Nutritional Deficiencies and Diseases of Poultry

New Zealand Journal of Agriculture, Volume 82, Issue 2, 15 February 1951, Page 181

Nutritional Deficiencies and Diseases of Poultry

THE artificial conditions under which poultry flocks are reared and kept necessitates careful attention to the composition of a diet not only complete in proteins, carbohydrates, and fats, but also containing certain essential accessory food substances (vitamins and minerals). Extremely small amounts of these substances are required, but their absence or deficiency in the ration gives rise to fairly definite disease symptoms. In this article by J. J. Thompson, Veterinarian (Poultry), Department of Agriculture, Wellington, only the deficiencies likely to occur under ordinary New Zealand feeding conditions are discussed.

MODERN commercial poultry keepers in many cases favour the housing of poultry under intensive conditions which prevent the birds from correcting the lack of essential elements in the diet by grazing on pasture. This has led to considerable research into poultry nutrition to establish the complete requirements of chicks,- growing stock, and laying and breeding birds. From this study has emerged a mass o'f scientific information which makes the subject of poultry nutrition and its effect on the health and productivity of the fowls very complex. Fortunately, relatively little of this information need concern the poultry keeper. By emphasising the practical essentials to the exclusion of the remainder and reducing the scientific technicalities to simpler terms, stress is placed on the elements necessary in the normal diet. All the minerals and vitamins required for feeding poultry are contained in the foodstuffs in common use. Preparation of a balanced ration which will supply the necessary nutrients consists largely of making intelligent use of these foods in the proper proportions. ■ A good diet is one which keeps the bird healthy and sustains its natural resistance to disease if management is good. The unbalanced diet makes the flock more susceptible to diseases of bacterial origin, coccidiosis, worm parasites, and colds. MINERALS Numerous mineral elements are required by poultry. They enter into

the composition of bone, the functions of the organs, and clotting of the blood, and are necessary for the maintenance of life and reproduction. The essential minerals are calcium, potassium, magnesium, phosphorus, zinc, chlorine, sodium, manganese, iodine, iron, copper, sulphur, and cobalt. The ordinary constituents of rations contain most of these elements in sufficient quantity. Calcium, phosphorus, sodium, chlorine, and manganese are the only minerals which require practical consideration. The feeding of minerals in excess may have harmful effects. Calcium (Lime) The important part played by calcium in the composition of bone and egg shell underlines the necessity for the inclusion of this mineral in the rations of both growing and laying stock. Deficiency of calcium in the diet of young stock leads to poor growth and rickets. In laying stock it causes poor egg-shell quality, lowered production, and poor hatchability. Growing stock require 1 per cent, of calcium in the ration. To meet the needs of egg-shell production laying stock require a higher percentage, and the recommended amount is 21 per cent, of the ration. This is usually supplied by adding up to 1 per cent, of ground limestone, shell grit, or oyster shell to the mash and supplying the remainder in troughs. Confusion is sometimes encountered through the use of the term grit to cover two different substances. Soluble or shell grit such as oyster shell or limestone grit is used to supply the

calcium requirement. Insoluble or hard grit is necessary if whole grain or coarse feed is supplied; it is stored in the gizzard and assists the grinding action of that organ in breaking down large food particles such as grain, leading to more efficient digestion of the food material. Granite chips or gravel are good types of hard grit and should be made available for laying birds to eat at will. For chicks coarse sand is useful.

