Veterinary · Pre-clinical and foundation · also MSVE LPM-211, MSVE LPM-221, Commercial Poultry Production & Hatchery Management
Commercial broiler and layer production, brooding, lighting, hatchery operation, egg quality and biosecurity for chicken, duck, quail and turkey.
In the exams: ICAR AICE-JRF core group 05; ICAR AIEEA-PG 14 (Poultry Science); China comprehensive paper poultry 20; NAVLE poultry 2%; SAVC Paper 2 poultry 15
Poultry production management is the science and craft of raising domestic birds, mainly chickens but also ducks, turkeys, quail and guinea fowl, for meat and eggs at a profit and to an acceptable standard of welfare and food safety. Poultry is the fastest-growing livestock sector in most of the world because the birds convert feed to food efficiently, reproduce quickly and fit systems from a backyard flock of ten hens to an integrated company placing millions of chicks a week.
For a veterinarian the subject matters in three ways. First, most disease in commercial flocks is a management failure before it is a microbiological one: chilled chicks, wet litter, poor ventilation, broken biosecurity or a vaccine given wrongly. Second, the veterinarian is usually judged on flock numbers such as liveability, feed conversion, egg production and hatchability, so reading and calculating these indices is a daily task. Third, public health, residues and welfare law increasingly decide how birds may be kept, and those rules differ by country.
Worldwide the subject is examined in different ways. Indian postgraduate and PhD entrance papers (ICAR AIEEA-PG Poultry Science, AICE-JRF core group 05, ASRB NET) ask for breeds, physiology of egg formation, incubation periods, hatchery faults, egg quality indices and the standard production formulas. China's national veterinary examination gives poultry a fifth of its comprehensive paper, mostly applied to flock health. NAVLE, SAVC and the Australasian AVE ask fewer but more applied questions: a flock problem, a biosecurity decision or a welfare standard. This manual is written for all of these and says plainly where practice or law varies by country, strain or product.
The domestic chicken (Gallus gallus domesticus) descends mainly from the red junglefowl of South and South-East Asia. It has 78 chromosomes (2n), and the female is the heterogametic sex (ZW), the reverse of mammals, which is the basis of sex-linked chick sexing. The Muscovy duck (Cairina moschata) is a separate species from the mallard-derived common duck; the cross between them, the mule duck, is sterile. Poultry standards group pure breeds into classes by region of development. The American class includes Plymouth Rock, Wyandotte, Rhode Island Red and New Hampshire: dual-purpose, yellow-skinned birds that lay brown-shelled eggs. The Asiatic class includes Brahma, Cochin and Langshan: large, heavy, with feathered shanks and brown eggs, now kept mainly for show. The English class includes Cornish, Orpington, Sussex and Australorp; the Cornish, a heavily muscled game-type bird, supplied the broad breast of the modern broiler. The Mediterranean class includes Leghorn, Minorca and Ancona: light, active, early-maturing birds with white earlobes that lay white eggs and seldom go broody. As a teaching rule, white earlobes go with white shells and red earlobes with tinted or brown shells, but the rule has exceptions.
Every region has native chickens adapted to scavenging, heat and local disease. In South Asia the best-known are the Aseel, a heavy game bird prized for fighting and hardiness but a poor layer; the Kadaknath of western Madhya Pradesh, whose skin, flesh and internal organs are dark because of fibromelanosis (extra melanin in connective tissue); the Chittagong, a tall Malay-type bird of Bangladesh and north-east India; and the Busra of western India. Improved rural varieties developed by crossing native and exotic stock aim to keep hardiness and coloured plumage while raising egg number and growth; they are the backbone of many backyard development programmes. Two single genes from native stock are used in hot climates: the naked-neck gene (Na), which reduces feather cover and improves heat tolerance, and the frizzle gene (F), which curls feathers outward.
Modern commercial chickens are not breeds but hybrids from pedigree lines selected by a small number of international breeding companies. The pyramid runs from pure lines (elite, great-grandparent) to grandparent and parent stock, and finally to the commercial bird, which is a two-, three- or four-way cross. Crossing captures heterosis (hybrid vigour) for fitness traits such as liveability and egg number. Broilers are built on a male line from Cornish-type stock, selected for growth, breast yield and feed conversion, crossed with a female line from White Plymouth Rock type, selected also for reproduction. White-egg layers come from White Leghorn lines; brown-egg layers from Rhode Island Red, New Hampshire, Plymouth Rock and related lines.
Egg-type duck breeds include Khaki Campbell and Indian Runner, which stands upright; meat breeds include White Pekin, Aylesbury and Rouen. Ducks tolerate wet conditions and many common chicken diseases better, forage well in rice fields and lay mostly in the early morning, but they are susceptible to aflatoxin and to duck viral hepatitis and duck plague. The turkey is raised for meat; heavy broad-breasted white strains dominate, and their males are so heavy that commercial breeding depends on artificial insemination. The Beltsville Small White is a smaller type. Japanese quail mature very early, beginning to lay at about six to seven weeks of age, need little floor or cage space and have a short incubation period, which makes them a laboratory model as well as a commercial bird.
