The nutrients that comprise a quail diet are water, protein, carbohydrate, fat, minerals, and vitamins. Although all are essential, adequate water may be considered the single most important nutrient. Fresh clean water should be provided continuously to all birds, especially under the tropical environment. Quails require at least twice, as much in weight of water as they require in weight of dry feed (Farrell et al., 1982). They may require more water if there are excess salts in the feed or during ho t dry season.

Protein.
Protein provides the amino acids for tissue growth and egg production. The dietary protein requirement of quail is influenced by metabolizable energy content and the ingredients used to formulate the diets. The earlier investigators raised their quail f locks successfully on turkey starter diets containing about 25-28% crude protein (Wilson et al., 1959; Woodard et al., 1973; NAS, 1969). Lee et al. (1977a & b) have shown that a dietary crude protein level of 24% is needed in starter diet for quail and t he protein content may be reduced to 20% by 3rd week of age.

Protein is the most expensive nutrient and must be provided from a high quality source. Protein quality is generally based on the amino acid composition of the feedstuff and the availability of these amino acids from the feedstuff through digestion in the gut of the quail. Amino acids are considered as the building blocks of proteins. Out of 19 total amino acids required by quail, 13 are considered as essential amino acids, because they cannot be produced in the quail's body and must be supplied in the diet, and 6 are considered as nonessential, because they are synthesized by the body and need not be supplied in the diet. The 13 essential amino acids are: arginine, cystine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, th reonine, tryptophan, tyrosine and valine. Feedstuffs differ qualitatively and quantitatively in their amino acid composition. Quail diets consist mainly of plant materials. The most commonly used plant products are maize, soyabean meal, sorghum and rice or wheat bran. Methionine and lysine are generally low in plant products. Animal protein products such as fish meal, meat and bone meal etc., are good sources of most of the essential amino acids, but they are usually more expensive than plant protein ingredients. Synthetic methionine and lysine are usually added to the diets to balance the amino acid composition (Shim and Lee, 1984a & b; 1988a & b).

Energy.
The amount of food intake depends upon the metabolizable energy (ME) content of the diet, age of the birds, their reproductive status and the ambient temperatures. An energy requirement of 2,600 to 3,000 kcal ME/kg diet for growing quail has been reported from temperate regions (Farrell et al., 1982; Young et al., 1978), whereas, findings under our tropic condition indicated an energy requirement of about 2,800 kcal ME/kg for growing quails (Shim and Lee, 1982a) and 2,550 kcal ME/kg for laying quails (Shim and Lee, 1982b). Though raising the dietary energy levels from 2,600 to 2,800 kcal ME/kg did not influence the gain in weight, it affected significantly the efficiency of feed utilization as the feed consumption was reduced significantly (Shrivastavand Panda, 1982).

The main energy source is provided by the grains and cereals which are the main ingredients in most feed. Fat such as animal tallow, lard or other vegetable oils are added to the diet if high energy is required by the quail.

Vitamins.
Vitamins may be categorized as fat soluble, (A, D, E, and K) and water soluble (the B-complex vitamins). Many vitamins are quite stable, but some deteriorate rapidly on exposure to heat, sunlight, or air. Housed quails are entirely dependent on the vitamins that are present in their compounded feed in the correct amount and proportions, for they have no access to the natural supply of these nutrients. The principal vitamin functions and requirements are as follows:

Vitamin A.
The principal feature of vitamin A is its function in ensuring adequate growth and as a means of assisting in the birds' resistance to disease. Vitamin A is essential for normal vision, egg production, and reproduction. Laying quails receiving insufficient vitamin A produce fewer eggs and eggs produced frequently do not hatch. For egg production and fertility of females, a level of 2,500 I.U. vitamin A/kg diet was required (Parrish and Al-Hasani, 1983). The hatchability and survival of newly-hatched c hicks were better with 3,200 I.U. vitamin A/kg diet.

True vitamin A exists only in animal kingdom. It may be formed by synthesis in the body of the bird from the precursor, carotene, which present in green vegetable matter or yellow corn. Because it increases exposure to air, grinding of feed materials will hasten the deterioration of this vitamin during storage, particularly if storage areas are warm or hot. As a result, the feed industry does not depend upon the bird's receiving their vitamin A from ingredients in the diet. Dry or stabilized vitamin A is added to diet to meet the requirements of the bird. The supplementation of 4,000 I.U. vitamin A per kilo of diet for quails may be adequate for their optimum growth, production and reproductive traits.