Grains and their by-productsbran and pollardhave a poor calcium content; meat meal and fish meal contain a relatively high percentage. A large excess of lime in the diet affects hatchability adversely and may also cause digestive upsets. Phosphorus Phosphorus is also necessary for bone formation, and occasional cases of rickets are caused by deficiency. The close association of calcium and phosphorus in the formation of bone and in the body metabolism is well established and they are usually considered together. The utilisation of both minerals depends on the presence of adequate vitamin Din the ration. If sufficient vitamin D is not present, calcium and phosphorus are not deposited normally in the bones of the chicks, leading to rickets. Because of their close relationship a ratio between the two minerals has been laid down. This ratio is generally accepted at 14 to 2 of calcium to 1 of phosphorus for growing birds. The higher requirement of calcium by laying birds because of shell production necessitates a higher ratio. i If a vegetable protein concentrate such as ground nut meal is fed, the inclusion of bone meal in the ration may be necessary. Meat meal, fish meal, bran, and pollard are good sources of phosphorus and rations in which these form a considerable part do not require any phosphorus supplement. .

MINERAL AND VITAMIN DEFICIENCIES IN POULTRY

Excess phosphorus feeding affects chick growth adversely because of cal-cium-phosphorus unbalance. The feeding of excess bone meal with its high phosphorus content, which “fixes” the manganese in the diet so that it is not available to the birds, may give rise to perosis (slipped tendon). Salt (Sodium Chloride) The addition of salt to the diet meets the requirements of poultry for both sodium and chlorine. Salt should be added to the mash at the rate of J per cent, for an all-mash ration or 1 per cent, for a mash-grain ration.' If fish meal forms a high proportion of the protein supplement, the addition of salt to the mash is unnecessary. Contrary to popular belief, poultry tolerate salt in the feed reasonably well and up to 8 per cent, has been fed to growing chickens without harmful effects. Nevertheless, care must be taken that the salt is well distributed in the mash. Deficiency of salt causes slow growth and lowered egg yield and may initiate an outbreak of feather picking and cannibalism. Increasing the salt content to 3 to 4 per cent, of the mash for 4 days is effective in controlling some outbreaks of cannibalism.' Manganese One of the trace elements, manganese is present in only minute amounts in foodstuffs. The manganese required in the diet is amply supplied by a content of 50 parts per million (.0005 per cent.) The essential nature of manganese in the diet is evident from the effects of deficiency. Manganese is necessary in the ration to prevent perosis in young stock and is essential to ensure high hatchability. It also affects the building up of the other essential minerals of the body, egg production, and egg-shell quality. If bran and pollard form a considerable part of the ration, supplement-

ing the diet is unnecessary, as mill offals are good sources of manganese. If a manganese supplement is required, it should be supplied at the rate of 4oz. of powdered manganese sulphate to 1 ton of mash. A convenient method of mixing it in the mash is to add 4oz. of manganese sulphate to 101 b. of salt and use the mixture in place of salt alone in the diet. Effects of Manganese Deficiency The obvious symptoms of perosis (slipped tendon or hock disease) are swelling of the hock joints and twisting of the leg bones; in an advanced case the tendons slip off the angle of the hock joint. In general the symptoms do not develop until the age of 4 or 5 weeks, and a tendency to squat on the hocks for prolonged periods may be the first apparent sign of trouble. Perosis is common in turkeys and may affect ducklings as well as chicks. It has been found that, though manganese is the principal agent in preventing perosis, several other organic factors such as biotin, folic acid, and choline are also necessary. However, these are seldom deficient in ordinary rations and perosis is unlikely to occur if the manganese content of the diet is sufficient. Egg production falls in adult birds on a diet deficient in manganese, and they produce eggs that have thin, fragile shells and show poor hatchability. Embryonic mortality occurs from 10 days onward and frequently chicks which do hatch are deformed. VITAMINS Though most of the work on vitamins has been carried out within the past 40 years, disease symptoms caused by food deficiencies are said to have been recognised by the Chinese as early as 2600 B.C. Much of the research work on vitamins has been biological, and the suitability of chicks as experimental subjects has led to

