i.e. Pygmy parrot)

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G

Gallbladder	Absent in some bird species (i.e. ostrich, hummingbird, passerines, and many species of pigeons, doves, and parrots) and present in other species such as ducks.
Gamma-tocopherol	Fraction of vitamin E with relatively low biological activity, but relatively high antioxidant activity
Garlic (Allium sativum)	A case report has suggested toxicity (nephrosis) after ingestion of large amounts of garlic. Garlic contains the toxic ingredient, thiosulphate.
Gastrin	Hormone which stimulates HCl secretion, and is also necessary for normal growth of the lining of the gut.
GE	See Gross energy
Gelatin	Colorless or pale yellow, clear, brittle protein derived from boiling specially prepared skin, bones, and connective tissue.
Generalist	Species which eat a variety of foods
Germination	See Sprouted seeds
Gizzard	See Ventriculus
Glucagon	Glucagon assists in keeping blood sugar in the normal range, and its action is opposite that of insulin. Glucagon forces many different body cells to release (or produce) glucose, with the end result of increasing blood sugar levels. Glucagon stimulates the liver to produce and release glucose into the bloodstream by stimulating hepatic glycogenolysis. Glucagon is usually secreted when the glucose levels drop in the bloodstream. For some reason, with avian diabetes
Gluconeogenesis	Metabolic pathway induced when glucose intake does not meet metabolic demands. Most birds shift to gluconeogenesis within several hours postprandial because of low levels of storage glycogen paired with a high metabolic rate. Primary substrates for gluconeogenesis are glycerol and amino acids.
Glucose	Glucose is the body’s basic source of energy. This monosaccharide is the main form in which carbohydrate is absorbed, exchanged between tissues, and channeled into metabolic pathways. A species’ ability to absorb glucose is generally equivalent to the amount of glucose in the diet (i.e. hummingbirds can absorb more glucose than chickens which can absorb more glucose than raptors).
Glutamate	Nonessential amino acid of birds
Glutamine	Nonessential amino acid of birds. Glutamine serves as the preferred source of energy and nitrogen for small intestinal mucosal cells.
Gluten	Plant proteins found in cereal grains like corn, barley, rye, and wheat. In mammals, maldigestive disease may be observed after some ingestion of some proteins (i.e. celiac disease).
Glycerin	See Glycerol
Glycerine	See Glycerol
Glycerol	A liquid sugar alcohol obtained from fats and oils; used as a humectant to keep foods soft and moist; sweet-tasting and low in toxicity
Glycine	An essential amino acid in growing chicks. A conditionally essential amino acid in chickens, and probably budgies, on diet low in methionine or argine, and probably in budgerigar parakeets. Can be converted to serine by a reversible reaction. Used to make pyrimidines and purines
Glycogen	Polysaccharide that the body can easily and rapidly convert to energy. Serves as the storage form of glucose in the liver and muscles.
GMO	See Non-GMO corn
Gnathotheca	The keratin layer covering the lower beak.
Goiter	Iodine deficiency seen mainly in budgerigar parakeets as a result of iodine-deficient water and millet-based seed mixtures. Clinical signs are secondary to enlargement of the thyroid gland and secondary compression of the trachea and/or crop. Treatment generally relies on iodine supplementation in drinking water.
Goitrogenic compounds	Foods that bind iodine making it unavailable for use such as peas, peanuts, soybeans, and flaxseed.
Golden conure	Species which requires relatively high dietary fat levels.
Gonys	Ventral midline curve of the lower beak.
Gout	Accumulation of uric acid tophi in or around joints or on serosal surfaces. Pathogenesis of gout is not completely understood but may be associated with conditions that reduce uric acid excretion or increase uric acid production such as dehydration, excess dietary calcium, and hypovitaminosis A. Although high dietary protein has been theorized, gout could not be induced in adult cockatiels fed up to 70% crude protein for 11 months, however sudden changes in dietary protein levels have also been suggested to lead to gout.
Graminivore	A species which feed on grasses (i.e. geese, swans)
Granivore	Species that eat grains, hard seeds, and hard, dry, nutrient-dense fruits (i.e. beans, nuts) such as the budgerigar parakeet, cockatiel, sparrow, and finch.
Grit	Grit is particulate matter needed for proper ventricular function in species that ingest seeds whole (i.e. pigeons, doves, struthioformes, free-ranging galliformes) to assist in grinding. Grit is not absolutely necessary in other seed-eaters, and if offered should only be given in small amounts. Grit should not be offered ad libitum since it may be associated with pica and secondary impaction.
Grit, Insoluble	Quartz or other forms of silica are examples soluble grit which does not act as a mineral source in birds.
Grit, Soluble	Small amounts of soluble grit may help birds meet their calcium needs. Examples include oyster shell, cuttlebone, limestone, canunda shell, and gypsum.
Gross energy (GE)	The total amount of potential energy within food. Also known as intake energy. Calculated with the use of a bomb calorimeter.
Growth	Requires greater amounts of protein, calcium, and energy, particularly in hatchlings
Guild	An assortment of species which use the same food resources. Guilds are classified by combining food type (i.e. granivore) with substrate (i.e. ground) and method for acquiring food (i.e. grazer)
Gum	Soluble fiber composed primarily of galacturonic acid.
Gypsum	Calcium sulfate provided as a soluble grit

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H

Hagen®	Manufacturer of a variety of extruded bird foods including Tropican™ parrot sticks.
Harrison’s Bird Foods®	Manufacturer of a family of certified organic formulated bird foods.
HDL	See High-density lipoproteins
Heat	Form of energy released in approximately 60% of metabolic reactions.
Heat increment	Losses in metabolizable energy due to intermediary metabolism (lowest for dietary lipid; highest for protein)
Hemicellulose	Insoluble and soluble fibers found in seed coverings (i.e. bran, whole grains)
Hemochromatosis	Massive accumulation of iron in the liver (iron storage disease) seen in captive toucans, mynahs, birds of paradise, starlings, and quetzals. Pathogenesis is unknown. A diet low in iron and vitamin C is advised.
Heptic lipidosis	Fatty liver disease is a reversible condition that may develop in birds fed high fat or high energy diets or with fatty acid or vitamin B deficiencies.
Herbivore	Browser that consumes leaves, buds, shoots, grasses (i.e. ostrich, grouse, some ducks)
High-density lipoproteins (HDL)	Group of lipoproteins that functions as a transporter of cholesterol in the blood. High levels reduce the risk of atherosclerosis and coronary heart disease.
High-quality proteins	See Protein, high-quality
Histidine	Essential amino acids in growing chickens used to make histamine
Homocysteine	Metabolic intermediary amino acid. Elevated blood levels increase the risk of heart disease by attacking cells lining the arteries.
Honey	Sweet, thick, sticky yellow or brown fluid produced by bees nutritionally similar to nectar
Honeydew	Secretions of sap-sucking insects such as the nymph stage of aphids, coccids, and plant lice (Pysllidae) nutritionally similar to nectar.
Horsemeat	Protein source used in commercially prepared Bird of Prey diets (i.e Nebraska Brand®)
Humectants	Glycerol and other sugars used to keep foods soft and moist.
Hyacinth macaw	Species with high dietary fat requirements
Hydroxylysine	Nonessential amino acid in birds
Hydroxyproline	Nonessential amino acid in birds

