Avian Nutrition Glossary

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AAFCOSee the Association of American Feed Control Officials
AcetatePrimary volatile or short-chain fatty acid produced during bacterial fermentation of fiber. Energy may be derived from its metabolism.
Acetic acidSee Acetate
AflatoxinMycotoxins produced by Aspergillus flavus or A. parasiticus growing on corn, peanuts, or cottonseed.
African grey
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 wingSee Angel wing
amino acid
AlbuminGlobular proteins found in egg white and blood plasma.
Digestion using microbial assistance such as digestion of plant fiber
Allocholic acidMajor bile acid of faunivores
Alpha-caroteneDietary carotenoid
Alpha-tocopherolMost biologically active form of vitamin E with relatively little antioxidant efficacy.
AltricialSpecies that hatch with closed eyes, little down, and poor musculature. Require extensive parental assistance and grow very quickly post-hatch.
Amino acidMolecule 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
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 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-essentialAmino acids that can be synthesized from nitrogen (alanine, asparagine, cysteine, glutamine, serine, and tyrosine.
AmmoniaCompound excreted by chickens on very high protein diets in addition to uric acid.
AmylaseAn enzyme that 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.
AmylopectinA component of starch.
AmyloseA component of starch.
Angel wingA 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.
AntioxidantAny substance that helps preserve food by retarding deterioration, rancidity, or discoloration caused by oxidation.
Energy values of a bird food may be expressed as:nutrient intake – nutrient in droppings)/nutrient intake
Apparent metabolizable
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.
ArabinoseA monosaccharide containing five carbon atoms or pentose.
Arachidonic acidA 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.
ArginineEssential amino acid of birds used to create creatine and polyamines. Deficiency causes an upward curling of the remiges (wing feathers) in chicks.
Ascorbic acidSee Vitamin C
Fat-soluble form of vitamin C used as a natural antioxidant.
AsparagineNonessential amino acid of birds
AspartateNonessential amino acid of birds
Association of
American Feed Control Officials (AAFCO)
Government organization that oversees pet food production
AstaxanthinDietary carotenoid pigment found in microalgae, krill, and shrimp. This pigment is used naturally and commercially in flamingos to provide color.
Atwater factorsSee modified Atwater factors
Avi-CakesLafeber Company product containing whole grains and seeds mixed with a pellet to create a balanced product.
AvidinCompound in raw egg white which binds biotin making it unavailable for absorption. Cooking destroys avidin.
Avocado (Persea
Food item to avoid in birds including the leaves. Some species may be toxic causing cardiomyopathy and death. Pathogenesis is unclear.


B6See Pyridoxine
B12See Cobalamin
BalancedLabel 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
Nutrients needed to maintain basic life functions (replaces losses inherent in being alive)
BCAASee Branched chain amino acids
BCSSee Body condition score
BeakSee Bill
Beta-caroteneDietary 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-cryptoxaninDietary carotenoid
Beta-glucanDietary fiber found in oats and barley.
Major component of bile in ducks, geese, and flamingos
BHASee Butylated hydroxyanisole
BHTSee Butylated hydroxytoluene
BileGreen liquid made in the liver that enables fats to mix with water.
Bile acidsSteroid 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 ductsCarry 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 saltsDetergent-like compounds that help to emulsify fatty foods for proper digestion and absorption.
BillExternal anatomic structure of birds used for eating, grooming, manipulating objects, probing for food, and feeding young. Also known as the beak or rostrum.
BioavailabilityDescribes 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.
BioflavonoidsA 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 valueThe 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.
BiotinSulfur-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 tongueSee Pellagra
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 calorimetryCalorimeter 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 mealA 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
BulkFeature of plant material related to its ability to hold water. Bulk shortens transit time and can decrease nutrient digestibility.
hydroxyanisole (BHA)
Synthetic antioxidant with relatively high efficacy.
hydroxytoluene (BHT)
Synthetic antioxidant with relatively high efficacy.
ButyrateVolatile or short-chain fatty acid produced by bacterial fermentation of fiber. Energy may be derived from its metabolism.
Butyric acidSee Butyrate