the building up of an extensive knowledge of their requirement. Most of these —thiamine, pyridoxine, nicotinic acid,, pantothenic acid, vitamin K, biotin, folic acid, and choline —are present in sufficient amounts in normal rations to warrant dismissing them in favour of emphasising the three vitamins most frequently deficient; these are vitamins A and D and riboflavin (also known as vitamin Bo and vitamin G). Vitamin A Field and laboratory findings indicate that vitamin A is the most important vitamin and the one most often deficient in poultry diets in New Zealand. The necessity for a constant and adequate supply of vitamin A in poultry rations is based on a number of factors: — Vitamin A is needed to maintain the normal lining of the eyes, respiratory tract, and upper part of the digestive tract in a healthy condition. As these covering membranes have a protective function and constitute the “first line of defence” against infection, vitamin A is frequently called the antiinfective or protective vitamin. Dietary sufficiency of vitamin' A has been shown to increase the fowl’s resistance to the large roundworm and intestinal coccidiosis. Lack of vitamin A causes “nutritional roup” and is frequently a predisposing factor in outbreaks of colds and contagious catarrh or coryza. Vitamin A affects egg production and possibly hatchability. When supplied in sufficient amounts to , breeding stock it is passed on through the egg to the chicks. The principal sources of vitamin A available to the poultry keeper are fortified fish oils and suitable greenfeed.

A pound of oil is about a pint and loz. about 2 tablespoonfuls.

VITAMIN A DEFICIENCY IN POULTRY

Greenfeed

Vitamin A does not occur as such in greenfeed, but is present in the form of carotene, a pigment which occurs also in carrots, yellow maize, and pumpkins. Carotene is converted in the body to vitamin A. Sufficient carotene is contained in about 2oz. of good, fresh, young greenfeed to supply the daily vitamin A requirement of a bird. Old. fibrous greenfeed is of no value and may give rise to digestive upsets,

including impaction of the crop and gizzard. Fairly rapid loss of carotene occurs if the material is cut and stored before being fed, especially in warm weather.

Though the main value of greenfeed lies in its carotene content, it is also a useful source of riboflavin and a number of other vitamins, including pyrodoxine, vitamin E, vitamin K, pantothenic acid, and folic acid. The pigment xanthophyll, which is responsible for egg-yolk colour, is also contained in greenfeed. Vitamin A Concentrate Oils and Emulsions During certain seasons of the year, and particularly after a spell of hot, dry weather, the greenfeed supply may be inadequate as a source of vitamin A, and the use of a fortified or concentrate fish oil is then advisable. These oils, because of their concentration, are also of special value in supplying the vitamin A requirements of young chicks. The value of a fish oil depends on its potency; that is, the declared vitamin A content. The potency should be found clearly stated on the label of the container, and an oil may contain from 1000 to 5000 international units of vitamin A per gramme. Occasionally the amount of vitamin A is stated in units per pound of oil, in which case the number of units should be divided by 450 (lib. is approximately equal to 450 grammes) to ascertain the number of units per gramme. Obviously, if a 5000-unit oil is used, the quantity required to supply the dietary needs for vitamin A is less than that of a 1000-unit oil.

The quantity of vitamin A-rich oil fed in the mash depends on the potency of the oil, whether an allmash ration or a mash-grain ration is used, and the age of the stock. The table of dosages on this page, compiled by McClymont, of the New South Wales Department of Agriculture, in “Scientific Feeding of Poultry”, has been modified in accordance with the recommendations of the National Research Council and is based on the optimum requirements of different classes of stock. Growing stock require 2000 international units per pound of food, laying stock 3000, and breeding stock 4500.

Some poultry keepers calculate the quantity of oil required per 100 birds instead of per 1001 b. mash. It is then necessary only to estimate the amount of food consumed by 100 birds, which at the normal rate of . 4oz. per bird would be 251 b. and calculate the dosage required accordingly. Proper storage of vitamin A-rich oils is very

important. Oxidation by exposure to air may cause a reduction in the vitamin A content of up to 0.70 per cent, in 10 days and should be prevented as far as possible by efficient stoppering and storing in a cool place. Buying oils in large quantities is inadvisable if it means long storage. The oil should be mixed with the feed twice a week, as the vitamin A is destroyed fairly quickly after being mixed with the ration.