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I

Ideal protein	A protein that provides the exact balance of amino acids needed to meet the bird’s needs and provides enough nitrogen for synthesis of nonessential amino acids.
Incomplete protein	Protein source lacking sufficient amounts of all essential amino acids.
Indirect calorimetry	Form of bomb calorimetry that measures the rate of oxygen consumption and carbon dioxide release. This information can be used to calculate the rate of metabolizable energy expenditure.
Ingluvies	See Crop
Insectivore	A species that primarily eats insects (i.e. warbler, flycatcher, shrike)
Insoluble fiber	Fiber which passes through the gastrointestinal tract largely intake such as lignin, cellulose, and some hemicelluloses found in whole grains and other plants. Insoluble fiber absorbs water and promote gastrointestinal motility.
Insulin	A protein hormone made by the pancreas important in regulation of carbohydrate and lipid metabolism. Acts to decrease blood glucose by stimulating cellular uptake of cells, stimulating glycogen synthesis, and decreasing gluconeogenesis.
Iodine	Micromineral required for synthesis of thyroid hormones. Deficiency leads to goiter.
Iron	Most abundant trace element in the body present in enzymes and other proteins.
Iron storage disease	See Hemochromatosis
Isoleucine	An essential amino acid in birds
Isthmus	Area of constriction between the proventriculus and ventriculus present in granivorous species.

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J

Joule

SI unit for expressing energy (1 joule = 0.239 calories)

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K

Kaytee®	A producer of a variety of bird foods included Exact Rainbow™ pellets, Exact™ hand-feeding formula, as well as a line of organic products.
Kilocalorie (kcal)	Unit used to measure the amount of heat produced by metabolizing food. 1 kilocalorie is the energy needed to raise the temperature of 1kg of water by 1°C.
Koilin	Glycoprotein matrix or cuticle which protects the inner surface of the ventriculus or gizzard in granivorous species.

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L

L-carnitine	See Carnitine
Lactic acid	Acid produced by anaerobic fermentation of undigested dietary fiber within the large intestine.
Lactose	Disaccharide is the only carbohydrate of mammalian origin. It consists of a glucose and galactose molecule.
Lactose intolerance	Avian enterocytes lack the enzyme, lactase, and therefore lactose should be avoided whenever possible.
Lafeber Company®	Manufacturer of a variety of foraging diets such as Avi-Cakes™ and Nutri-Berries™, pellets, and the critical care formulas, Emeraid Psittacine™ and Emeraid Carnivore™.
Lamina muscularis	Middle (sometimes inner) layer of digestive epithelium
Lamina propria	Outermost layer of digestive epithelium
Lecithin	Phospholipids containing choline promote lipid transport in cell membranes. Used as an emulsifying agent.
Legumes	Family of plants rich in lysine such as soybeans, beans, and peas. Legumes also contain bioflavanoids and other polyphenols that act as antioxidants.
Lerp	Waxy substance secreted as a protective scale by psyllids (plant lice) that is nutritionally similar to nectar
Leucine	An essential amino acid in birds. High levels (such as those found in diets high in millet) interfere with the conversion of tryptophan to niacin.
Lignin	Insoluble fiber found in plant stems, leaves, and skin.
Limestone	A common dietary supplement (calcium carbonate) and a form of soluble grit. Crystalline limestone is called marble.
Limiting amino acid	The essential amino acid that is present in the smallest proportion. In bird food, this is most commonly methionine, tryptophan, or lysine.
Linoleic acid	Essential fatty acid for birds and a member of the omega-6 fatty acid family. Rich dietary sources include vegetables oils such as safflower oil, sunflower oil, corn oil, and soybean oil.
Linolenic acid	Essential fatty acid for birds and a member of the omega-3 fatty acid family. Commonly found in walnuts, flaxseeds or flaxseed oil, soybean or canola oil,.
Linseed oil	See Flax seed oil.
Lipid	Insoluble (hydrophobic) compounds such as fats (solid at room temperature) and oils (liquid at room temperature). Lipid is the primary energy source for birds between meals, throughout migration, and during embryonic development.
Lipoprotein	Protein paired with lipid that carries cholesterol through the body. Classified according to their densities as very low, low, and high-density lipoproteins.
Low-density lipoproteins (LDL)	Lipoproteins which transport cholesterol in the blood. High levels increase the risk of heart disease by promoting plaque formation and atherosclerosis.
Lutein	Dietary carotenoid
Lycopene	Dietary carotenoid
Lysine	An essential amino acid in birds and most labile of the amino acids. Deficiency results in bronze pigmentation of feathers in turkey poults