CalciferolSee Cholecalciferol
CalciumThe 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 chlorideTexturizer added to canned foods to keep them from turning mushy.
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.
Preservative which serves as a mold inhibitor.
CalorieThe term commonly substituted for kilocalorie.
Canary seedNon-oil seed frequently fed to small granivores to increase the protein in a seed mixture.
Cane molassesThe 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 oilA “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.
CanthaxanthinDietary carotenoid pigment found in green algae, fish, and crustacea. Used naturally and commercially in flamingos and other pink or red birds to provide color.
CarbohydrateA 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.
CarnivoreType of faunivore that consumes terrestrial vertebrates.
CarnitineL-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.
CaroteneSee Beta-carotene
CarotenoidsGroup 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-throughA 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.
CaseinProtein found in dairy products such as milk and cheese; also used as a binding agent in many food items
CCKSee Cholecystokinin
CecaA 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.
CecotropesNutrient-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.
CecotrophyIngestion of cecotropes practiced by some birds.
CecumSee Ceca
Celiac diseaseA 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.
CellulosePolysaccharide 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 scoreIndex 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.
Major bile acid of many wild birds
ChitinMucopolysaccharide within the exoskeleton of many invertebrates.
Choanal slitMedian slit in hard palate of birds which connects the oropharynx and the nasal cavity.
CholecalciferolForm 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.
A peptide hormone of the gastrointestinal tract responsible for stimulating the digestion of fat and protein.
CholesterolA 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 acidMajor bile acid of faunivores.
CholineB-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.
ChondrodystrophyCondition 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.
ChloridePrinciple extracellular anion.
CHOAbbreviation for carbohydrate based on the fact that compounds are made primarily from carbon atoms and water.
ChromiumTrace 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.
ChylomicronFat 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.
ChymePartially digested liquid that exits the stomach.
Citric acidNatural antioxidant found in citrus fruits often used in combination with other naturally-derived antioxidants.
CloacaCommon chamber and outlet which receives the gastrointestinal, urinary, and reproductive tracts.
CobalaminVitamin 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
CobaltTrace element found in cobalamin or vitamin B12
CollagenFibrous proteins present in connective tissue; converted to gelatin with prolonged boiling.
Colonsee Rectum
ComplementarityThe 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).
CompleteTerm 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 proteinProtein source that contains ample amounts of all essential amino acids.
See Polysaccharides
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.
Small birds in cool climates may decrease their energy needs overnight by reducing body temperature between 25 to 35°C. See torpor.
CopperTrace 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.
CoprodeumAnterior component of the cloaca that receives the gastrointestinal tract.
CoprophagyIngestion of rectal or cecal feces.
CornGrain 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.
CropDiverticulum or widening of the esophagus lined with thick, cornified epithelium. Mucus gland secretions soften food.
Crop milkA 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.
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 fiberOld-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.
CrustacivoreSpecies which feed on large numbers of crustaceans (i.e. crab plover, some rails, penguins, auks)
CulmenDorsal midline of the upper beak.
Curly toe
Flexion of digits with toes curled under which may occur in chicks with riboflavin deficiency.
CuticleGlycoprotein matrix that protects the inner surface of the ventriculus.
CuttleboneSource of dietary calcium
Cuttlefish boneSee Cuttlebone
CyanideChemical compound present in apple seeds as well as cherry, plum, apricot, and peach pits.
CyanocobalaminSee Cobalamin
CysteineNonessential amino acid of birds created by degradation of methionine. Feathers and eggs are rich in cysteine.


DabblerTechnique 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)
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 requirementMethod of expressing dietary requirement based on intake (mg/day or mg/kg BW/day)
DESee Digestible energy
7-dehydroxycholesterolCholesterol 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-tocopherolsFraction of vitamin E with low biologic activity but relatively high anti-oxidant efficacy.
DHASee Docosahexanoic acid
Diabetes mellitusAn 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.
Method of expressing nutritional requirement based on the concentration of nutrient within the diet (% of the diet or g/kg diet)
DigestibilityA measure of diet quality based on the proportion of nutrients available for absorption.
The relationship between nutrients consumed in the diet and nutrients that disappear from the
gastrointestinal tract = (Nutrient intake – Nutrient in Feces)/Nutrient intake.
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 is the energy actually absorbed and digested = total energy minus energy lost in feces
DiglyceridesA lipid commonly used as an emulsifying agent.
DipeptideTwo amino acids joined together by a peptide bond.
Form of bomb calorimetry that measures metabolizable energy expenditure by the rate at
which heat is released.
DisaccharideCarbohydrate made of two monosaccharide units linked together (i.e. sucrose = glucose +
acid (DHA)
An eicosanoid and a member of the omega-3 fatty acid family.
Cramping, diarrhea, and vomiting which may occur secondary to the introduction of excessive fluids into the