Vitamin D.
This vitamin has several forms, but D₂ and D₃ are the most important. Vitamin D₃ is utilized by birds, man, and four-footed animals, while vitamin D₂ is of value to man and four-footed animals. Thus D₃ becomes essential for quail. Vitamin D aids the absorption of calcium and phosphorus form the intestinal tract and the deposition of calcium on eggshell.

Vohraetal. (1979) observed that dietary deprivation of supplementary vitamin D₃ did not affect body weight of male and female Japanese quail despite a reduction in feed intake. However, the production of eggs was reduced from 74% to 20%. In another experiment, the mature male quail remained in good physical condition on practical diets devoid of vitamin D3 for 1 year. But a mortality of about 90% was observed in females and 16% in males even when both were in negative calcium balance of about the same order (Chang and McGinnis, 1967).

Vitamin D is associated with sunlight, for sunlight provides irradiation that stimulates the manufacture of vitamin D in the skin of the bird. Unfortunately, laying quails are seldom exposed to direct sunlight, so the body synthesis of vitamin D is limit ed. The quail producer normally adds vitamin D to the quail diet in required amount to meet productive objectives rather than relying on synthesis or feed ingredients.

Vitamin E.
A deficiency of vitamin E causes a disease of the nervous system in chicks known as 'crazy chick disease' (encephalomalacia). It is also essential to breeding stock for the good hatchability of their eggs. Encephalomalacia occurs when the diet contains unsaturated fats that are susceptible to rancidity. Several antioxidant compounds, in addition to vitamin E, are usually added to prevent the fat from going bad.

The essentiality of vitamin E for quail was demonstrated by Price (1968), Cunningham and Soares (1976), Kling and Soares (1980) and Shim et al. (1983). A deficiency of vitamin E in semi-purified diets containing isolated soybean protein and starch did no t affect the body weight, feed consumption, or egg production of Japanese quail. However, it caused sterility in males, which was overcome by restoring 40 I.U. vitamin E/kg to the diet for about 2 weeks. The fertility and hatchability of quail eggs were severely depressed after the birds were fed a conventional diet containing glucose and soybean meal, but deficient in vitamin E for 20 weeks. No encephalomalacia or muscular dystrophy were observed in quail fed vitamin E deficient diets for 35 weeks.

Whole grains and alfalfa meal are the best natural sources of vitamin E. Synthetic tocopherols (vitamin E) are available, and these are usually added to quail starter and breeder rations.

Vitamin K.
Vitamin K is an essential element in the synthesis of prothrombin, a chemical necessary for blood clotting. A deficiency can lead to the rupture of blood vessels and causing excessive bleeding. It is present naturally in all green foods, especially rich in lucerne meal. The needs are small, and 2 i.u./kg will suffice under normal conditions. A synthetic, water-soluble form of vitamin K3 is generally added in the diet.

Vitamin B complex.
The B vitamins are well distributed in cereals and grains, and deficiencies are normally unlikely to occur. The main functions of the B vitamins are to assist the quail in achieving its optimum growth.

Thiamin (vitamin B₁) is needed for the metabolism of carbohydrates. Charles (1972) reported classical symptoms of polyneuritis in newly hatched quail chicks from a flock fed turkey breeder diet calculated to contain 3.2 mg thiamin/kg. These quail responded positively to thiamin injection. Breeding Japanese quail may have a higher requirement for thiamin (Shim and Boey, 1988) than breeding fowls which is reported to be 0.8 mg thiamin/kg diet (NRC, 1977).

Riboflavin (vitamin B₂). Ramchandran and Arscott (1974) suggested a minimum requirement of 8 mg riboflavin/kg diet in absence of vitamin B12 and vitamin C, but it decreased to 4 mg per kg in presence of these vitamins. The characteristic symptoms of riboflavin deficiency were slow growth, high mortality, impaired gait and posture which is known as 'curled toe paralysis' in quails. Feathering was absent other than down at the end of two weeks of riboflavin deficiency.

Shim (1985) studied the maternal riboflavin deficiency on reproductive and embryonic development in Japanese quail and found high mortality in the riboflavin deficiency group. The 4 and 8 mg/kg of riboflavin were sufficient to maintain normal egg product ion. Data obtained in weekly hatches showed that the addition of small quantities of riboflavin supplement to the basal ration increased the incidence of curled-toe paralysis whereas larger amounts decreased it.