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M

Macaws	Some macaws require higher dietary fat levels. Some species may also be particularly susceptible to the toxic effects of vitamin D.
Macrofaunivore	Species that eat other vertebrates
Macrominerals	Minerals required in large quantities because they form a major part of the body’s structural components (i.e. calcium, phosphorus, magnesium)
Macromolecules	Large molecules which make up the majority of the diet (i.e. lipids, fiber, proteins, carbohydrates, and water)
Macronutrients	See Macromolecules
Magnesium	Macromineral found in some enzymes and used to make body tissues, especially bone. Dietary sources include bone, oil seeds, grains and fiber sources. Deficiencies may occur with intestinal or kidney disease or with drug use that that increases renal excretion of magnesium (i.e. diuretics, amingolycosides, amphotericin). Signs of deficiency may include weakness, ataxia, seizures, poor growth and lethargy in chicks, poor egg production, and poor hatchability in hens.
Maintenance energy requirements (MER)	Energy required to maintain body weight in a moderately active,healthy, non-reproducing adult in a thermoneutral environment. MER = Basal metabolic rate + energy required for supporting maintenance activities and thermoregulation. Daily energy requirements have been documented in budgies.
Malnutrition	See Refeeding Syndrome
Manganese	Trace element found in enzymes that metabolize carbohydrates and synthesize fats. Dietary sources include whole grains, fruits, and vegetables. Deficiency leads to reduced egg production and shell strength in laying hens, poor hatchability, and perosis in chicks and poults.
Manna	Fluid exuded from damaged plants which later crystallizes. Nutritionally similar to nectar.
Marble	Crystalline limestone
Mazuri®	A producer of a variety of zoological products including extruded bird foods.
ME	See Metabolizable energy
Mean retention time	The average length of time that food is retained in the gastrointestinal tract. Approximately 15-60 minutes in frugivores, 30 to 50 minutes in most avian nectarivores (80 minutes in rainbow lorikeets), and 40 to 100 minutes in granivores. Usually an order of magnitude shorter than the time required for complete evacuation of the gastrointestinal tract.
Meat byproducts	Tissues such as lung, spleen, kidney, brain, blood, bone, and intestine.
Meckel’s diverticulum	Yolk sac remnant located at the junction between the jejunum and ileum. Grossly visible in chickens, but only visible histologically in many species as a collection of lymphatic follicles. Also known as vitteline diverticulum.
Medium chain triglycerides	Triglycerides which serve as an excellent source of lipids and calories. May be a good substitute for fat since they are directly absorbed by the small intestine without a need for micelles or pancreatic secretion of lipase.
Menadione	The most common form of synthetic vitamin K (vitamin K3) which has vitamin activity 2 to 3 times higher than that of natural vitamin K1.
Menoquinone	Vitamin K2 synthesized by colonic bacteria.
Mercury	Common contaminant of some types of fish such as shark, swordfish, king mackerel, and tilefish
Metabolizable energy (ME)	The energy in food available to the body for use after losses from feces, urine, and the production of heat. Best determined by feeding trials, but ME may also be calculated using mathematical formulas. ME varies with the diet and the species. For instance, if a waterfowl and songbird are fed the same high-fiber diet, the waterfowl will have a higher ME due to its better ability to digest fiber.
Metabolizable energy coefficient (MEC)	Term often used to describe apparent metabolizable energy value. Expressed as a fraction of gross energy of the food (AME/GE)
Methionine	A sulfur-containing essential amino acid of used to make carnitine, creatine, niacin, polyamines, purines, and choline. Methionine may be broken down to make cysteine. Eggs are a rich source of methionine. Deficiency in the chick results in dark stress bars.
Microfaunivore	A species which eats invertebrates
Microminerals	A trace element required in small amounts such as iron and iodine.
Micronutrient	A substance, like a vitamin or mineral, needed in tiny amounts.
Microvilli	See villi
Migration	Period of high energy demands. Prior to migration, flight muscles hypertrophy and fat deposition occurs secondary to hyperphagia of high-energy foods (i.e fruits, seeds). Birds are the only vertebrates which fuel high-intensity exercise with fatty acids delivered from adipose tissue. Very-low-density lipoproteins transport fatty acids.
Milk thistle	See Silymarin
Millet	Non-oil seed frequently fed to small granivores that is low in protein and other essential nutrients. Diets high in millet should be supplemented with niacin.
Minerals	The inorganic portion of the diet (i.e. calcium, iron, magnesium, selenium, zinc). Meat-based foods are a better source of minerals than plant foods due to compounds such as phytates, oxalates, goitrogens, and fiber.
Mixed tocopherols	Naturally-derived antioxidant derived from distilling soybean oil residue. Further processing separates out the fractions: alpha (a), delta (d), and gamma (g). A mixture containing both alpha- and delta-tocopherols is the most effective natural antioxidant.
Modified Atwater factors	Values assigned for energy content of proteins and carbohydrates (3.5 kcal/g) and fats (8.5 kcal/g).
Molluscivore	A faunivore which primarily eats mollusks such as limpkins, snail kite, oystercatchers, and kiwi.
Molt	The process of shedding and replacing feathers associated with increased protein needs and increased energy needs due to the loss of insulation. See Feathers.
Molybdenum	Trace element which is part of several enzymes that metabolize proteins. Dietary sources include beans and grains. Molybdenum content in plants varies with soil levels.
Monoglycerides	A lipid commonly used as an emulsifying agents.
Monophagous	A species which eats only one kind of food (i.e. the Snail Kite primarily eats one species of freshwater snail).
Monosaccharides	A group of simple sugars (the simplest form of carbohydrate) such as glucose, fructose, or galactose. Monosaccharides can combine to form polymers. Simple sugars are required in large amounts for normal metabolism in hummingbirds, lories, and sunbirds. In most birds, simple sugars a great medium for overgrowth of yeast, and they should be avoided.
Monounsaturated fatty acids	Triglycerides with one double bond such as palmitoleic acid (i.e. olive oil).
Mycotoxins	Toxins produced by a fungus such as ochratoxin, oosporein, and aflatoxin.

