Nutritional RequirementsResearch in the area of nutritional requirements for captive-bred species is still lacking.7 Most of the nutritional studies that exist have been done on poultry. Unfortunately so many differences exist between poultry and other species of birds, that using poultry data as a basis for developing a finch diet may be dangerous,6 especially in light of the fact that poultry only consume up to 6% of their body weight daily, and finches consume up to 30%.7 For instance, research in canaries and rice finches has shown that maltase, saccharase, amylase, and lipase are all present at much higher activity levels than in poultry.7 Extrapolating a diet from the requirements for poultry to the assumed requirements for finches may therefore result in health problems.7 In addition to not having enough comprehensive species-specific information regarding diet, other complicating factors must be accounted for when designing a diet appropriate for any pet bird, including its age, reproductive status, disease conditions (if any are present), and how much exercise the bird gets.6,7 The best approach currently available for providing adequate nutrition to finches is to use a formulated diet made specifically for finches (to minimize the risk of them overdosing due to eating a diet which is too highly concentrated in certain nutrients) or to supplement a seed-based diet with food items that are considered to be successful for a particular species.7 If dietary health related problems still occur, adjustments should be made to correct them. Below is some basic information on each of the nutrients required by birds, followed by a table which details approximate "recommended nutritional allowances for granivorous (passerine) companion bird diets."
WaterFresh, uncontaminated water must be provided daily from a clean bowl, water bottle, or watering system. Water should be collected directly from a tap which has been allowed to run for at least three minutes prior to collection. This allows for the reduction of any toxic chemical buildup or bacterial presence in the drinking water.5 Vitamins should never be added to the water as they oxidize rapidly (rendering them useless), and provide a favorable environment for rapid bacterial proliferation which may be harmful to finches.2,7 Adding disinfectants and medications to the water is also discouraged.5 If watering from a watering system, flush the lines daily with water and weekly with a diluted hypochlorite (bleach) solution to keep the lines free of harmful bacteria and algae, and check that the systems are functioning daily.
CarbohydratesIn the avian body, carbohydrates serve as an energy source, and they are the only energy source that can be used by the nervous system.5,7 Therefore carbohydrate deficiencies are exhibited as neurological signs.7 If deprived of food, finches may become hypoglycemic; having a vitamin B deficiency may also worsen this problem.7
Protein and Amino AcidsAmino acids and the proteins constructed from them are needed for feather, bone, hormone, muscle, and enzyme production.7 Protein can also be used as a source of energy.6 Different species have different protein requirements; for instance, insectivorous birds generally have higher protein requirements than granivorous birds. Additionally, increased protein is required in the diets of growing and breeding birds. Regardless of the species of bird, 10 amino acids must routinely be provided to the birds, as they cannot manufacture these essential amino acids in their bodies: lysine, arginine, histidine, methionine, tryptophan, threonine, leucine, isoleucine, valine, and phenylalanine. Protein can be added to the diet through monkey biscuit, boiled egg, and/or live food. Egg is one of the few protein sources available that can be optimally utilized because its amino acid profile is similar to that of the bird's body.5
Fats and Essential Fatty AcidsEssential fatty acids are required by the avian body in the production of membranes and cell organelles and as precursors for prostaglandins; other fats are used as an energy source.5,7 Linoleic acid is the primary essential fatty acid for birds.5 Although many birds seem to tolerate a wide range of fats in their diet, diets which are too high in fat may lead to obesity and other complications including interfering with the absorption of other nutrients such as calcium, and diets which are too low in fat may lead to decreased weight and disease resistance among other problems.7 Rancid fats reduce amino acid availability and may contain only destroyed essential fatty acids;7 never feed your birds any fat source which has a fetid odor.
VitaminsVitamins are organic trace nutrients that usually have either hormone or cofactor functions in the body;6 they are divided into two categories: fat-soluble vitamins and water-soluble vitamins. The fat-soluble vitamins, which are stored in the body longer than the water soluble vitamins,6 are vitamin A, vitamin D3, vitamin E, and vitamin K. Fat soluble vitamins are particularly tricky to supplement because overdosing a bird is relatively easy to do and can result in toxicity. Vitamin A is responsible for mucopolysaccharide biosynthesis, aiding in the formation of normal mucous membranes and epithelial surfaces, as well as for growth, vascular development, adrenal hormone production, vision, immune response, and the formation of the red and yellow pigments in feathers.5,7 Plants contain precursors to vitamin A in the form of carotenoid pigments (such as beta carotene); because the avian body will not convert these precursors to active vitamin A unless there is a need for it, carotenoids in the diet do not contribute to potential vitamin A overdose.5 Vitamin D3 (cholecalciferol) is the active form of vitamin D in birds; it is formed through the action of sunlight on non-feathered parts of the bird's skin or in oil from the preen gland.6,7 This action converts ingested vitamin D precursors to the active form of vitamin D, which is then absorbed through the skin or consumed during preening.6,7 This means that if adequate lighting is provided to birds, dietary supplementation of vitamin D3 is unnecessary except in growing and egg-laying birds.6 Vitamin D3 is responsible for calcium absorption, mobilization, and reabsorption.7 Vitamin E (principally in the form alpha-tocopherol in birds)5 acts mainly as an antioxidant and helps protect cell membranes. It interacts with selenium, and the two nutrients spare each other in the diet, although neither can be completely eliminated and replaced with the other.6 The need for vitamin E may increase with malabsorption syndromes (such as protozoan infections in the intestines), with consumption of large amounts of polyunsaturated fat, and with consumption of rancid fats.6,7 Vitamin K is normally produced by the intestinal bacterial microflora, and is needed in part for the synthesis of clotting factors.7 Contrary to popular belief, passerine species do not have an obvious, permanent bacterial intestinal flora,7 and may therefore need this vitamin to be provided in the diet.