Sex-linked genes on the Z chromosome let hatcheries sex chicks by feathers or colour. Because a female receives her only Z from her sire, a sire homozygous for the recessive allele and a dam carrying the dominant allele produce daughters that show the recessive trait and sons that show the dominant one. For feather sexing, a rapid-feathering sire (k k) is mated to a slow-feathering dam (K W): daughters are rapid feathering, with wing primaries clearly longer than the coverts at hatch, and sons are slow feathering. For colour sexing, a gold sire (s s) mated to a silver dam (S W) gives silver sons and gold daughters. Barring works the same way: a non-barred sire and barred dam give barred sons, recognised by a pale head spot at hatch. The recessive sex-linked dwarf gene (dw) reduces body size and is used in some broiler breeder female lines to cut feed cost.
Adult chickens keep a deep body temperature of about 41 °C, higher than mammals. They have no sweat glands, a thick insulating feather coat and, in modern strains, a high metabolic heat output from fast growth or high egg output. They lose heat by radiation and convection from unfeathered areas such as the comb, wattles and shanks, and above all by evaporation from the respiratory tract through panting and, in some species, gular flutter. Panting works only while the air is dry enough to accept moisture, so high humidity makes heat stress worse at any given temperature. Prolonged panting blows off carbon dioxide and causes respiratory alkalosis; the reduced blood bicarbonate lowers the carbonate supply for eggshell, which is why thin shells follow heat waves.
Birds have no teeth. Feed is stored and moistened in the crop, an outpouching of the oesophagus. The proventriculus, or glandular stomach, secretes hydrochloric acid and pepsinogen, and the ventriculus, or gizzard, a thick muscular organ lined with a hard koilin layer, grinds feed, helped by grit or insoluble particles. The small intestine is divided into duodenum, which holds the pancreas in its loop, jejunum and ileum; the yolk-stalk remnant (Meckel's diverticulum) marks roughly the jejunum-ileum junction. Birds have two blind caeca where some microbial fermentation and water reabsorption occur, a short colon and a cloaca, the common chamber for the digestive, urinary and reproductive tracts. Birds excrete nitrogen mainly as uric acid, which forms the white cap on droppings. The bursa of Fabricius, dorsal to the cloaca, is the primary lymphoid organ where B lymphocytes mature; it is the target of infectious bursal disease virus.
The avian lung is small, rigid and does not expand. Air is moved by a system of thin-walled air sacs, usually nine in the chicken (paired cervical, cranial thoracic, caudal thoracic and abdominal sacs, and a single clavicular sac), which act as bellows. Gas exchange takes place in the parabronchi, where air flows in one direction during both inspiration and expiration, making the bird lung more efficient than the mammalian lung. Birds have no muscular diaphragm; they breathe by moving the sternum and ribs, so a bird held tightly on its back or pressed on the keel cannot breathe properly, a point that matters during handling and restraint. Ammonia above about 20–25 parts per million is widely cited as harmful to the respiratory tract and eyes.
In the hen only the left ovary and left oviduct develop and function; the right regresses during embryonic life. The ovary carries a hierarchy of yolk-filled follicles. Yolk precursors are made in the liver under oestrogen and carried in the blood to the follicles. A surge of luteinising hormone triggers ovulation of the largest follicle, usually within about half an hour to an hour after the previous egg is laid. The ovum is caught by the infundibulum, where fertilisation must occur, in about a quarter of an hour. The magnum, the longest section, adds the albumen over about three hours. The isthmus adds the inner and outer shell membranes in a little over an hour. The shell gland, or uterus, holds the egg for about 20 hours, first plumping the albumen with water and salts, then depositing the calcium carbonate shell, the pigment and the cuticle. The vagina passes the egg to the cloaca, and oviposition is driven by arginine vasotocin and prostaglandins. The whole process takes roughly 24 to 26 hours, so a hen lays a little later each day until she skips a day; the run of consecutive eggs is a clutch. Sperm are stored in sperm-host glands at the utero-vaginal junction and fertilise eggs for one to two weeks or more after a mating, longer in turkeys. Broodiness, the maternal behaviour of sitting on eggs, is linked to high prolactin and stops lay; it has been selected almost out of commercial layers but remains strong in native hens and turkeys.
An eggshell is mostly calcium carbonate, about 94 to 95 percent, laid down on an organic matrix. Shell formation happens mainly at night when she is not eating, so calcium comes partly from the gut if feed is still there and partly from medullary bone, a special labile bone laid down inside the long bones under oestrogen shortly before lay begins. This is why layers are fed a high-calcium diet with part of the calcium as coarse particles that stay in the gizzard into the night, and why pullets are switched to a pre-lay diet a little before first egg. When dietary calcium, phosphorus or vitamin D3 are inadequate, structural bone is drained and the hen may develop cage layer fatigue or osteoporosis.