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N

Nasofrontal hinge	Maxilla articulates with the skull at the nasofrontal hinge, an area of flexibility which allows a widening of oral opening in some birds such as parrots, flamingos, woodpeckers, and hornbills. The nasofrontal hinge is a synovial joint in parrots giving them the highest degree of flexibility and movement.
Nectar	Dilute sugar solution low in proteins, vitamins, and trace minerals. Predominant sugars include sucrose, glucose, and fructose.
Nectarivore	Feeding strategy practiced by lories, lorikeets, honeycreepers, hummingbirds, sunbirds, and honeyeaters which eat nectar, pollen, manna, honeydew, and/or lerp. Most species will also eat insects and/or mixtures of fruit.
Niacin	B vitamin created from tryptophan that plays an important role in cellular oxidation-reduction enzyme systems. Good dietary sources include animals, fish, cereals, legumes, and oil seeds. Deficiency may be associated with diets high in corn or millet. Niacin deficiency, also known as, pellagra or black tongue, leads to dermatitis, diarrhea, dementia, and death.
Nicotinamide	Metabolically active form of niacin.
Nitrogen	Element essential for the synthesis of nonessential amino acids
Nitrogen-corrected metabolizable energy (MEn)	Metabolizable energy values corrected for the loss or retention of body protein so that birds growing or losing weight are comparable.
Non-GMO corn	Any corn hybrid that has not been genetically modified through biotechnology procedures
Nutri-Berries	A Lafeber Company® product consisting whole grains and seeds mixed with pellets to create a balanced product.
Nutri-Meals	A Lafeber Company® product consisting of whole grains, fruits, vegetables, and seeds mixed with pellets to create a balanced product.
Nutrient deficiency	Addition of more nutrient improves growth, reproduction, fitness, or corrects some pathological condition.
Nutrient imbalance	High levels of one nutrient increase the requirement of another nutrient.
Nutrient toxicity	Nutrient levels are high enough to induce specific pathology.
Nutrient-dense	Fleshy fruit with large amounts of lipid and protein, but less water and sugar such as avocados, palms, dates
Nutrient density	Expression of nutrient content as grams per 100 kcal of metabolizable energy
Nutrient-dilute	Fleshy fruit with a relatively indigestible skin and a large proportion of seeds.
Nutrient requirement	See Dietary requirement
Nutrients	Components of the diet that provide energy and that have specific functions for growth, maintenance, and health. Divided into major categories: water, carbohydrates, proteins, fats, vitamins, and minerals.
Nutrients, essential	Nutrients that are not created by the body in quantities adequate to meet nutritional needs.
Nutrients, non-essential	Nutrients created by the body in quantities adequate to meet nutritional needs.
Nutritional niche	The exact foods consumed within a range of foods available.

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O

Oat groat	Hulled oat grain frequently added to seed mixtures for small granivores to increase protein level (range from 15-17.5% protein)
Obesity	A common problem in the pet bird. Species prone to obesity include galahs, budgerigars, sulfur-crested cockatoos, Amazon parrots, and cockatiels.
Obligate consumers	Species that consume a specific food item during their entire adult life.
Oil	Lipids that are liquid at room temperature.
Oligivore	Species which eats a limited number of foods, also known as a oligivore
Oligophage	See Oligivore
Oligosaccharide	Difficult to digest carbohydrates often found in plants made of 3 to 10 monosaccharide units. Provide nutrition for intestinal flora.
Omega-3 fatty acids	Family of polyunsaturated fatty acids which reduce platelet aggregation, decrease cholesterol and triglyceride levels, and lower blood pressure. Important omega-3 fatty acids include linolenic acid, eicosapentaenoic acid, and docosahexaenoic (DHA). Fish oils are a rich dietary source.
Omega-6 fatty acids	Unsaturated fatty acid, which along with omega 9 fatty acids, is more immunologically stimulating than omega 3 fatty acids. Linoleic acid is the shortest chain fatty acid and an essential fatty acid.
Omega-9 fatty acid	Unsaturated fatty acid, which along with omega 6 fatty acids, is more immunologically stimulating than omega 3 fatty acids. Not classififed as an essential fatty acid because it may be created from unsaturated fat.
Omega egg	Egg enriched with omega-3 fatty acids. Produced by hens fed a diet which includes flaxseed.
Omnivore	A generalist feeder that eats animal and plant matter. Also known as a polyphage or polyvore. Examples include the Sulphur-crested cockatoo, tinamous, bustards, quail, pheasants, cranes, and corvids.
Onion	Food item that should be avoided particularly if offered raw or in large amounts. Onions contain the toxic ingredient, thiosulphate. Dogs and cats with onion toxicity develop gastroenteritis and hemolytic anemia.
Optimal foraging theory	A concept that states a bird’s morphology, physiology, and behavior are shaped by evolutionary pressures to maximize its ability to acquire energy by foraging.
Organic	Foods made according to specific production standards such as absence of conventional pesticides or food additives. Manufacturers of organic bird foods include Harrison’s Bird Foods® and Kaytee®.
Oropharynx	The oral cavity and pharynx makes up one region in the bird because there is no soft palate, only a hard palate.
Oxalic acid	Compound found in plants that can form indigestible complexes with minerals such as calcium making them unavailable for absorption. Vegetables high in oxalic acid include amaranth, cassava, chives, parsley, purslane, and spinach.
Oyster shell	Source of dietary calcium. See Grit