EFASee Essential
fatty acid
EgestionA 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.
EggAn 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.
EicosanoidsMembers 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.
acid (EPA)
A member of the omega-3 fatty acid family which ideally should be included in the diet. See Eicosanoids.
ElectrolytesA substance that will dissolve into ions in solution such as sodium, potassium, chloride, calcium and phosphate.
Elemental dietA
nutritionally-balanced liquid diet that is in a highly digestible form so
that it puts minimal stress on the gastrointestinal system.
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.
EnergyNot 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 densityNumber 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, GrossSee Gross energy
See Basal metabolic requirements (BMR)
See Maintenance energy requirements (MER)
EPASee Eicosapentanoic acid
ErgocalciferolAlso known as vitamin D2. Form of vitamin D used by mammals, but not used efficiently by birds
ErgosterolBiologic precursor of vitamin D synthesized by plants, fungi, molds, lichens, and some invertebrates (e.g. snails, worms). Converted to vitamin D2 by ultraviolet light.
EsophagusMuscular 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.
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 extractAn estimate of fat content based on the portion of a compound soluble in ether.
EthoxyquinSynthetic 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 dietMixture 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®.
ExtrusionSee Extruded diet
ExudativoresBirds that probe or drill for saps, gums, resins (i.e. sapsucker)


Many birds in temperate climates switch to a fruit-based diet during the fall.
Many birds in temperate climates switch to an insect-based diet during the spring.
FaunivoreSpecies which consume foods almost exclusively of animal origin. Also known as a zoophage.
FatComplex 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.
See Vitamins, fat-soluble
Fatty acidsBuilding 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,
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
FeathersEpidermal 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 trialsThe most accurate method for determining metabolizable energy content of food. Requirements are determined by the Association of American Feed Control Officials.
FermentationBacterial fermentation of fiber produces short-chain fatty acids and other end-products
FiberGroup 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, InsolubleSee Insoluble fiber
Fiber, SolubleSee Soluble fiber
First limiting
amino acid
Amino acid in food that is most deficient relative to bird’s requirement
FishNutritional 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
FlavonoidsSee Bioflavonoids
Flax seedOil seed frequently fed to small granivores. A rich source of omega-3 polyunsaturated fatty acid.
Flax seed oilA “heart-healthy” oil containing omega-6 and omega-3 fatty acids in a ratio off 2:1. Also known as linseed oil.
FlorivoreSpecies that eat plant-based foods such as seeds, fruits, nuts, and berries. Also known as a phytophage.
FolatesSee Folic acid
Folic acidGroup 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
FolivoreHerbivore that mainly eats leaves (i.e. hoatzin)
Formulated dietsCommerical 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.
FortifiedSomething 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.
FructoseMonosaccharide also known as fruit sugar found in ripe fruits, honey, and some vegetables. Also formed from digestion or hydrolysis of the disaccharide, sucrose.
FrugivoreConcentrate selector that eat soft, moist fruits (e.g. macaws such as
the green-wing macaw, orange-winged Amazon parrot, toucan, waxwing, and some
pigeons. Many frugivores supplement their diet with insects.
FungivoreConcentrate selector which eats fungus (i.e. Pygmy parrot)


GallbladderAbsent 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-tocopherolFraction of vitamin E with relatively low biological activity, but relatively high antioxidant activity
Garlic (Allium
A case report has suggested toxicity (nephrosis) after ingestion of large amounts of garlic. Garlic contains the toxic ingredient, thiosulphate.
GastrinHormone which stimulates HCl secretion, and is also necessary for normal growth of the lining of the gut.
GESee Gross energy
GelatinColorless or pale yellow, clear, brittle protein derived from boiling specially prepared skin, bones, and connective tissue.
GeneralistSpecies which eat a variety of foods
GerminationSee Sprouted seeds
GizzardSee Ventriculus
GlucagonGlucagon 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
GluconeogenesisMetabolic 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.
GlucoseGlucose 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).
GlutamateNonessential amino acid of birds
GlutamineNonessential amino acid of birds. Glutamine serves as the preferred source of energy and nitrogen for small intestinal
mucosal cells.
GlutenPlant proteins found in cereal grains like corn, barley, rye, and wheat. In mammals, maldigestive disease may be observed after some ingestion of some proteins (e.g. celiac disease).
GlycerinSee Glycerol
GlycerineSee Glycerol
GlycerolA liquid sugar alcohol obtained from fats and oils; used as a humectant to keep foods soft and moist; sweet-tasting and low in toxicity
GlycineAn 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
GlycogenPolysaccharide that the body can easily and rapidly convert to energy. Serves as the storage form of glucose in the liver and muscles.
GMOSee Non-GMO corn
GnathothecaThe keratin layer covering the lower beak.
GoiterIodine 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.
Foods that bind iodine making it unavailable for use such as peas, peanuts, soybeans, and flaxseed.
Golden conureSpecies which requires relatively high dietary fat levels.
GonysVentral midline curve of the lower beak.
GoutAccumulation 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.
GraminivoreA species which feed on grasses (e.g. geese, swans)
GranivoreSpecies that eat grains, hard seeds, and hard, dry, nutrient-dense fruits (i.e. beans, nuts) such as the budgerigar parakeet, cockatiel, sparrow, and finch.
GritGrit 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, InsolubleQuartz or other forms of silica are examples soluble grit which does not act as a mineral source in birds.
Grit, SolubleSmall 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.
GrowthRequires greater amounts of protein, calcium, and energy, particularly in hatchlings
GuildAn assortment of species which use the same food resources. Guilds are classified by combining food type (e.g. granivore) with substrate (e.g. ground) and method for acquiringfood (e.g. grazer)
GumSoluble fiber composed primarily of galacturonic acid.
GypsumCalcium sulfate provided as a soluble grit