Choose a site with good drainage, water, power and road access, away from other poultry, live-bird markets and water bodies used by wild waterfowl; separation distances are set locally. In hot climates open houses are aligned with the long axis east-west so the sun falls on the roof rather than through the sides. Open-sided or naturally ventilated houses rely on wind and the stack effect, with curtains or shutters on the long sides adjusted by hand or automatically. They are cheap and common in the tropics, but their width must be limited so that cross-ventilation can reach the centre, and bird performance follows the weather. Environmentally controlled houses are closed, insulated and mechanically ventilated. Negative-pressure ventilation with exhaust fans and controlled inlets gives minimum ventilation in cold weather, transitional ventilation, and in hot weather tunnel ventilation, where fans at one end draw air along the house at a speed that produces a wind-chill effect on the birds. Evaporative cooling pads or high-pressure fogging lower the temperature of incoming air, at the cost of higher humidity. Controlled houses allow lighting programmes, higher stocking and more uniform flocks, but depend on power and on alarm and standby generator systems; a fan failure in a closed house can kill a flock within an hour or two.
Most broilers, broiler breeders and turkeys, and many layers, are kept on the floor. In the deep litter system birds live on a bedding layer, commonly 5 to 10 cm of wood shavings, rice husk, chopped straw or similar dry, absorbent, non-toxic material, which is kept dry and friable by ventilation, correct drinker management and stirring. Good litter absorbs moisture from droppings; wet or caked litter raises ammonia, causes foot-pad dermatitis, breast blisters and hock burns, and favours coccidiosis. Slatted or wire floors, alone or combined with litter areas as in the classic breeder house with two-thirds slats and one-third litter, keep birds away from droppings.
Conventional battery cages house small groups of hens on sloping wire floors with feed and water outside and eggs rolling to a collection tray. They give clean eggs, low labour, low parasite and coccidiosis risk and easy control of individual groups, but they severely restrict movement and natural behaviour. The European Union banned conventional cages from 2012 under Council Directive 1999/74/EC, allowing enriched (furnished) cages that give each hen at least 750 cm² of cage area, with a nest, litter for pecking and scratching, perches and claw-shortening devices, and alternative systems. Several other countries, states and food companies have adopted cage-free rules or pledges, while conventional cages remain lawful and common in much of Asia, Africa and Latin America. Alternative systems include barn or single-tier floor systems, multi-tier aviaries, free-range systems with outdoor access and organic systems with further rules on feed, access and stocking. Non-cage systems improve freedom of movement but bring higher risks of feather pecking and cannibalism, floor eggs, keel bone fractures, parasites and, for free-range birds, contact with wild birds carrying avian influenza.
Stocking density is expressed as birds per square metre or, for meat birds, kilograms of live weight per square metre at the end of the growing period. The EU broiler directive 2007/43/EC sets a maximum of 33 kg/m², which member states may allow to rise to 39 kg/m² and then 42 kg/m² when additional conditions on house climate and mortality records are met; in the EU's alternative layer systems the limit is 9 hens per square metre of usable area. Other countries set their own limits, and many have none in law, relying on industry codes. Indian and older textbooks quote floor space per bird for open houses, commonly around 1 square foot per broiler at market and 2 to 2.5 square feet per layer on deep litter; such rules of thumb must be adjusted to bird size, climate and house type. Feeder and drinker space are as important as floor space: every bird must reach feed and water without competition. Drinkers must be set at the correct height so that birds drink without spilling, because spilt water is the commonest cause of wet litter.
Brooding is the care of chicks from placement until they can regulate their own body temperature, usually two to four weeks. A chilled chick eats less, uses its yolk reserve poorly and grows a smaller gut and immune system; early mistakes show later as poor uniformity, mortality and feed conversion. Many broiler guides set a seven-day weight of about four to five times day-old weight as a check. Before chicks arrive, the house is cleaned, disinfected and allowed its downtime; fresh litter is spread; feeders, drinkers and heaters are checked; and the house is preheated long enough that the floor and litter, not only the air, are warm. A cold concrete floor under warm air still chills chicks. For spot brooding, chicks are confined within a brooder guard or chick guard, a circle of board, card or wire around each heat source, which keeps them near heat, feed and water and prevents piling in corners; the guard is widened daily and removed after about a week. Paper or trays with feed are spread over part of the floor, and extra drinkers are provided so that every chick finds water within a short distance.
In spot brooding, chicks can choose a zone within a temperature gradient; in whole-house brooding the entire air space is heated to a uniform temperature. Strain guides typically give a starting temperature at chick level in the low to mid 30s °C for spot brooding, with whole-house air temperatures slightly lower, falling by roughly 2 to 3 °C each week until the house reaches the growing temperature. Relative humidity during the first days is usually kept moderate, around 60 to 70 percent, because dry air dehydrates chicks and raises dust. These are starting points; the chicks themselves are the thermometer.