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P

PABA	See Para-aminobenzoic acid
Pancreas	Glandular organ that secretes enzymes through three ducts which enter the duodenum. Enzymes hydrolyze most starches, proteins, and nucleic acids in foods. Alkaline fluid secreted makes chyme less acidic so that amylase may act.
Pantothenic acid	B-complex vitamin that serves as a component of acetyl coenzyme A (CoA) and the acyl-carrier protein. Found in most dietary food sources therefore deficiencies are rare. Signs of deficiency may include hepatic lipidosis, erratic appetites, weight loss, depressed growth, immunosuppression, ragged plumage, and dermatitis (rarely as severe as in biotin deficiency)
Papaverine	Alkaloid found in some plants.
Para-aminobenzoic acid (PABA)	PABA is an essential growth factor for microbes which is needed to make folic acid.
Parasympathetic	Nervous system that controls gastrointestinal motility
Parathyroid hormone (PTH)	Hormone which increases bone resorption to increase calcium levels.
Parenteral nutrition	Intravenous or intraosseous feeding with a modified nutritive solution directly absorbed by cells without first passing through the gastrointestinal tract.
Passerines	Species belonging to order Passeriformes with a basal metabolic rate that is usually higher when compared to non-passerines of similar size. BMR = 129 x body weight (kg)0.73
Peanuts	Oil seed highly susceptible to mycotoxins contamination due to growth conditions in the field.
Pectin	A soluble fiber found in fruits that helps to increase the viscosity of intestinal contents while increasing water-holding capacity. Composed of galactose, arabinose, and galacturonic aicd.
Pellagra	Niacin deficiency, See Niacin
Pellet	1). Formulated diet made by grinding a variety of grains, adding a vitamin-mineral premix, putting the mix through a hammer mill to ensure appropriate particle size, and using a dry or steam process under heat (70-80°C) to force it through a die to produce a pellet shape. 2). See Egestion
Pentose	A monosaccharide containing five carbon atoms which may be found in avian diets, especially those high in fiber (i.e. arabinose, xylose)
Pepsin	Enzyme that hydrolyzes protein at a variety of peptide bonds creating polypeptides. Secreted as an inactive precursor, pepsinogen.
Pepsinogen	Inactive precursor hydrolyzed by hydrochloric acid or previously activated pepsin to become an active enzyme.
Peptide	Short molecule created by amino acids joined together.
Perosis	See Chondrodystrophy
Persea spp.	See Avocado
Phenylalanine	An essential avian amino acid used to make melanin, epinephrine, norepinephrine, and thyroxine. Hydroxylation of phenylalanine creates tyrosine.
Phocacholic acid	See Beta-phocacholic acid
Phospholipids	Lipid molecule made with the mineral phosphorus that transports hormones and fat-soluble vitamins through blood and back and forth across cell membranes. Effectively lower serum cholesterol levels
Phosphorus	Macromineral found in bone and a structural component of RNA. High dietary levels are found in meat and eggs.
Phylloquinone	Vitamin K1 found in leafy, green plants.
Phytic acid	Phosphorus containing compound found in plants that can form indigestible complexes with minerals such as calcium making them unavailable for absorption.
Phytochemicals	Chemicals produced by plants which a variety of functions such as fibers, carotenoids, dithiolthiones, bioflavanoids, indole carbinols, isothiocyanates, mono- and triterpenoids, and thioallyl derivatives.
Phytophage	See Florivore
Pigeon’s milk	See Crop milk
Piscivore	Type of faunivore that eats fish
Planktonivore	A species that mainly eats zooplankton (also known as a planktivore)
Pollen	Fine to coarse powder consisting of pollen grains eaten by nectarivores along with nectar. Pollen contains highly digestible protein, a varied amino acid profile, as well as vitamins C and B-complex.
Polypeptide	A protein containing more than three peptides bonded together
Polyphage	See Omnivore
Polyphenol	Widespread, complex compounds in plants that contain phenol groups such as phenylpropanoids like lignins and bioflavonoids and tannins. Dietary sources include teas, berries, and walnuts.
Polysaccharides	Carbohydrates commonly found in plants consisting of thousands of monosaccharide units in plants such as cellulose, starch, and glycogen. Also known as complex carbohydrates
Polyunsaturated fatty acid (PUFAs)	A triglycerides which contain two or more double bonds. Essential fatty acids such as linoleic acid, linolenic acid, and arachidonic acid are PUFAs.
Polyvore	See Omnivore
Portomicron	Lipoproteins used to carry dietary triglycerides
Potassium	Principle intracellular cation
Potassium sorbate	Preservative used to prevent the formation of yeast and molds in food.
Precocial	Species that hatch with relatively well-developed eyes, muscles, coordination, and down feathers. The gastrointestinal tract is relatively immature at hatch, but food intake stimulates intestinal growth.
Preservatives	Substances added to food to protect nutrients (particularly dietary fats) from oxidative or microbial damage under normal use and storage conditions.
Preservatives, Naturally-derived	Generally not as efficacious as synthetic preservatives, but more expensive (i.e. mixed tocopherols, ascorbic acid, ascorbyl palmitate, and rosemary extract). Efficiency increases when naturally-derived antioxidants are combined.
Preservatives, Synthetic	Examples include butylated hydroxyanisole, butylated hydrostytoluene, tertiary butylhydroquine, and ethoxyquin.
Pretty Bird®	A producer of a variety of bird foods included pellets.
Probiotic	A preparation of live microbes; probiotics have been recommended for prevention and treatment of infectious diarrhea as well as prevention of antibiotic-induced diarrhea.
Proctodeum	Posterior or caudal-most region of cloaca. The bursa of Fabricious is found on the dorsal surface of the proctodeum.
Prokinesis	Flexion of the beak allowed by a nasofrontal hinge as seen in parrots, waterfowl, galliforms. Prokinesis also absorbs the shock associated with pecking, drilling, and seed cracking. Absent in some species like ostrich and raptors.
Proline	Essential amino acid in growing chickens
Propionate	Volatile or short-chain fatty acid produced by bacterial fermentation of fiber. Energy may be derived from its metabolism.
Propionic acid	See Propionate
Propylene glycol	Tasteless, odorless, colorless, clear, oily liquid added to food as a humectant since it easily absorbs moisture.
Protein	Large complex molecule made of hundreds to thousands of amino acids arranged as linear polymers. Protein is the body’s primary source of nitrogen.
Protein, High-quality	Highly digestible protein which contains all essential amino acids in their proportions which meet the animal’s needs. The higher the quality of protein, the lower the quantity needed to meet essential amino acid needs.
Protein degradation	Hydrolysis of protein that frees amino acids
Protein reserve	The portion of amino acids which may be mobilized from lean body tissues
Protein shift	The increase in protein requirements which occurs during egg production, often accompanied by a change in food preferences
Protein turnover	The process of continual synthesis and degradation of protein which leads to no net change in the amount of protein
Proventriculus	Glandular portion of the stomach that produces hydrochloric acid and pepsin to begin to break down and emulsify foods.
Proximate analysis	Laboratory analysis of foods to evaluate a limited number of parameters such as moisture content, crude protein, crude fat, mineral content, and fiber content.
Pteroglyglutamic acid	See Folic acid
PUFAs	See Polyunsaturated fatty acids
Pyloric stomach	Third, chamber-like pyloric region below the ventriculus present in many birds that eat fish, aquatic invertebrates, or aquatic plants.
Pyridoxal	One of the three compounds that make up vitamin B6, derived from animal tissue. See Pyridoxine.
Pyridoxamine	One of the three compounds that make up vitamin B6; derived from animal tissue. See Pyridoxine.
Pyridoxine	A plant-based compound that is part of vitamin B6. Vitamin B6 serves as a cofactor for enzymes involved in amino acid metabolism. Rich dietary sources include meats, grains, vegetables, and nuts. Deficiency leads to anorexia, reduced growth, muscle weakness, neurologic signs, and renal lesions, and neurologic signs.

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Q

Queen of Bavaria conures	See Golden conure
Quinones	The group of compounds that make up vitamin K.