Hagen®Manufacturer of a variety of extruded bird foods including Tropican™ parrot sticks.
Harrison’s Bird
Manufacturer of a family of certified organic formulated bird foods.
HDLSee High-density lipoproteins
HeatForm of energy released in approximately 60% of metabolic reactions.
Heat incrementLosses in metabolizable energy due to intermediary metabolism (lowest for dietary lipid; highest for protein)
HemicelluloseInsoluble and soluble fibers found in seed coverings (i.e. bran, whole grains)
HemochromatosisMassive 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 lipidosisFatty 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.
HerbivoreBrowser that consumes leaves, buds, shoots, grasses (i.e. ostrich, grouse, some ducks)
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.
See Protein, high-quality
HistidineEssential amino
acids in growing chickens used to make histamine
HomocysteineMetabolic intermediary amino acid. Elevated blood levels increase the risk of heart disease by attacking cells lining the arteries.
HoneySweet, thick, sticky yellow or brown fluid produced by bees nutritionally similar to nectar
HoneydewSecretions of
sap-sucking insects such as the nymph stage of aphids, coccids, and plant
lice (Pysllidae) nutritionally similar to nectar.
HorsemeatProtein source used in commercially prepared Bird of Prey diets (e.g Nebraska Brand®)
HumectantsGlycerol and other sugars used to keep foods soft and moist.
Hyacinth macawSpecies with high dietary fat requirements
HydroxylysineNonessential amino acid in birds
HydroxyprolineNonessential amino acid in birds


Ideal proteinA 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.
Protein source lacking sufficient amounts of all essential amino acids.
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.
IngluviesSee Crop
InsectivoreA species that primarily eats insects (i.e. warbler, flycatcher, shrike)
Insoluble fiberFiber 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.
InsulinA 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.
IodineMicromineral required for synthesis of thyroid hormones. Deficiency leads to goiter.
IronMost abundant trace element in the body present in enzymes and other proteins.
Iron storage
See Hemochromatosis
IsoleucineAn essential
amino acid in birds
IsthmusArea of constriction between the proventriculus and ventriculus present in granivorous species.


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


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.
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.
KoilinGlycoprotein matrix or cuticle which protects the inner surface of the ventriculus or gizzard in granivorous species.


L-carnitineSee Carnitine
Lactic acidAcid produced by anaerobic fermentation of undigested dietary fiber within the large
LactoseDisaccharide is the only carbohydrate of mammalian origin. It consists of a glucose and galactose molecule.
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 formula line: Emeraid.
Lamina muscularisMiddle (sometimes inner) layer of digestive epithelium
Lamina propriaOutermost layer of digestive epithelium
LecithinPhospholipids containing choline promote lipid transport in cell membranes. Used as an emulsifying
LegumesFamily of plants rich in lysine such as soybeans, beans, and peas. Legumes also contain bioflavanoids and other polyphenols that act as antioxidants.
LerpWaxy substance secreted as a protective scale by psyllids (plant lice) that is nutritionally similar to nectar
LeucineAn essential amino acid in birds. High levels (such as those found in diets high in millet) interfere with the conversion of tryptophan to niacin.
LigninInsoluble fiber found in plant stems, leaves, and skin.
LimestoneA common dietary supplement (calcium carbonate) and a form of soluble grit. Crystalline limestone is called marble.
Limiting amino
The essential amino acid that is present in the smallest proportion. In bird food, this is most commonly methionine, tryptophan, or lysine.
Linoleic acidEssential 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 acidEssential 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 oilSee Flax seed oil.
LipidInsoluble (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.
LipoproteinProtein paired with lipid that carries cholesterol through the body. Classified according to their densities as very low, low, and high-density lipoproteins.
lipoproteins (LDL)
Lipoproteins which transport cholesterol in the blood. High levels increase the risk of heart disease by promoting plaque formation and atherosclerosis.
LuteinDietary carotenoid
LycopeneDietary carotenoid
LysineAn essential amino acid in birds and most labile of the amino acids. Deficiency results in bronze pigmentation of feathers in turkey poults