Chicks that are comfortable are spread evenly, eating, drinking and resting, with a soft background chirping. Chicks that are too cold huddle under or close to the heat source and cry loudly. Chicks that are too hot move away from the heat, pant, droop their wings and crowd near walls. Chicks crowded to one side are usually avoiding a draught or light glare. A useful check is crop fill: a few hours after placement, and again the next morning, feel the crops of a sample of chicks; most should be full and soft, holding both feed and water. A low percentage of full crops means chicks have not found feed or water, or are too cold to eat.
Newly placed chicks are counted and checked for quality: bright eyes, a healed navel, straight legs and a firm, not distended, abdomen. The lighting programme in the first days gives long light periods at good intensity so chicks find feed and water, then introduces darkness. Early mortality in the first week is watched closely; causes include omphalitis (navel infection, often traceable to the hatchery or breeder flock), dehydration, chilling and starve-outs. Beak trimming, the removal of part of the upper beak to reduce feather pecking and cannibalism in layers and turkeys, is done at the hatchery by infrared treatment or on the farm at a young age; it is banned or restricted in some countries on welfare grounds, and where allowed it should be done by trained people at the youngest practical age. Ducklings, poults and quail chicks have their own brooding needs: turkey poults are slow to find feed and water and need extra attention, and ducklings need water deep enough to dip the head but must not be allowed to become soaked and chilled.
A lighting programme manages three things: photoperiod (the number of hours of light in each 24 hours), intensity (brightness at bird level, measured in lux, or in foot-candles in older texts, one foot-candle being about 10.8 lux) and wavelength or colour. Birds see a wider range of wavelengths than people, including ultraviolet, and are sensitive to flicker from some lamps, so what looks adequate to a person may not look the same to a bird. In closed, light-tight houses the programme is fully controlled; in open houses natural daylight sets a minimum and artificial light can only add to it, which limits what can be done. The golden rule for egg-type and breeder birds is simple: never increase day length during rearing and never decrease it during lay. Physiologically, light reaching photoreceptors in the hypothalamus drives release of gonadotrophin-releasing hormone and so of FSH and LH; melatonin from the pineal gland signals darkness.
Old practice was continuous or near-continuous light to maximise feed intake. It is now known that some darkness improves leg health, reduces sudden death and ascites in some settings, improves sleep and welfare, and often does not harm, or even improves, feed conversion. Most programmes give long days for the first few days so chicks find feed, then introduce a dark period, often increasing towards the middle of the growing period and reduced a few days before slaughter. EU Directive 2007/43/EC requires that, from seven days after placement until three days before slaughter, broilers have at least six hours of darkness in every 24 hours, including at least one uninterrupted period of at least four hours. Intermittent programmes that break the day into repeated light and dark blocks are also used. Low intensity in the growing period reduces activity and aggression, but must remain high enough for inspection and welfare.
Pullets are reared on a constant or decreasing day length so that the reproductive system does not develop before the body is ready. In light-tight rearing houses a short day, often around eight to ten hours, is held after the first weeks. At the planned age and body weight, which the strain guide specifies, the pullet is photostimulated by increasing day length in one or more steps. Light stimulation of an underweight pullet gives small eggs, prolapse and poor persistence; stimulation too late wastes feed. Day length is increased stepwise, commonly to around 16 hours at peak, and then held constant for the rest of lay. Pullets reared in open houses under a naturally increasing day length may come into lay early; growers either choose hatch dates to suit the season or rear in dark-out houses and then transfer to open laying houses, where the day length at transfer must not be lower than in rearing.
Turkey breeders become photorefractory, meaning that after a long period on long days they stop responding. Turkey breeder hens are therefore held on short days before being photostimulated, and a period of short days is needed to restore sensitivity. Broiler breeder hens are typically also reared on short days in dark-out houses, which is one reason they are raised in closed rearing facilities even in hot countries. Light intensity is usually kept higher at the start of lay than in rearing, but very bright light in layer houses can increase pecking and cannibalism.
A broiler is a young chicken of either sex raised for meat and slaughtered while still tender. Growth in modern strains is very fast: typical market weights of about 2 to 3 kg are reached in roughly five to seven weeks, depending on strain, sex, nutrition, climate and the market's preferred size. Feed is the largest single cost. Broilers are fed in phases, commonly a pre-starter or starter, a grower and a finisher, with a withdrawal feed free of medicines needing withdrawal periods at the end where such products are used. Diets move from high protein and amino acid density early to higher energy later; typical textbook ranges are around 21 to 23 percent crude protein in the starter falling to 18 to 20 percent in the finisher, with metabolisable energy rising from about 2,900–3,000 to 3,100–3,200 kcal/kg, but modern formulation uses digestible amino acids and national or company nutrient standards, and figures vary. Water intake is usually around 1.6 to 2 times feed intake by weight at moderate temperatures and rises steeply in heat, so water supply, quality and a falling water meter reading are early warnings.