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R

Rape seed oil	See Canola oil
Rectum	The short, small length of intestine between the ileocecal junction and cloaca. Also known as the colon or large intestine.
Refeeding syndrome	Electrolyte disturbance that may be seen with malnutrition, starvation, or prolonged diuresis. Reintroduction of nutrition leads to a rapid shift of ions from serum to the intracellular space depleting potassium, phosphorus, magnesium, or calcium stores. Avoid refeeding syndrome by introducing food cautiously, monitoring clinical status and electrolytes closely, and supplementing the diet as needed.
Reflux	See Contraction sequence
Renal disease	Nutritional causes of renal disease include excess dietary protein or calcium, hypovitaminosis A, and hypervitaminosis D.
Reproduction	Hens laying large clutches of eggs require large amounts of dietary protein and calcium.
Resting metabolic rate	The amount of energy used by a bird on a normal diet while resting quietly in a thermoneutral environment. Also known as the resting energy requirement, resting metabolic rate accounts for 60-75% of total daily intake.
Retention time	See Mean retention time
Retinal	Form of vitamin A with photoreceptive abilities in the rods due to the ability of the molecule to resonate between isomeric forms when struck by light photons.
Retinaldehyde	Retinal pigments formed by oxidation of vitamin A alcohols.
Retinene	See Retinaldehyde
Retinoic acid	Form of vitamin A which regulates hormonal actions
Retinoids	Group of natural and synthetic fat-soluble compounds collectively called vitamin A.
Retinol	An alcohol form of vitamin A and the primary form of vitamin A transferred to the egg
Retinyl-palmitate	Storage form of retinol found in the liver.
Retrograde flow	Normal reflux of digesta in the opposite direction. See Contraction sequence
Rhamphotheca	The outer horny or keratin layer of the entire beak.
Rhinotheca	The keratin layer covering the upper beak.
Rhynchokinesis	Beak articulation spread over a wide zone as opposed to a specific hinge. This is seen in members of order Charadriiformes such as plovers, sandpipers, avocets, and oystercatchers.
Riboflavin	Vitamin B2 serves as part of coenzymes in oxidation systems. Dietary sources include liver, leafy green plants, and fruits. Deficiency in growing poultry leads to retarded growth, diarrhea, leg paralysis (curled toe paralysis)
Rice flour	Flour relatively high in protein and gluten-free.
Rictus	Soft triangle of tissue found where the upper and lower beak meet (oral commissure).
Rosemary extract	Naturally-derived antioxidant extracted from dried rosemary shrub leaves(Rosemarius officinalis).
Roudybush®	Manufacturer of a variety of bird foods such as Careline™ pellets which includes diets marketed for intestinal, liver, and renal disease.

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S

Saccharose	See Sucrose
Safflower seeds	Bitter oil seeds which used to be considered superior to sunflower seeds because it was touted to be free of papaverine (however both sunflower and safflower seeds are free of papaverine).
Sanguinivore	Species that consumes blood; this is rare among birds (i.e. Sharp-beaked Ground Finch of the Galapagos islands)
Saturated fatty acids	Triglycerides containing no double bond between carbon atoms and which are therefore “saturated” with hydrogen atoms. In general, triglycerides in animal fats contain a higher percentage of saturated fatty acids than fats derived from plants. Saturated fatty acids, such as lauric acid, may be synthesized by the body and are therefore considered nonessential fatty acids.
Scenic Bird Food®	Producer of a variety of extruded bird food products including a line of hand weaning foods™.
SCFAs (Short-chain fatty acids)	See Fatty acids
Second limiting amino acid	Second most deficient amino acid in a given food
Secretin	Peptide hormone produced in the S cells of the duodenum in the crypts of Lieberkuhn which stimulates (1) the pancreas to secrete a digestive juice rich in bicarbonate, (2) the stomach to produce pepsin, and (3) stimulates the liver to produce bile.
Seeds	Most seeds commonly fed to pet birds are low in vitamin A, many B vitamins, calcium (<0.1% calcium), and other minerals. Grains such as millet, canary seeds, and corn are especially low with less than 0.03% calcium.
Seeds, Non-oil	Seeds that store most of their energy as starch and are relatively low in energy and protein (i.e. millet, canary seed, oat groats)
Seeds, Oil	Seeds that contain 50% fat or more and are therefore a rich source of energy, protein, omega-6 fatty acids, and vitamin E (i.e. safflower seeds, sunflower seeds, peanuts).
Selenium	Trace mineral used as a cofactor for the enzyme, glutathione perioxidase, in the antioxidant system. Since its functions are similar to vitamin E, selenium helps to spare vitamin E levels. Dietary sources include meat, seafood, and cereals.
Serine	Nonessential amino acid created from dietary glycine by a reversible reaction
Short-chain fatty acids	See Fatty acids
Silymarin	Antioxidant which may serve to protect hepatocytes; Also known as milk thistle.
Simple sugar	See Monosaccharide
Slipped Tendon	See Chondrodystrophy
Sodium	Principle extracellular cation. Frequently provided in minimal dietary levels to reduce moisture of feces. Dietary sources include fish, eggs, dried whey, poultry byproduct meal, and soy isolate.
Sodium benzoate	Preservative which serves as a mold inhibitor
Sodium sorbate	Preservative which serves as a mold inhibitor
Soluble fiber	Fermentable fiber sources such as pectin, gum, B-glucan, and some hemicelluloses which seem to lower blood cholesterol levels.
Soy protein	Protein source high in antioxidants derived from the soybean.
Soya bean	See Soybean
Soybean	Legume containing complete protein or sufficient amounts of essential amino acids (unlike other vegetables). Also a good source of dietary fiber. The first limiting amino acid is methionine.
Soybean meal	Created by extracting most of the oil from whole soybeans. Common protein source in modern grain-based diets fed to poultry and pet birds.
Specialist	Animal that eats a specific food type
Spirulina fusiformis	Blue-green algae which may be used as a source of vitamin A.
Sprouted seeds	Germination of seeds decreases phytate content (which may increase availability of calcium, magnesium, zinc, iron, and protein), but this also increases availability of phosphorus.
Starch	Polysaccharide of plants used for energy storage. Cereal grains such as corn, wheat, sorghum, barley, and rice are rich in starch.
Starvation	A condition resulting from serious or complete lack of nutrients. Starvation leads to shrinkage of vital organs, reduction in organ function, chronic diarrhea, anemia, loss of muscle mass, weakness, immunosuppression, and edema. Stress starvation can lead to glucose intolerance making protein and fat important energy sources. See Refeeding syndrome.
Stenophagous	Birds which consume a narrow range of food items (ex: vulturine parrot eats fruits from one or two figs in New Guinea)
Steroid alcohol	See Sterol
Sterol	Fat and alcohol compounds present in plant and animal tissues (i.e. ergosterol, cholesterol). Also known as steroid alcohols.
Sucrose	A disaccharide made of fructose and glucose also known as table sugar. Sucrose is the most common carbohyrate found in plants, and is also known as table sugar.
Sulfur amino acids	Methionine, cysteine, and cystine. Nestlings have substantial requirements for sulfur amino acids for plumage development, but marginal levels of cystine and methionine may be found in hand feeding formulas. Deficiencies may lead to abnormal or ragged plumage.
Summit metabolic rate	Maximal sustainable rate of heat production. This value (often 4 to 8-times basal metabolic rate) is an important determinant for the coldest temperature a bird can endure.
Sunflower seed	Oil seed that contains niacin, unlike most seeds. Although various cultivars have different fat levels, the darker the seed the more fat it contains.