Emulsions of vitamin A oils have now become available in New Zealand. Such emulsions have the advantage of being miscible with water and may be added to the water used to prepare a wet mash.

Vitamin A oils or emulsions are of special value during periods of greenfeed shortage or where the greenfeed is of doubtful quality. The added vitamin D makes it invaluable as a certain source of both vitamins in the concentrated rations of young chicks.

Greenfeed, however, is not completely replaced by vitamin-rich oils, and where it is available and of good quality it should be used in the ration. As a source of riboflavin and xanthophyll, which gives colour to the egg yolk, it is a valuable addition to the feed.

Effects of Vitamin A Deficiency

Complete deficiency of vitamin. A or any of the other necessary vitamins leads to a train of fairly distinct symptoms, but where the deficiency is less severe diagnosis may be difficult. The only evidence of lack of essential vitamins in the diet may be unthriftiness, lack of growth, and failure to thrive, possibly associated with unusually high mortality in chicks. In laying stock border-line deficiency results in lowered egg production.

Evidence of severe deficiency of vitamin A is not usually observed until chicks are about 3 weeks old. However, if the diet of the parent stock has been deficient in vitamin A, with resultant poor storage in the egg, the effects may show at an earlier stage. The chicks are inclined to stagger, showing signs of leg weakness. The feathers are ruffled and the eyes may be gummed up. Mortality is usually high. Post-mortem examination shows the kidneys and ureturs (the tubes which run down the medial side of the kidney lobes to the cloaca) to be filled with a yellowish-white mass of urates.

Mild avitaminosis A in adult birds leads to lowered egg production and susceptibility to colds, coryza, infestation with worms, and coccidiosis. Complete deprivation of vitamin A gives rise to “nutritional roup”, so called from the accumulation of discharges in the nostrils and eyes, causing swelling beneath the eyes. Affected birds cease laying and have a dejected, unthrifty appearance. Examination after death reveals the presence of numerous cream-coloured pustules on the back of the throat and oesophagus.. The kidneys and ureturs are frequently speckled with yellowishwhite deposits of urates.

The danger of vitamin A deficiency occurring in commercial flocks is very real and usually results from one of the following mistakes:— Failure to feed greenfeed or a fortified fish oil.

Insufficiency of greenfeed or poorquality greenfeed. Use of fish oils in insufficient quantity or of oil which has lost its potency or turned rancid because of poor storage. Mixing fish oil with feed too long before feeding. Affected birds may be restored to health rapidly by dosing them with vitamin A-rich oils at double the normal amounts for 2 weeks and then reverting to the usual quantities in the ration.

Vitamin D

Vitamin D is known as the antirachitic (rickets-preventing) or sunshine vitamin. Before the importance of vitamin D was recognised the rearing of chickens without continuous exposure to sunlight was extremely hazardous; as the normal build-up of calcium and phosphorus in the body and bone development depend on an adequate supply of vitamin D. The skin of the bird contains a substance which on exposure to the ultra-violet rays of sunlight' is transformed into vitamin D 3, supplying naturally the bird’s requirements. Periods of cloudy weather deprive chicks of their natural source of the vitamin. Battery-raised or intensively reared chicks are denied exposure to sunlight and require vitamin D supplied in the diet. The fish oils containing vitamins A and D may be used conveniently