Feed conversion ratio (FCR) is kilograms of feed used per kilogram of live weight produced; lower is better. Liveability is the percentage of placed chicks alive at the end. Because these interact, integrators combine them into the European Production Efficiency Factor (EPEF), also called the European Broiler Index: EPEF = (liveability % × average live weight in kg) ÷ (age in days × FCR) × 100. A flock with 95 percent liveability, 2.4 kg live weight at 40 days and FCR 1.65 scores about 345. Higher is better, and scores cannot be compared fairly between flocks sold at very different ages. Feed cost per kilogram of live weight equals FCR multiplied by the price of feed per kilogram. Corrected FCR adjusts to a standard body weight because heavier birds naturally have higher FCR.
Fast growth brings metabolic disorders. Ascites, or pulmonary hypertension syndrome, is fluid accumulation in the abdomen from right heart failure when oxygen demand exceeds the capacity of the lungs; it is worse at high altitude, in cold, poorly ventilated houses and in fast-growing males. Sudden death syndrome, or flip-over, kills well-grown birds that are found on their backs. Leg disorders include tibial dyschondroplasia, valgus-varus deformity and bacterial chondronecrosis. Controlling early growth by light or feed and good ventilation reduces these. Foot-pad dermatitis is used as a welfare indicator at slaughter in several countries. Heat stress kills heavy broilers in the last week; responses are to increase air speed, use evaporative cooling, avoid feeding in the hottest hours, supply cool water and, where lawful, electrolytes. Catching and transport should be calm, at night or in low light, with feed withdrawn several hours before slaughter to empty the gut and reduce carcass contamination, while water stays available until catching.
Broiler parent stock carry the same genes for appetite and growth as their offspring, and fed to appetite they become obese, lay poorly and suffer leg and heart problems. They are therefore reared on strict feed restriction to follow a target body-weight curve, by controlled daily allowance or, in some countries, skip-a-day programmes, which are restricted in parts of Europe on welfare grounds. Uniformity, the percentage of birds within 10 percent of the flock mean weight, is a key measure; many guides aim for 80 percent or more. Males and females are fed separately in lay, the males from feeders the females cannot reach and the females from grilled feeders that exclude the males' larger heads. The farm itself is run all-in, all-out: one age of birds, placed together and removed together, followed by cleaning, disinfection and a downtime before the next flock.
A laying hen's lifetime output is decided largely during rearing. The pullet must reach the strain's target body weight and frame size at each age, and flock uniformity should be high, because a flock that is uneven at point of lay contains birds that come into lay too early or too late. Pullets are weighed individually in weekly samples from the first weeks. Feed is changed from chick starter to grower and developer diets on body weight rather than only age. Vaccination, beak treatment where lawful, and transfer to the laying house are completed before the onset of lay, ideally some weeks before the first egg, so that birds settle. A pre-lay diet with extra calcium is given for a short period before first egg to build medullary bone.
Modern hybrids typically begin to lay at about 18 to 20 weeks, reach 50 percent production within a few weeks, and peak above 90 percent hen-day production a few weeks later. After peak, production declines slowly while egg weight rises and shell quality falls. Hen-day egg production is the number of eggs laid in a period divided by the total hen-days in that period, the sum of hens alive on each day, times 100; it measures the laying rate of the birds actually present. Hen-housed egg production divides total eggs by the number of hens housed at the start of lay, and so is lowered by mortality and culling; it measures the performance of the investment. Egg mass, the number of eggs times average egg weight, and feed per dozen eggs or per kilogram of egg mass are the efficiency measures. A sudden fall in production or a change in shell colour or quality is an early sign of disease, stress, feed error or water failure.
Layers need moderate energy, adequate balanced amino acids, especially methionine, and a high calcium supply. Typical layer diets contain around 16 to 18 percent crude protein and around 3.5 to 4.5 percent calcium, much higher than the roughly 1 percent in grower feed, with the exact figure set by intake, age and national standards. Part of the calcium is given as coarse limestone or shell grit, which dissolves slowly overnight. Available phosphorus is kept adequate but not excessive, because too much phosphorus hampers mobilisation of bone calcium. Vitamin D3 is essential for calcium absorption. Feed intake falls in hot weather, so nutrient density is raised when intake drops. Yolk colour depends on dietary xanthophylls from yellow maize, green feed or permitted pigment sources; white maize, sorghum or wheat diets give pale yolks.
In floor flocks and backyard or smallholder settings, non-laying hens are identified and culled to save feed. A laying hen has a large, red, waxy comb and wattles; a moist, oval, enlarged vent; pubic bones thin and spread, often about three fingers wide; and a soft, deep abdomen. A non-layer has a shrunken, pale, dry comb, a small puckered dry vent and pubic bones close together. In yellow-skinned breeds, pigment is withdrawn from the body in a fixed order as the hen lays because the xanthophylls go to the yolk: first the vent, then the eye ring, earlobe, beak and finally the shanks; pigment returns in the same order when lay stops. A hen with bleached shanks has therefore been laying for a long time.