MacawsSome macaws
require higher dietary fat levels. Some species may also be particularly
susceptible to the toxic effects of vitamin D.
MacrofaunivoreSpecies that eat
other vertebrates
MacromineralsMinerals required
in large quantities because they form a major part of the body’s structural
components (i.e. calcium, phosphorus, magnesium)
MacromoleculesLarge molecules
which make up the majority of the diet (i.e. lipids, fiber, proteins,
carbohydrates, and water)
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.
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.
MalnutritionSee Refeeding
ManganeseTrace 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.
MannaFluid exuded from
damaged plants which later crystallizes. Nutritionally similar to nectar.
Mazuri®A producer of a
variety of zoological products including extruded bird foods.
MESee Metabolizable
Mean retention
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 byproductsTissues such as
lung, spleen, kidney, brain, blood, bone, and intestine.
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
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.
MenadioneThe most common
form of synthetic vitamin K (vitamin K3) which has vitamin activity 2 to 3
times higher than that of natural vitamin K1.
MenoquinoneVitamin K2
synthesized by colonic bacteria.
contaminant of some types of fish such as shark, swordfish, king mackerel,
and tilefish
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)
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.
MicrofaunivoreA species which
eats invertebrates
MicromineralsA trace element
required in small amounts such as iron and iodine.
MicronutrientA substance, like
a vitamin or mineral, needed in tiny amounts.
MicrovilliSee villi
MigrationPeriod 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 thistleSee Silymarin
MilletNon-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.
MineralsThe 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 tocopherolsNaturally-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
Values assigned
for energy content of proteins and carbohydrates (3.5 kcal/g) and fats (8.5
MolluscivoreA faunivore which
primarily eats mollusks such as limpkins, snail kite, oystercatchers, and
MoltThe process of
shedding and replacing feathers associated with increased protein needs and
increased energy needs due to the loss of insulation. See Feathers.
MolybdenumTrace element
which is part of several enzymes that metabolize proteins. Dietary sources
include beans and grains. Molybdenum content in plants varies with soil
MonoglyceridesA lipid commonly
used as an emulsifying agents.
MonophagousA species which
eats only one kind of food (i.e. the Snail Kite primarily eats one species of
freshwater snail).
MonosaccharidesA group of simple
sugars (the simplest form of carbohydrate) such as glucose, fructose, or
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.
fatty acids
with one double bond such as palmitoleic acid (i.e. olive oil).
MycotoxinsToxins produced
by a fungus such as ochratoxin, oosporein, and aflatoxin.


Nasofrontal hingeMaxilla
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.
NectarDilute sugar
solution low in proteins, vitamins, and trace minerals. Predominant sugars
include sucrose, glucose, and fructose.
NectarivoreFeeding 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.
NiacinB 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.
active form of niacin.
NitrogenElement essential
for the synthesis of nonessential amino acids
metabolizable energy (MEn)
energy values corrected for the loss or retention of body protein so that
birds growing or losing weight are comparable.
Non-GMO cornAny corn hybrid
that has not been genetically modified through biotechnology procedures
Nutri-BerriesA Lafeber Company® product consisting whole grains and seeds
mixed with pellets to create a balanced product.
Nutri-MealsA Lafeber Company® product consisting of whole grains,
fruits, vegetables, and seeds mixed with pellets to create a balanced
Addition of more
nutrient improves growth, reproduction, fitness, or corrects some
pathological condition.
High levels of
one nutrient increase the requirement of another nutrient.
Nutrient toxicityNutrient levels
are high enough to induce specific pathology.
Nutrient-denseFleshy fruit with
large amounts of lipid and protein, but less water and sugar such as
avocados, palms, dates
Nutrient densityExpression of
nutrient content as grams per 100 kcal of metabolizable energy
Nutrient-diluteFleshy fruit with
a relatively indigestible skin and a large proportion of seeds.
See Dietary
NutrientsComponents 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 that
are not created by the body in quantities adequate to meet nutritional needs.
Nutrients created
by the body in quantities adequate to meet nutritional needs.
Nutritional nicheThe exact foods
consumed within a range of foods available.