VITAMIN DEFICIENCIES IN POULTRY

to supply their requirements for both vitamins. An important point to consider when buying an oil containing vitamin D for use in poultry diets is that there are several types of vitamin D. Vitamin D 3 is the effective one for poultry.* Effects of Vitamin D Deficiency The effects of feeding a vitamin Ddeficient diet usually are fully evident when chicks are 3 to 4 weeks of age. Poor growth and development are the early signs, followed by a tendency to squat on the hocks. The chicks walk with a stiff-legged gait; the beak becomes rubbery and the bones soft and pliable. Normally the birds remain quite bright in appearance despite the onset of rickets. Examination of dead chicks reveals soft bones which fail to crack when bent and a beaded appearance of the ribs caused by enlarged ends. If kept without access to sunlight or vitamin D 3 in the feed, adult birds lay thin-shelled or shell-less eggs, egg production falls, and the birds show weakness of bones, which tend to fracture easily. Hatchability of eggs is also affected. Rickets The disease, rickets affects principally the bones of young growing stock, causing lameness, stiffness, softening of the bones, and beading at the ends of the ribs. Crooked breastbones may also be a form of rickets. Rickets may arise from a deficiency of vitamin D, calcium, or phosphorus; vitamin D deficiency is the most common cause, calcium shortage is a less frequent cause, and lack of phos-

phorus is rare

VITAMIN AND PROTEIN DEFICIENCIES IN POULTRY

Riboflavin Also known as vitamin 8 9 , riboflavin ic, +b _ ornurth nrnmntinff vitamin it ic nresent in good greenfeld milk whev vest and liver Buttermilk skimmed milt’ and whpv nSw. ’are <mnd Surges*of riboflavinFandlre extremely valuable additions to the diet G?od reasonably good sources. Effects of Riboflavin Deficiency Deficiency of riboflavin in chicks’ diet leads to diarrhoea, retarded ® to g e” W mralysis“caS n g Ua th? chicks to sauat P on the hock? with th? tons inward th 11 th th toes euiieu in wax u. Laying stock seldom suffer from riboflavin shortage, but the requirement of breeding stock is twice that of laying birds to maintain good hatchability in the eggs. An abnormal number of dead germs during the second week of incubation is a result of riboflavin deficiency. If laying stock are receiving a reasonable supply of greenfeld g fht S ?equire g ?uTthTr d ’ribJ-flavin-high supplements 6 The needs of chicks and breeding stock, which are about two and a half times and double that of laying birds respectively, are supplied by the use of 6 to 8 per cent, of buttermilk, skimmed milk, or whey powder in the ration. Up to 2 per cent. * S aISO a Use ‘ rui source oi noonavm. Synthetic riboflavin powder may be used as a supplement in the mash, Liquid skimmed milk and buttermilk are widely used as additions to the diet with good results. Water should also be available, and care must be taken to keep the milk containers fresh and clean.

Vitamin E Though deficiency of vitamin E is not common under ordinary conditions, H has been observed in chicks where excessive amounts of cod-liver oil have been used in the ration. The stora^e of feed with cod-liver oil already added for prolonged periods W *’«> give rise to vitamin E deExcessive or rancid fish oil or other fat destroys the vitamin content of the ration - Effects of Vitamin E Deficiency , Affected chicks develop a condition known „?% nutritional encephalomalacia or “crazy chick” disease, The chicks fall over backward or on one side when they attempt to walk, Advanced cases may be prostrate, go into convulsions, or show tremors of the head and neck. j n ducklings deficiency of vitamin e giving rise to nutritional myopathy occurs quite frequently in New Zealand . It results in degeneration and wasting of the muscles in birds 2 to 3 weeks of causing lameness and difficulty in standing upright. Eventuad Y they are unable to S raise their bead j-. The addition of wheat germ to the diet gives spectacular results. Good sources of vitamin E are wheat-germ meal, wheat bran and pollard, cottonseed oil, and grains. PROTEINS AND AMINO ACIDS PROTEINS AND AMINO ACIDS A great variety of proteins exists; in fact, no two foodstuffs contain exactly the same type of protein. Proteins are complex compounds. which consist of a combination of simpler compounds known as amino acids. Of the large number of known amino acids only a limited number are regarded as essential. These essential