Forced or induced moulting brings the whole flock out of lay together, rests the reproductive tract and gives a second cycle with better shell quality and persistence. The old method of full feed withdrawal is prohibited or discouraged in many countries on welfare grounds; non-fasting methods use low-energy, low-sodium or high-fibre diets with reduced light. Common layer problems include cage layer fatigue, a paralysis from depletion of structural bone in high-producing caged hens; fatty liver haemorrhagic syndrome, sudden death from liver haemorrhage in over-conditioned hens, often in hot weather; prolapse of the oviduct, often in over-fat or undersized young layers; feather pecking and cannibalism, driven by genetics, light, diet, lack of foraging material and crowding; and red mites in all systems.
Hatchability starts in the breeder house. Eggs are collected several times a day from clean nests, and only clean, normal-shaped, crack-free eggs of the right size are set. Very small eggs from young flocks and very large or double-yolked eggs hatch poorly. Floor eggs and dirty eggs carry more bacteria and are either set separately or discarded; washing hatching eggs is generally discouraged unless done with a validated method. Eggs are cooled below physiological zero, the temperature below which embryo development effectively stops, usually quoted in the low-to-mid 20s °C. They are stored cool and moderately humid, commonly around 15 to 18 °C for short storage and cooler for longer storage, with high relative humidity, and ideally set within about a week; hatchability and chick quality fall with each extra day of storage. Eggs are warmed gradually to room temperature before setting to avoid condensation, called sweating, on the shell.
Artificial incubation reproduces what a broody hen provides: temperature, humidity, ventilation and turning. In forced-draught incubators, where fans move air across the eggs, chicken eggs are commonly incubated at about 37.5 to 37.8 °C air temperature in the setter, the exact figure depending on the machine, and relative humidity around 50 to 60 percent. The hatcher runs at a slightly lower temperature and a higher humidity, around 65 to 75 percent at hatch, to keep the membranes soft. Eggs lose water through the shell during incubation, and the target is commonly a loss of about 11 to 13 percent of set weight by transfer; the humidity setting is adjusted to reach it. Turning, usually hourly through about 45 degrees each side of vertical, stops the embryo sticking to the shell membrane and helps the membranes develop; it is stopped at transfer. Ventilation supplies oxygen and removes carbon dioxide and heat; late embryos produce considerable heat, which multi-stage machines use and single-stage machines must remove.
Incubation periods are a classic examination fact. The chicken takes 21 days, turkey and common duck about 28 days, Muscovy duck about 35 days, Japanese quail about 17 to 18 days, guinea fowl about 26 to 28 days and geese about 28 to 33 days depending on breed; pigeons take about 17 to 18 days. In the chicken the blastoderm begins development in the hen's body and pauses after laying. During incubation the heart begins to beat by the second day; blood vessels spreading over the yolk are visible by candling within the first week; feathers, beak and claws form in the second week; the embryo turns to its hatching position with its head under the right wing towards the air cell in the third week; transfer to the hatcher is made at about 18 days, when turning stops. The chick draws the yolk sac into its abdomen, pips through the membrane into the air cell (internal pipping) and begins breathing air, then pips the shell (external pipping) and hatches at about 21 days.
Candling means examining eggs against a bright light in a dark room to see their contents. In incubation, eggs are candled at about 5 to 7 days for white-shelled eggs, somewhat later for brown shells, and often again at transfer. A fertile, living egg shows a spider-like network of blood vessels with a dark embryo spot. An infertile egg is clear apart from the yolk shadow. An egg with a blood ring, a red ring across the egg, contains an embryo that died early. At transfer a living egg is dark with a clear air cell. Clear eggs removed from the setter should be broken out to separate true infertiles from very early deaths, because the causes differ: infertility points to the breeder flock (male condition, mating ratio, age, nutrition, disease), whereas early embryo death points to egg handling, storage, fumigation or early incubation conditions.
Fertility is the percentage of eggs set that are fertile. Hatchability can be expressed on total eggs set, which reflects both fertility and embryo survival, or on fertile eggs set (hatch of fertile), which isolates incubation and embryo performance. These three are linked: hatch of total equals fertility times hatch of fertile. A hatch residue breakout, in which unhatched eggs are opened and classified as infertile, early, middle or late dead, pipped dead, cracked, contaminated or malpositioned, is the main diagnostic tool. Patterns suggest causes. Temperature too high gives an early hatch, small and dehydrated chicks, red hocks and more late deaths; too low gives a late, extended hatch with large, soft-bodied chicks. Humidity too low gives small, sticky, dehydrated chicks; too high gives mushy, wet, heavy chicks with unhealed navels. Poor turning gives early deaths and malpositions. Rotten and exploding eggs point to contamination from dirty or floor eggs. Nutritional deficiencies in the breeder diet also appear in embryos; riboflavin deficiency, for example, produces clubbed down.