Nicotinic acid. Park and Marquardt (1982) fed a nicotinic acid-free diet to 4 week old quail and found a subsequent depression in growth, but no other classical deficiency symptoms. However, newly-hatched quail chicks diet within 9 days of this deficient diet. The age of the birds determines the severity of symptoms of nicotinic acid deficiency. A marked depression in growth, closure of eyes, reduced activity and a marked atrophy of the pectoral muscle were observed in quail on nicotinic acid deficient diets. Ramchandran and Arscott (1974) suggested a level of 40 mg per kg diets for normal growing quails.

Pantothenic acid. A supplementary level of 7.5 mg calcium pantothenate/kg diet was needed in purified diets for prevention of mortality and for normal growth of quail chicks, but 10-30 mg was needed for normal feathering (Curler and Vohra , 1977). On the other hand, Spivey-Fox et al. (1966) found the requirement to be 40 mg/kg diet for quail up to 5 weeks of age.

Breeding quail needed 15 mg supplementary calcium pantothenate per kg diet for optimal fertility and hatchability. Eggs from pantothenic acid deficient hens were characterized by embryonic mortality late in incubation period, haemmorhagic embryos, oedema and embryos with crooked legs (Cutler and Vohra, 1977).

Choline. Growing Japanese quail required higher levels of dietary choline to support maximum growth, prevent perosis (Ketola and Young, 1973), maintain maximum egg weight (Latshaw and Jensen, 1971), egg production and hatchability (Latshaw and Jensen, 1972) than chickens. Mature quail differ from laying fowls as they require performed choline. The suggested requirement of quail for egg laying is about 3,100 mg/kg diet.

Folic acid. Folic acid deficiency in growing quail caused poor feathering, high mortality, leg weakness and cervical paralysis. These symptoms were similar to those observed in turkey poults. Quail chicks also suffered from a mild anaemia , and a curled toe syndrome. The folic acid requirement of growing quail was between 0.3 to 0.36 mg/kg casein-gelatin based diet (Wong et al., 1977).

Biotin. Dobalova et al. (1983) reported the need of supplementary biotin for gain in body weight of quail and for increase in egg production.

Vitamin B₁₂ (Cobalamin). vitamin B₁₂ is required for the development of normal red blood cells. For better hatchability, sufficient pantothenic acid and vitamin B₁₂ are also essential.

Substantial quantities of vitamin B complex are found in all the ingredients in feed. It should be stressed that vitamin B₁₂ is found only in foods of animal origin. The levels required by quails for the major B vitamins are shown in Table 1.

Minerals:

Besides protein, carbohydrates, fats, and vitamins, many other elements form a part of the quail's nutritional requirements. Minerals can be divided into macrominerals and microminerals. Macrominerals are required in large amounts, and are often struct ured parts or acid-base elements. These are: calcium, phosphorus, potassium, magnesium, sulfur and salt (NaCl). The microminerals are associated in activation or integrated parts of enzymes. These include: cobalt, copper, iodine, iron, manganese, selenium and zinc. Minerals make up 3 to 5% of the quail's body. Since minerals cannot be synthesized, they must be provided by the diet.

Calcium and phosphorus. The main function of these two minerals is in the make-up of the bones of the body. Calcium is also essential for the deposition of egg shell. It is not only that calcium and phosphorus are required in sufficient quantity but also in the correct proportions. For the young growing quail the ratio should be 1:1 to 2:1. The young quail needs a minimum of 0.8 per cent of the diet as calcium and 0.45 per cent as available phosphorus, whilst the laying quail needs about 2.5% to 3% of calcium since this is the main constituent of the egg shell (Nelson et al., 1964).

Miller (1967) observed no difference in body weight or bone ash of quail up to 6 weeks of age as long as the diets contained 0.58% to 1.18% total phosphorus and 0.44% to 2.3% calcium. Lee and Shim (1971) found that 0.5% calcium was adequate for the growing quail and a level of 4.9% calcium retarded growth. Ong and Shim (1972) observed that growing as well as laying quail were in positive calcium balance as long as the diets contained 0.8%, 1.5%, 2.6% or 3.5% calcium. A level of 3.5% dietary calcium reduced hatchability.

Minerals are present in many of the ingredients in the diet. Fish meal, meat and bone meal, milk products are good supplemental sources of calcium and phosphorus. Oystershell, limestone, tricalcium phosphate or calcium carbonate are usually added to the feed to supplement these elements.