amino acids must be supplied in the diet, and absence of one or more leads to loss of weight, reduced food consumption, and infertility. A protein is said to be of good quality for feeding to poultry when it contains most of the amino acids the birds require for normal growth and reproduction, Most plant proteins are inferior to anima! prote&J Powd^. meat good-quality proteins. are examples The term protein as applied to a foodstuff such as meat meal someron?n S in t nrot^n US thf nrotefn Snt varies® w“d%? in dPfferSt materials. Maize, for example, contains about 10 per cent, of protein, wheat bran 15 per cent., skimmedmilk powder 35 per cent., and meat meal of good quality 60 per cent. Because of their high content of protein, skimmed-milk powder and meat meal are referred to as protein foods, a term which is often reduced to “proteins”. Therefore, when meat meal and skimmed-milk powder are described as good-quality proteins, it must be understood that they are foodstuffs which have a high percentage of actual protein of a well-balanced type aming most of the essential ammo aclasi i ■ - d i • r* x i Calculating rrotein Content This aspect must also be borne in S ?number*of"oodstuffl Whin"? from I"number o? foodsSil Wh!n a ration is being composed the percentage of. protein present in each of the ingredients must be ascertained from a food-analysis table, and from these figures must be worked out the amount of each foodstuff to be added to the mash to obtain the required proportion of protein necessary for growth, egg production, and mainten-

NUTRITIONAL DEFICIENCIES IN POULTRY

ance of health. A simple example of one method used may help to clarify this point.

For chicks up to 8 weeks of age the feeding of 18 to 20 per cent, of protein in the ration is recommended. When standard chick mash No. 1, which contains ' about 14 per cent, protein, is used, the addition of a high-protein foodstuff is necessary to supplement the amount of protein and bring the content of the mash up to the desired 18 to 20 per cent. Meat meal and skimmed-milk powder are two of the protein supplements in common use. The food-analysis table shows that meat meal contains 60 per cent, of protein (that is, 1001 b. contains 601 b. of protein) and skimmed-milk powder contains 35 per cent, protein. 1001 b. of standard chick mash No. 1 (14 per cent, protein) supplies 141 b. of protein 101 b. of meat meal (60 per cent, protein) supplies 60 X 10 = 61b. of protein 100 81b. of skimmed-milk powder (35 per cent, protein) supplies 35 X 8 —2.81 b. of protein 100 The total quantity of mash is now 100 + 10 4- 8 —1181 b. containing 14 -4- 6 -J- 2.8 = 22.81 b. of protein Therefore 1001 b. of mash now contains 22.8 X 100 —19.31 b. of protein 118 That means that the supplementary mash contains 19.3 per cent, protein and is suitable for the feeding of chicks from a day old to 8 weeks. Amino acid deficiencies are unlikely to arise under the usual feeding conditions in New Zealand.

Protein Requirements

The value of a poultry ration depends to a considerable extent on its protein content. The normal functions of the body require constant replacement of the protein which is being used up. The protein of the ration is broken down to the simpler amino acids , during digestion; these acids are absorbed from the intestine through the bloodstream and are reconstituted into the type of protein required by the body. Protein is required by poultry for growth, feathering, and egg production. If the protein content of the ration is too low, the rate of growth and feathering is slow. Egg production is directly affected, and laying birds on a protein-deficient diet yield poorly and go into an early moult. Resistance to disease is lowered and cannibalism may break out in the flock. Both quantity and quality of protein are therefore of great importance in the formulation of poultry diets. The protein requirements of different classes of stock vary considerably and, as this article is concerned only with the effects of nutritional deficiencies, the recommended amounts

of proteins will be summarised. They are:— Protein Type of stock requirement (per cent.) Chicks up to 6 weeks old 18 to 20 Growing stock 6 to 24 weeks old .. .. 12 to 15 Laying and breeding stock 15 If a mash-grain ration is being fed to stock requiring, say, 15 per cent, of protein, the mash should contain up to 20 per cent, of protein to allow for the fact that the grain portion of the ration provides only 10 per cent, of protein. Growing stock on good range frequently thrive on the lower percentage of protein (12 per cent.) in the ration, as they pick up insects, earthworms, and slugs, which contain animal protein, in addition to the vegetable protein of the pasture.