Oat groatHulled oat grain
frequently added to seed mixtures for
small granivores to increase protein level (range from 15-17.5%
ObesityA common problem
in the pet bird. Species prone to obesity include galahs, budgerigars,
sulfur-crested cockatoos, Amazon parrots, and cockatiels.
Species that
consume a specific food item during their entire adult life.
OilLipids that are
liquid at room temperature.
OligivoreSpecies which
eats a limited number of foods, also known as a oligivore
OligophageSee Oligivore
OligosaccharideDifficult to
digest carbohydrates often found in plants made of 3 to 10 monosaccharide units.
Provide nutrition for intestinal flora.
Omega-3 fatty
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
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
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 eggEgg enriched with
omega-3 fatty acids. Produced by hens fed a diet which includes flaxseed.
OmnivoreA 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.
OnionFood 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
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.
OrganicFoods 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®.
OropharynxThe oral cavity
and pharynx makes up one region in the bird because there is no soft palate,
only a hard palate.
Oxalic acidCompound 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 shellSource of dietary
calcium. See Grit


Para-aminobenzoic acid
PancreasGlandular 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 acidB-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)
PapaverineAlkaloid found in
some plants.
acid (PABA)
PABA is an
essential growth factor for microbes which is needed to make folic acid.
ParasympatheticNervous system
that controls gastrointestinal motility
hormone (PTH)
Hormone which
increases bone resorption to increase calcium levels.
Intravenous or
intraosseous feeding with a modified nutritive solution directly absorbed by
cells without first passing through the gastrointestinal tract.
PasserinesSpecies 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
PeanutsOil seed highly
susceptible to mycotoxins contamination due to growth conditions in the
PectinA 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.
deficiency, See Niacin
Pellet1). 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
PentoseA monosaccharide
containing five carbon atoms which may be found in avian diets, especially
those high in fiber (i.e. arabinose, xylose)
PepsinEnzyme that
hydrolyzes protein at a variety of peptide bonds creating polypeptides.
Secreted as an inactive precursor, pepsinogen.
precursor hydrolyzed by hydrochloric acid or previously activated pepsin to
become an active enzyme.
PeptideShort molecule
created by amino acids joined together.
Persea spp.See Avocado
PhenylalanineAn essential
avian amino acid used to make melanin, epinephrine, norepinephrine, and
thyroxine. Hydroxylation of phenylalanine creates tyrosine.
Phocacholic acidSee Beta-phocacholic
PhospholipidsLipid 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
PhosphorusMacromineral found
in bone and a structural component of RNA. High dietary levels are found in
meat and eggs.
PhylloquinoneVitamin K1 found
in leafy, green plants.
Phytic acidPhosphorus
containing compound found in plants that can form indigestible complexes with
minerals such as calcium making them unavailable for absorption.
produced by plants which a variety of functions such as fibers, carotenoids, dithiolthiones,
bioflavanoids, indole carbinols, isothiocyanates, mono- and triterpenoids, and
thioallyl derivatives.
PhytophageSee Florivore
Pigeon’s milkSee Crop milk
PiscivoreType of faunivore
that eats fish
PlanktonivoreA species that
mainly eats zooplankton (also known as a planktivore)
PollenFine 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
PolypeptideA protein
containing more than three peptides bonded together
PolyphageSee Omnivore
complex compounds in plants that contain phenol groups such as
phenylpropanoids like lignins and bioflavonoids and tannins. Dietary sources
include teas, berries, and walnuts.
commonly found in plants consisting of thousands of monosaccharide units in
plants such as cellulose, starch, and glycogen. Also known as complex
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.
PolyvoreSee Omnivore
PortomicronLipoproteins used
to carry dietary triglycerides
intracellular cation
Potassium sorbatePreservative used
to prevent the formation of yeast and molds in food.
PrecocialSpecies 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.
PreservativesSubstances added
to food to protect nutrients (particularly dietary fats) from oxidative or
microbial damage under normal use and storage conditions.
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.
Examples include
butylated hydroxyanisole, butylated hydrostytoluene, tertiary
butylhydroquine, and ethoxyquin.
Pretty Bird®A producer of a
variety of bird foods included pellets.
ProbioticA preparation of
live microbes; probiotics have been recommended for prevention and treatment
of infectious diarrhea as well as prevention of antibiotic-induced diarrhea.
ProctodeumPosterior or
caudal-most region of cloaca. The bursa of Fabricious is found on the dorsal
surface of the proctodeum.
ProkinesisFlexion 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.
ProlineEssential amino
acid in growing chickens
PropionateVolatile or
short-chain fatty acid produced by bacterial fermentation of fiber. Energy
may be derived from its metabolism.
Propionic acidSee Propionate
Propylene glycolTasteless,
odorless, colorless, clear, oily liquid added to food as a humectant since it
easily absorbs moisture.
ProteinLarge complex
molecule made of hundreds to thousands of amino acids arranged as linear
polymers. Protein is the body’s primary source of nitrogen.
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.
Hydrolysis of
protein that frees amino acids
Protein reserveThe portion of
amino acids which may be mobilized from lean body tissues
Protein shiftThe increase in
protein requirements which occurs during egg production, often accompanied by
a change in food preferences
Protein turnoverThe process of
continual synthesis and degradation of protein which leads to no net change
in the amount of protein
ProventriculusGlandular portion
of the stomach that produces hydrochloric acid and pepsin to begin to break
down and emulsify foods.
analysis of foods to evaluate a limited number of parameters such as moisture
content, crude protein, crude fat, mineral content, and fiber content.
See Folic acid
Polyunsaturated fatty acids
Pyloric stomachThird,
chamber-like pyloric region below the ventriculus present in many birds that
eat fish, aquatic invertebrates, or aquatic plants.
PyridoxalOne of the three
compounds that make up vitamin B6, derived from animal tissue. See
PyridoxamineOne of the three
compounds that make up vitamin B6; derived from animal tissue. See
PyridoxineA 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