Water-soluble vitamins include thiamin (B1), riboflavin (B2), niacin, pyridoxine (B6), pantothenic acid, biotin, folic acid, vitamin B12, choline, and vitamin C (ascorbic acid). Because water-soluble vitamins can be excreted in the urine, toxicity is less likely to occur and reasonable supplementation poses little risk (over-supplementation of choline has been associated with mortalities, however).7 Thiamin, used for nerve transmission, occurs in low concentrations in many plant food sources.7,5 Some food preservatives and tannic acid have anti-thiamin activity and may lead to deficiency if present in the diet.7 Riboflavin is part of coenzymes that act in a large number of essential reactions in the utilization of carbohydrates, fats, and proteins.5 Inadequate amounts of riboflavin in the diet may lead to poor growth, rough, dry skin, and curled toe paralysis (in poultry) among other problems.6,7 Riboflavin is likely to be limiting in seed diets fed to laying hens,6 and riboflavin toxicity is highly unlikely.5 Niacin is part of coenzymes involved in reactions which are critical for energy generation and normal tissue integrity.5 Animal sources of niacin are preferable to plant sources because the niacin present in plants has low bioavailability.5 Additionally, diets high in millet, which contains high amounts of leucine, may lead to pellagra as high levels of leucine interfere with the conversion of tryptophan to niacin.6 Inadequate amounts of niacin and pyridoxine in the diet may lead to poor growth as well as neurological symptoms.7 Pyridoxine is required in nearly all areas of amino acid utilization as well as the formation of antibodies.5 Pantothenic acid is used to form Acetyl CoA which is used in many metabolic reactions.5 Biotin is used in the formation of critical enzymes in CO2 metabolism.7 Raw egg white contains avidin which inhibits biotin; egg whites should always be cooked, therefore, before being fed to birds.7 Biotin deficiency may also be associated with wheat and barley, and has been implicated in fatty liver and kidney syndrome.6 Mold in the diet and rancid fat may increase the need for biotin in the avian body.6 Folic acid is used in the biosynthesis of amino acids and nucleotides as well as in the production of white blood cells; folates are widely available in many grains.5,7 Vitamin B12 (cyanocobalamin) is critical in many metabolic pathways including the synthesis of protein, nucleic acid, fat, and carbohydrate.7 Produced by bacterial biosynthesis, vitamin B12 may be found in muscle, peas, beans, and spirulina.7 Choline is essential, but deficiencies are unlikely to be encountered because it is widely available. Additionally, over-supplementation may lead to mortality. It is used in production of phospholipids and cartilage, and is required for acetylcholine.5,7 Although most birds are capable of synthesizing vitamin C, some species cannot. Passerines are thought to be some of those birds that require ascorbic acid in the diet.6 Because ascorbic acid is safe to use, it should be administered regardless of dietary requirement to be on the safe side.6 Ascorbic acid is essential for a large number of enzymatic reactions, such as those involved in maintaining collagen and elastin in blood vessel walls.6
MineralsMinerals used by the avian body include: calcium, phosphorus, magnesium, iron, copper, zinc, selenium, manganese, iodine and sodium and chlorine. Because they are toxic at levels slightly above their requirement, great care must be taken when supplementing minerals.6 Calcium is essential for muscle function, blood coagulation, eggshell and bone formation.7 Parathyroid hormone and vitamin D3 regulate calcium's absorption from the intestinal tract.7 High-fat diets, phytate (present in grain), phosphates, and oxalates (present in spinach and some other leafy green vegetables) all decrease the avian body's ability to absorb calcium.7 Phosphorus and calcium need to occur in a specific ratio range in the avian body in order to work together correctly. Too much phosphorus in the diet will interfere with calcium absorption from the intestinal tract.7 The calcium to phosphorus ratio should be around 2:1 in adult, non-breeding birds.6,7 Growing and egg-laying birds may need a slightly higher calcium to phosphorus ratio.2 Phosphorus deficiency is not likely to occur because phosphorus is present in many plant foods, although most of it may not be utilizable by the avian body because it is often bound as phytate (generally, phosphorus from plant sources is 30-40% available).7,6 The demand for magnesium in the body increases with increased levels of calcium or phosphorus;6 magnesium is needed in the body to aid phosphate transfer.7 Cellular respiration is partially dependant on hemoglobin, for which iron is needed.7 Copper is also needed for hemoglobin synthesis, as well as in the formation of enzymes such as those which synthesize melanin.7 Insulin and many enzymes in the body require zinc to be present.7 In addition to being linked to the production of thyroid hormones, selenium is part of an enzyme which acts as an antioxidant.7 Manganese is necessary for normal bone and eggshell formation, as well as normal growth and reproduction; excess dietary calcium and phosphorus may interfere with its uptake.7,6 Iodine is required for the formation of compounds in the thyroid gland that are related to thyroxine.7 Lastly, sodium and chlorine function to maintain homeostasis in the body (proper osmotic pressures and acid/base balance).5