A hatchery is designed on a one-way flow principle: clean material moves forward and never crosses dirty material. Eggs arrive at a receiving area, are graded, sanitised and placed on setter trays, go to a cool egg-storage room, then to the setter hall, then after transfer to the hatcher rooms, and finally to the chick-processing and dispatch area, which is the dirtiest part because of fluff, shells and debris. Waste leaves by its own route. Air flow follows the same principle: clean zones are kept at positive pressure relative to dirty zones, and each room has its own ventilation. Staff move from clean to dirty areas, not back, and the hatchery is fenced, with shower-in or change facilities and control of vehicles.
In multi-stage incubation, eggs of different ages are in the same setter, and the heat from older embryos warms the younger ones; it is energy-efficient but conditions cannot be tailored to one age. In single-stage incubation, all eggs in a machine are the same age, so temperature, humidity, ventilation and carbon dioxide can be changed day by day to match the embryo's needs, and the machine is cleaned between batches, which helps hygiene. Many hatcheries have moved to single-stage machines. Hatcheries were traditionally fumigated with formaldehyde gas generated by adding formalin to potassium permanganate, in a fixed ratio of about 1 g of permanganate to 2 mL of formalin, with the amount per unit volume scaled to the task. Formaldehyde is an effective disinfectant but is irritant and classified as a human carcinogen, and its use is restricted or banned in some countries; it must never be used on eggs between about 24 and 96 hours of incubation, when embryos are especially sensitive, and it must be neutralised before chicks are exposed. Alternatives include hydrogen peroxide or peracetic acid fogging, ultraviolet treatment and quaternary ammonium or other approved disinfectants.
At pull, chicks are removed from the hatcher and separated from shells and unhatched eggs. They are graded: a first-grade chick is alert, dry, fluffy, with bright eyes, a closed and clean navel, straight legs and toes and no deformities. Culls are humanely killed by an approved method. Sexing may be done by vent examination, a skilled method developed in Japan in which the rudimentary copulatory organ in the cloaca is identified; by feather sexing; or by colour sexing in autosexing crosses. Male chicks of layer strains have little commercial value, and their killing at hatch is an ethical issue; some countries now require or encourage in-ovo sex determination or rearing of males. Chicks are vaccinated at the hatchery as required, for example against Marek's disease, which is given at day-old by subcutaneous or intramuscular injection or in ovo at about 18 days of incubation, and sometimes against infectious bronchitis and Newcastle disease by coarse spray. Chicks should be placed on farm within hours, because delay uses yolk reserves, and they overheat in packed boxes more easily than they chill. Hatchery records per breeder flock and setting (eggs set, fertility, hatch, culls, breakout, vaccines, dispatch) let problems and notifiable-disease contacts be traced.
A chicken egg consists of shell, membranes, albumen and yolk. By weight the shell is roughly a tenth, the albumen roughly 60 percent and the yolk roughly 30 percent, with the exact proportions varying with hen age, strain and egg size; larger eggs carry proportionally more albumen. The shell is a porous layer of calcium carbonate crystals, with thousands of pores for gas exchange, covered by a thin proteinaceous cuticle that closes the pores against bacteria. Beneath it lie the outer and inner shell membranes, which separate at the blunt end after laying to form the air cell as the contents cool and contract. The albumen has thick and thin layers and the chalazae, twisted strands that hold the yolk centred. The yolk is surrounded by the vitelline membrane and carries the germinal disc. Duck eggs are larger, with a proportionally larger yolk and thicker shell, and are used for salted and preserved eggs in East and South-East Asia; quail eggs weigh roughly 10 to 12 g.
External quality covers cleanliness, shell soundness, shape, texture, colour and size. Shell strength depends on thickness and structure; it is measured directly by breaking strength or thickness gauges, or indirectly by specific gravity, floating eggs in salt solutions of increasing density. Shell quality falls with hen age, heat stress, poor calcium or vitamin D3 nutrition, some diseases such as infectious bronchitis and egg drop syndrome, and some mycotoxins. Brown shell colour comes from protoporphyrin deposited in the shell gland in the last hours of shell formation; blue shells in some breeds come from biliverdin. Shell colour has no effect on nutritional value. The shape index is width divided by length times 100; a normal chicken egg is roughly in the low to mid 70s, and abnormal shapes crack more easily in grading and transport.
Internal quality is judged by the height of the thick albumen, the condition of the yolk and the absence of defects. The Haugh unit, the standard measure of albumen quality, is HU = 100 × log10(H − 1.7 W^0.37 + 7.57), where H is the height of the thick albumen in millimetres and W the egg weight in grams. Fresh eggs from young hens score high; the value falls with storage, especially at warm temperatures, and with hen age. In the United States standard, Haugh unit values of 72 or above correspond to grade AA, 60 to 72 to grade A and below 60 to grade B. The yolk index, yolk height divided by yolk width, falls as the vitelline membrane weakens and the yolk flattens. Air cell depth increases with age as water is lost, and is used in grading: EU Class A eggs must have an air space not exceeding 6 mm, and those marked extra not exceeding 4 mm. Blood spots come from small ruptured vessels in the follicle or oviduct; meat spots are bits of tissue or altered blood.