Queen of Bavaria
See Golden conure
QuinonesThe group of
compounds that make up vitamin K.


Rape seed oilSee Canola oil
RectumThe short, small
length of intestine between the ileocecal junction and cloaca. Also known as
the colon or large intestine.
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
phosphorus, magnesium, or calcium stores.
Avoid refeeding
syndrome by introducing food cautiously, monitoring clinical status and electrolytes
closely, and supplementing the diet as needed.
RefluxSee Contraction
Renal diseaseNutritional
causes of renal disease include excess dietary protein or calcium,
hypovitaminosis A, and hypervitaminosis D.
ReproductionHens laying large
clutches of eggs require large amounts of dietary protein and calcium.
Resting metabolic
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 timeSee Mean
retention time
RetinalForm 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.
RetinaldehydeRetinal pigments
formed by oxidation of vitamin A alcohols.
RetineneSee Retinaldehyde
Retinoic acidForm of vitamin A
which regulates hormonal actions
RetinoidsGroup of natural
and synthetic fat-soluble compounds collectively called vitamin A.
RetinolAn alcohol form
of vitamin A and the primary form of vitamin A transferred to the egg
Retinyl-palmitateStorage form of
retinol found in the liver.
Retrograde flowNormal reflux of
digesta in the opposite direction. See Contraction sequence
RhamphothecaThe outer horny
or keratin layer of the entire beak.
RhinothecaThe keratin layer
covering the upper beak.
RhynchokinesisBeak 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
RiboflavinVitamin 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 flourFlour relatively
high in protein and gluten-free.
RictusSoft triangle of
tissue found where the upper and lower beak meet (oral commissure).
Rosemary extractNaturally-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.