FIBRE

A fowl is unable to digest fibre effectively, and the presence of excess fibre in the diet leads to indigestion and crop binding. Fibre is necessary to give bulk to feeding stuffs, but the diet should not contain more than 8 per cent, of crude fibre. Oats, bran, and greenfeed are high in fibre content, and excess feeding of these materials may lead to poor growth and production. The presence of excess fibre in the diet reduces the amount of readily digested carbohydrates (starches). In general, the energy content of the ration is inversely proportional to the amount of fibre in the diet; that is, the higher the fibre content, the lower is the energy value of the diet. There is also evidence to show that excesssively 'fibrous food (including poor, rank pasture) predisposes young stock to coccidiosis.

WATER

The inclusion of the subject of water in an article on the effect of nutritional deficiencies is not out of place. Water is such an essential and integral part of the ration that it is usually taken for granted. It is only necessary to consider a few of the functions which water performs in the body to realise the importance of an adequate supply to birds. Water constitutes up to 75 per cent, of the body weight of a bird and more than 65 per cent, of the weight of an egg. It is required for the process of digestion, assimilation, and absorption of feed. It is essential for the formation of blood and lymph and the removal of waste products. Temperature or body heat is controlled by evaporation of moisture from the body. These are but a few of the requirements of the body metabolism for which water is essential. Poultry will survive without food for a considerable period, but for only a short time without water. Shortage of water for a day or even part of a day results in a fall in egg production and a rise in the mortality rate in adults and chicks. Digestive upsets are also common sequels to an irregular or poor water supply, particularly where dry. mash is being fed.

Therefore, to obtain good results in raising young stock or to keep laying birds in production a regular water supply is of primary importance, and, in view of the role of water in transmitting disease, the water must be clean and fresh. The consumption of water varies with the weather. In hot weather larger amounts are needed, but the approximate quantities drunk daily by 100 birds at different ages are as follows: 1 week, 1 gallon; 2 to 5 weeks, 2 gallons; 6 to 9 weeks, 3 gallons; 10 weeks, 4 gallons; older than 10 weeks, 5 gallons.

DIET MOST IMPORTANT FACTOR Dietary deficiencies, with consequent disease, slow growth, and poor production and hatchability, will result from failure to provide poultry with the essential minerals and vitamins required. . Under New Zealand conditions, if attention is paid to the provision of calcium, phosphorus, salt, and manganese, vitamins A and D and riboflavin, and an adequate percentage of protein, there is little chance of such conditions arising. Though the details of the deficiency diseases and the requirements of the essential elements of the diet have been described only briefly, the information given should suffice to indicate the measures to be taken to ensure that the ration supplied to fowls is adequate and complete. Many factors other than diet must be taken into consideration in running a poultry farm successfully, but nutrition is the most important single environmental factor governing the health of the birds.

Vitamin A potency of oil (international units per gramme) For chickens For layers For breeders All-mash ration Mash and grain ration All-mash ration Mash and grain ration All-mash ration Mash and grain ration OZ. oz. oz. lb. oz. lb. oz. lb. oz. . lb. oz. lb. oz. lb. oz. lb. oz. lb. oz. SOO 9 .14 . 1 (i 2 O 1 4 2 8 1000 7 10J 0 11 1 ' 16 1 0 2 0 2000 ■1 6 0 K 0 12 o 8 1 0 5000 . . | U 1 21 • 0 2J 0 4| 0 31 0 7

AMOUNTS OF OIL OF DIFFERENT POTENCIES PER 100LB. OF MASH TO PROVIDE VITAMIN A REQUIREMENTS OF POULTRY