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T

Tannins	Secondary plant compounds (polyphenols) used by plants to defend against herbivores. Interfere with protein digestion and can be toxic. Found in tea, bark of some trees, and the seeds and stems of grapes. Theorized to reduce iron absorption by acting as a natural chelator. Tea leaves must be added to diet with caution since they may reduce digestion and inhibit appetite.
Taste	Birds have a relatively small number of taste buds (i.e. 350 in parrot tongue, 9000 in human tongue), however taste is still an important factor in food acceptance and avoidance. Research in cockatiels found birds were insensitive to sugary flavors but very sensitive to potentially toxic compounds such as quinine, gramine, and tannins.
Taurine	A nonessential amino-sulfonic acid in birds that may be synthesized from methionine and cysteine.
Tertiary butylhydroquine (TBHQ)	Highly effective synthetic antioxidant approved for use in the United States, but not in Canada, Japan, or the European Union.
Thiamin	Vitamin B1 is taken up by all cells of the body and serves as a conenzyme for several enzymes. Rich dietary sources include microbes (yeast, zooplankton), animal origin, egg yolk, some cereal grains, and dried Brewer’s yeast. Supplementation is indicated when feeding thawed frozen fish. Deficiency results in central nervous system signs. Requirements of pet birds have been reported to be higher than in poultry (0.01-0.04 mg/day in canary and parrot 2-5 mg/kg feed in parrots)
Thiaminase	Enzyme found in high levels in some species of raw fish such as herring, smelt, mackerel, carp, shellfish (i.e. clams), as well as some bacteria (i.e. Clostrridium sporogenes), yeast, and fungi. Thiaminases are destroyed by cooking. Recommended supplementation for piscivores fed frozen fish is 25-30 mg /kg of fish (wet basis).
Thiamine	See Thiamin
Thiosulfite	Toxic compound found in onion and to a lesser extend garlic
Threonine	An essential amino acid in the bird
TME	See True metabolizable energy
Tocopherols	A component of vitamin E. Alpha tocopherols are the most active form of vitamin E in the body, and the component most commonly found in pet foods. Delta tocopherols are the most potent antioxidant for foods, but the least biologically active form.
Tocotrienols	A component of vitamin E
Tomia	Cutting edges of the beak
Tongue	Moved by hyoid apparatus in most birds. Parrots possess intrinsic tongue muscles.
Torpor	Technique of small birds in cool climates (i.e hummingbirds) who reduce overnight energy requirements by decreasing body temp to less than 77°F (25°C)
Total daily requirement	Maintenance requirement plus additional metabolizable energy needs for depositing tissues associated with growth, reproduction, molt, and reserves needed for migration or seasonal deprivation.
Total energy requirement	A combination of all requirements for life and its stages including growth, reproduction, and molt.
Triglyceride	A simple lipid made of three fatty acids linked to one molecule of glycerol. The most important form of dietary fat and the densest storage form of energy. Triglycerides are stored in adipose tissue in the adult and in yolk in the embryo. Triglycerides facilitate absorption of fat-soluble vitamins and increase palatability of foods in some species.
Tripeptide	Three peptides bonded together
True metabolizable energy (TME)	Correction of apparent metabolizable energy for the portion of excreta that has nothing to do with consumption of food
Tryptophan	An essential avian amino acid which is used to make serotonin and melatonin
Tyrosine	A nonessential amino acid created by hydroxylation of phenylalanine

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U

Urate	Salt of uric acid
Uric acid	Nitrogenous end product of protein and purine metabolism in birds synthesized in the liver, and to a lesser extent, the kidney.
Urodeum	The middle component of the cloaca that receives the ureters and reproductive tract.
Urolithiasis	Formation of urate concretions in the ureters which has been linked with excess dietary calcium, dietary electrolyte imbalances, and infectious bronchitis virus infection in chickens.