Magnesium. Magnesium is an essential constituent of tissues and body fluids. Its ions serve as activators of important enzymes involved in intermediary metabolism. When it is absent from the diets, quails grow slowly, exhibit convulsions and may eventually die (Harkabd et al., 1976). Deficiencies in laying rations produce a rapid drop in egg production. The magnesium requirement was recommended to be 300 mg/kg diet. In the studies of Vohra (1972), magnesium requirement for survival and growth was met by supple menting 150 mg magnesium per kg diet, or 50 mg magnesium per liter drinking water. Sughara et al. (1982) found no detrimental effects from feeding 1,000 mg magnesium per kg purified diet.

Natural feedstuffs contain adequate amount of magnesium. Some limestone (the dolomites) contain a high percentage of magnesium and are to be avoided because excess magnesium is laxative and interferes with calcium usage.

Manganese. The main function of manganese is to prevent perosis, a condition where the Achilles's tendon slips off its groove behind the hock joint, pulling sideways and backwards. It is also required for normal growth, egg shell deposition, egg production and good hatchability. It is supplemented in the diet in the form of manganese sulphate.

Iron, Copper and Cobalt. These trace elements are essential for the formation of haemoglobin. Nutritional anemia occurs when there are deficiencies of these minerals. The red blood cells contain iron. Copper is necessary for iron utilization when haemoglobin is formed. Harl and et al. (1973) reported the iron requirement of growing Japanese quail as 90-120 mg/kg, and of copper as 5 mg/kg diet based on EDTA extracted isolated soybean protein.

Cobalt is the integrated part of vitamin B12 which involves in haemoglobin formation. The amount of these elements in the diet is quite specific; excesses may be toxic. Usually, only small amounts are added in the feed. Mackova et al. (1981) studied the effect of supplementary 50, 100, 250 and 500 mg cobalt sulphate per kg diet on vitamin B12 concentration in liver and caeca. The concentration was highest with 1200 mg cobalt sulphate/kg diet.

Selenium. Selenium is an essential element for growing quail even in presence of vitamin E. Diets consisting of amino acids and 100 mg d-alpha-tocopheryl acetate/kg needed to be supplemented with 0.1 mg selenium as selenite for proper survival of quail (Thompson and Scott, 1967).

Impaired reproduction was observed in Japanese quail fed a diet low in selenium and vitamin E from hatching to maturity. Oviposition rate and fertility were not affected, but the hatchability of fertile eggs, viability of male and female adults and newly hatched chicks were reduced. Dietary supplementation with either 1 mg selenium or 30 I.U. vitamin E/kg diet prevented the impaired reproduction (Jensen, 1968). Selenium supplementation of the diet at 0.2 mg/kg diet prevented nutritional pancreatic atrophy and resulted in significant elevation in SeGSHpx activity (Shim, 1985).

Zinc. Japanese quail are quite sensitive to a dietary deficiency of zinc. Zinc deficiency in quail chicks was characterized by slow growth, abnormal feathering, labored respiration and an in coordinated gait, low tibia ash, and a low concentration of zinc in liver and tibias. The zinc requirement for normal growth, feathering, tibia length and conformation was 25 mg/kg diet (Spivey-Fox and Jacobs, 1967). Harland et al. (1975) studied the protective effect of a high prior zinc intake for rapidly growing quail to a subsequently fed low zinc diet. The birds fed an initial level of 75 mg zinc/kg grew significantly better than those fed initially 25 mg zinc/kg. Bone might store zinc and it might be mobilized during zinc deprivation. A reduction in zinc absorption in adult quail by high levels of calcium was reported by Kienholz et al. (1965).

Salt (Sodium chloride). This is needed for protein digestion and these elements are also involved with acid-base equilibrium in the body. The growing Japanese quail fed a purified type of diet containing 0.042-0.051% sodium had poor growth , high mortality, adrenal enlargement, elevated haematocrit, and depressed plasma sodium suggestive of an aberration in fluid and electrolyte haemostasis. A dietary sodium level of 0.1% overcame these difficulties (Lumijarvi and Vohra, 1976).

Natural feedstuffs usually require supplemental feeding of salt (NaCl) to satisfy the quail's requirement for sodium and chloride and this is normally added to the feed at amounts of 0.25 to 0.35 per cent. Too much salt produces a laxative effect and results in wet droppings and also wet litter.