SaccharoseSee Sucrose
Safflower seedsBitter 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).
SanguinivoreSpecies that
consumes blood; this is rare among birds (i.e. Sharp-beaked Ground Finch of
the Galapagos islands)
Saturated fatty
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™.
(Short-chain fatty acids)
See Fatty acids
Second limiting
amino acid
Second most
deficient amino acid in a given food
SecretinPeptide 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.
SeedsMost 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-oilSeeds that store
most of their energy as starch and are relatively low in energy and protein
(i.e. millet, canary seed, oat groats)
Seeds, OilSeeds 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).
SeleniumTrace 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
amino acid created from dietary glycine by a reversible reaction
Short-chain fatty
See Fatty acids
SilymarinAntioxidant which
may serve to protect hepatocytes; Also known as milk thistle.
Simple sugarSee Monosaccharide
Slipped TendonSee
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 benzoatePreservative
which serves as a mold inhibitor
Sodium sorbatePreservative
which serves as a mold inhibitor
Soluble fiberFermentable fiber
sources such as pectin, gum, B-glucan, and some hemicelluloses which seem to
lower blood cholesterol levels.
Soy proteinProtein source
high in antioxidants derived from the soybean.
Soya beanSee Soybean
SoybeanLegume 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 mealCreated by
extracting most of the oil from whole soybeans. Common protein source in
modern grain-based diets fed to poultry and pet birds.
SpecialistAnimal that eats
a specific food type
Spirulina fusiformisBlue-green algae
which may be used as a source of vitamin A.
Sprouted seedsGermination of
seeds decreases phytate content (which may increase availability of calcium,
magnesium, zinc, iron, and protein), but this also increases availability of
StarchPolysaccharide of
plants used for energy storage. Cereal grains such as corn, wheat, sorghum,
barley, and rice are rich in starch.
StarvationA 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.
StenophagousBirds which
consume a narrow range of food items (ex: vulturine parrot eats fruits from one or two figs in New
Steroid alcoholSee Sterol
SterolFat and alcohol
compounds present in plant and animal tissues (i.e. ergosterol, cholesterol).
Also known as steroid alcohols.
SucroseA 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
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
Summit metabolic
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 seedOil seed that
contains niacin, unlike most seeds. Although various cultivars have different
fat levels, the darker the seed the more fat it contains.


TanninsSecondary 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.
TasteBirds 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.
TaurineA nonessential
amino-sulfonic acid in birds that may be synthesized from methionine and
butylhydroquine (TBHQ)
Highly effective
synthetic antioxidant approved for use in the United States, but not in
Canada, Japan, or the European Union.
ThiaminVitamin 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)
ThiaminaseEnzyme 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).
ThiamineSee Thiamin
ThiosulfiteToxic compound
found in onion and to a lesser extend garlic
ThreonineAn essential
amino acid in the bird
TMESee True
metabolizable energy
TocopherolsA 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
TocotrienolsA component of
vitamin E
TomiaCutting edges of
the beak
TongueMoved by hyoid
apparatus in most birds. Parrots possess intrinsic tongue muscles.
TorporTechnique 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 plus additional metabolizable energy needs for depositing tissues
associated with growth, reproduction, molt, and reserves needed for migration
or seasonal deprivation.
Total energy
A combination of
all requirements for life and its stages including growth, reproduction, and
TriglycerideA 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.
TripeptideThree peptides
bonded together
metabolizable energy (TME)
Correction of
apparent metabolizable energy for the portion of excreta that has nothing to
do with consumption of food
TryptophanAn essential
avian amino acid which is used to make serotonin and melatonin
TyrosineA nonessential
amino acid created by hydroxylation of phenylalanine


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


ValineAn essential
avian amino acid
VentThe external
opening to the cloaca; often appears as a transverse slit.
VentriculusThe 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.
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.
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.
ViscosityFiber increases
viscosity of intestinal contents. As visciosity increases, diffusion of
substrates and digestive enzymes decreases.
VitaminAn 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 AGroup 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-complexGroup 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 B1See Thiamin
Vitamin B2See Riboflavin
Vitamin B6See Pyridoxine
Vitamin B10See Folic acid
Vitamin B11See Folic acid
Vitamin B12See Cobalamin
Vitamin CL-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 DGroup 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 EFat-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 KGroup 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.
passively absorbed and transported with chylomicrons to the liver. Vitamins
A, D, E, and K
Vitamins absorbed
by active transport (vitamins C and B-complex)
See Meckel’s
synthesized by the liver of the laying hen that complexes with phospholipids
and cholesterol
Very-low-density lipoproteins
Volatile fatty
Short-chain fatty
acids: acetic, propionic, and butyric acids which provide energy when


WaterThe 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.
See Vitamins,
WeaningGradual process
of transition to a solid food diet that
occurs in response to physiologic changes of growth.
Wood sugarSee Xylose


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


YolkYellow 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).


carotenoid that gives egg yolk, <a
href=”http://en.wikipedia.org/wiki/Maize”>corn, <a
href=”http://en.wikipedia.org/wiki/Saffron”>saffron, and many other plants their
characteristic color.
ZincTrace 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
Range of
environmental temperatures at which an adult bird can maintain body
temperature without influencing maintenance energy requirements
ZoophageA 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™)