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V

Valine	An essential avian amino acid
Vent	The external opening to the cloaca; often appears as a transverse slit.
Ventriculus	The large, muscular component of the stomach with a thick inner cuticle or koilin in granivores and insectivores. Nectarivores tend to have small, less muscular gizzards.
Very-low-density lipoproteins (VLDL)	A lipoprotein that carries dietary fatty acids. A yolk-targeted VLDL is made by the liver, which targets the ovary in hens. In humans, VLDL may increase the risk of atherosclerosis by carrying cholesterol to tissues.
Villi	Microvilli increase the surface area of the intestine for nutritional absorption. Some frugivorous and nectarivorous species have exceptionally long intestinal microvilli (> 7 µm) which are thought to aid in absorption of sugars. Villi extend into the rectum and coprodeum of budgerigars.
Viscosity	Fiber increases viscosity of intestinal contents. As visciosity increases, diffusion of substrates and digestive enzymes decreases.
Vitamin	An organic, dietary component essential in minute quantities. A lack in the diet leads to deficiency, however requirements vary with the life stage. Growing and reproducing animals have higher requirements.
Vitamin A	Group of fat-soluble compounds called retinoids. Vitamin A is essential for vision (especially night vision), immune response, epithelial cell growth and repair, bone growth, reproduction, embryonic development, and epithelial integrity of respiratory, urinary, and intestinal tracts. Highest levels are found in liver, fish liver oils, egg yolk. Deficiency can lead to squamous metaplasia of mucous membranes, salivary glands, ureteral mucosa and collecting ducts; neurologic signs, decreased egg production, poorly formed shells, early embryonic death, and decreased sperm production. Research shows that adult cockatiels at maintenance are more susceptible to toxicity than deficiency. Toxicity can result in skeletal malformation, spontaneous fractures, prolonged clotting times and internal hemorrhage, anorexia, slow growth, weight loss, skin thickening, enteritis, conjunctivitis, hepatic lipidosis, and reduced function of the liver and kidneys.
Vitamin B-complex	Group of water-soluble vitamins with similar metabolic functions: biotin, cobalamin (B12), choline, folic acid (B10, B11), niacin, pantothenic acid, pyridoxine (B6), riboflavin (B2), thiamin (B1)
Vitamin B1	See Thiamin
Vitamin B2	See Riboflavin
Vitamin B6	See Pyridoxine
Vitamin B10	See Folic acid
Vitamin B11	See Folic acid
Vitamin B12	See Cobalamin
Vitamin C	L-ascorbic acid is a water-soluble vitamin made from glucose within the liver and/or kidney of most birds except for many passerines and some galliforms such as the willow ptarmigan. Vitamin C serves as an antioxidant and free radical scavenger, plays a role in collagen synthesis, immune function (at large doses), and it is also involved in drug, steroid, and tyrosol metabolism. Vitamin C increases absorption of iron. Signs of deficiency have not been documented in pet birds.
Vitamin D	Group of fat-soluble sterols such as cholecalciferol (D3) and ergosterol (D2) that regulate calcium and phosphorus absorption, mobilization, and deposition in bone and intestines. Vitamin D3 is stored in liver, muscle, and fat tissue. Deficiency can lead to rickets in young animals and osteomalacia and osteoporosis in adults. Toxicity can result in hypercalcemia and soft tissue mineralization, particularly in nestling parrots. Macaws may be predisposed to hypervitaminosis D.
Vitamin E	Fat-soluble vitamin, consisting of tocopherols and tocotrienols, which serves as a natural antioxidant. Tocopherol levels are highest in green leaves. Other dietary sources include vegetable oils, seeds, and cereal grains. Animal tissues tend to be low in vitamin E, although highest levels are found within the liver and fat. Vitamin E must be carefully maintained in formulated diets. Signs of deficiency include muscular dystrophy of the heart or ventriculus, steatitis, encephalomalacia, exudative diathesis and testicular degeneration. Vitamin E is one of the least toxic vitamins, however extremely high doses may lead to impaired bone mineralization, reduced hepatic storage of vitamin A, and coagulopathies.
Vitamin K	Group of fat-soluble vitamins called quinones required for synthesis of clotting factors II, VII, IX, and X. Dietary sources include green leafy vegetables, cabbage, cauliflower, liver, egg, alfalfa meal, oil seed meal, and certain fish meals. Animal sources are generally lower in vitamin K when compared to plant sources. Vitamin K1 is phylloquinone. Vitamin K2 , menoquinone, is synthesized by bacteria in the large intestine. Vitamin K3 (menadione) is the most common form of synthetic vitamin K. Certain drugs, mainly antibiotics, decrease intestinal absorption of vitamin K. Deficiency may also occur with intestinal malabsorption or ingestion of anticoagulants. Conures may have higher requirement for vitamin K.
Vitamins, fat-soluble	Vitamins passively absorbed and transported with chylomicrons to the liver. Vitamins A, D, E, and K
Vitamins, water-soluble	Vitamins absorbed by active transport (vitamins C and B-complex)
Vitelline diverticulum	See Meckel’s diverticulum
Vitellogenin	Protein synthesized by the liver of the laying hen that complexes with phospholipids and cholesterol
VLDL	See Very-low-density lipoproteins
Volatile fatty acids	Short-chain fatty acids: acetic, propionic, and butyric acids which provide energy when metabolized.

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W

Water	The most critical part of the diet related to survivability. Of bird species studied, canaries are most sensitive to water deprivation, particularly during the first few weeks of life.
Water-soluble vitamins	See Vitamins, water-soluble
Weaning	Gradual process of transition to a solid food diet that occurs in response to physiologic changes of growth.
Wood sugar	See Xylose

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X

Xanthophyll	A type of carotenoid pigment (i.e. lutein, zeaxanthin) and a natural antioxidant
Xerophilic species	Able to go for months w/o drinking water Budgerigar parakeets, Zebra finches
Xylose	Monosaccharide containing five carbon atoms or pentose also known as wood sugar.

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Y

Yolk

Yellow spherical portion of the egg that provides nutrition to the developing embryo. Yolk gets its color from carotenoids. Yolk lipids (vitellogenins and lipoproteins) are made by the liver in response to rising estrogen levels, and transported to ovarian follicles in the blood. (During this time, the liver increases in size and appears bright yellow in color).

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Z

Zeaxanthin	Dietary carotenoid that gives egg yolk, corn, saffron, and many other plants their characteristic color.
Zinc	Trace element with a wide variety of roles. Important for carbohydrate, lipid, protein, and nucleic acid metabolism; protects nerve and brain tissue, protects against free radicals, and boosts immunity. Dietary sources include meat and fiber. Zinc can decrease the body’s ability to utilize copper.
Zone of thermoneutrality	Range of environmental temperatures at which an adult bird can maintain body temperature without influencing maintenance energy requirements
Zoophage	A life form that eats animal material, also known as a faunivore
Zupreem®	Manufacturer of a variety of bird food products including a line of colorful extruded bird foods (FruitBlend™) and dye-free extruded foods (Natural™)

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References

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Bernard JB, Allen ME. Feeding captive piscivoroous animals: nutritional aspects of fish as food. Nutritional Advisory Group. Published September 1997, modified March 2002. Accessed on June 23, 2007 at http://www.nagonline.net/Technical%20Papers/
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Committee on Animal Nutrition. The Role of Chromium in Animal Nutrition. Washington D.C., National Academies Press. 1997. pp. 53-62

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USDA Nutrient Data Laboratory. Oxalic acid content of selected vegetables. Accessed on June 23, 2007 at http://www.nal.usda.gov/fnic/foodcomp/Data/Other/oxalic.html.

Vink-Nooteboom M, Lumeij JT, Wolvekamp WTC. Radiography and image-intensified fluoroscopy of barium passage through the gastrointestinal tract in six healthy Amazon parrots (Amazona aestiva). Vet Radiol Ultrasound 44 (1):43–48, 2003.

Wade LL, Newman SJ. Hemoglobinuric nephrosis and hepatosplenic erythrophagocytosis in a Dusky-headed conure after ingestion of garlic. J Avian Med Surg 18(3):155-161, 2004.

Wolf P, Kamphues J. Hand rearing of pet birds—feeds, techniques, and recommendations. J Anim Physiol Anim Nutr 87(3-4):122-128, 2003.

Wortinger A. Nutrition for Veterinary Technicians and Nurses. Blackwell Publishing, Oxford, UK, 2007.