Grading systems differ by country. In the EU, Class A eggs are sold fresh to consumers and must not be washed or cleaned, because washing can damage the cuticle; eggs are also sorted by weight into S (under 53 g), M (53 to under 63 g), L (63 to under 73 g) and XL (73 g and over), and each egg carries a code showing the production system, country and farm. In the United States, eggs for grading must be washed under controlled conditions and then kept refrigerated, and sizing uses weight per dozen. Eggs lose quality through water loss, carbon dioxide loss that raises albumen pH and thins it, and bacterial penetration. Cool storage, stable temperature to avoid condensation, and short marketing chains preserve quality. Salmonella Enteritidis can infect the egg contents through the hen's reproductive tract, which is why vaccination and control programmes in breeder and layer flocks and cold chains are central to egg safety.
Biosecurity is the set of measures that keep infectious agents out of a flock (bio-exclusion), stop them spreading within a site and stop them leaving (bio-containment). It works at three levels: conceptual (siting), structural (fences, bird-proof and rodent-proof buildings, change rooms, carcass disposal) and operational (daily routines), and the operational level costs least but fails most, because it depends on people. Disease enters with birds (chicks, replacement pullets, spent hens moved between farms), with people (staff, visitors, catching crews, vaccination teams, veterinarians), with vehicles and equipment (feed trucks, egg trays, crates), with feed and water, and with wild birds, rodents, insects and other animals. Controls follow the routes. Buy chicks only from known, disease-monitored sources. Keep one age per farm where possible. Allow entry only to essential people, who shower or at least change into farm clothes and boots, wash and disinfect hands, and record their visit; many companies require a period since the last poultry contact. Keep vehicles outside the perimeter or clean and disinfect them. Use dedicated equipment for each house. Treat drinking water and store feed so wild birds and rodents cannot reach it. Footbaths help only if the disinfectant is renewed and boots are cleaned of organic matter first, since most disinfectants are inactivated by organic material.
Between flocks the house is emptied of birds, litter and feed; dry cleaning removes organic matter; the house is soaked and washed with detergent; it is rinsed and dried; an approved disinfectant is applied at the correct concentration and contact time; the water system is flushed and sanitised; and the house is left empty for a downtime before restocking. Disinfectant classes include phenolics, quaternary ammonium compounds, oxidising agents such as peroxygen compounds, aldehydes and chlorine or iodine compounds; each has a different spectrum, sensitivity to organic matter and safety profile, and some are poorly effective against non-enveloped viruses or coccidial oocysts. Success is checked by swabs taken after disinfection.
Vaccination reduces disease and losses; it does not replace biosecurity, and a vaccinated bird may still be infected and shed some agents. Live vaccines, attenuated or naturally mild strains, multiply in the bird, give local and systemic immunity and can be given by mass routes, but must be kept cold, handled carefully and not mixed with disinfectants. Inactivated or killed vaccines, usually oil-emulsion, must be injected individually, give strong, long-lasting antibody and are used for layers and breeders before lay, often after live priming. Routes include drinking water, coarse or fine spray, eye or nasal drop, beak dipping, wing-web stab (used for fowl pox), subcutaneous or intramuscular injection, and in ovo. For water vaccination, chlorine-free water is used, a stabiliser such as skimmed milk powder is commonly added, birds are made mildly thirsty so the vaccine is consumed within about one to two hours, and there must be enough drinker space for every bird. Maternal antibodies from the hen protect chicks early but also neutralise live vaccines given too soon; for infectious bursal disease the vaccination date is often estimated from maternal antibody titres in day-old chicks.
There is no single correct vaccination schedule. Programmes depend on local disease challenge, bird type and lifespan, maternal immunity, national law and available vaccines, and they are drawn up by the flock veterinarian and vaccine suppliers; any schedule in a textbook is an example only. Common targets include Marek's disease, Newcastle disease, infectious bronchitis, infectious bursal disease, fowl pox, avian encephalomyelitis and egg drop syndrome in breeders and layers, and in some countries Salmonella, coccidiosis (by live vaccines) and, where authorised, avian influenza. Serological monitoring by ELISA or haemagglutination-inhibition tests checks whether vaccination has worked and flags field challenge. Highly pathogenic avian influenza and virulent Newcastle disease are listed by the World Organisation for Animal Health (WOAH) and are notifiable in most countries; suspected cases must be reported to the veterinary authority, and control may involve culling, movement restriction and zoning. Many countries run national Salmonella and Mycoplasma control and certification programmes for breeding flocks. Any medicine used in food-producing birds requires observation of the labelled withdrawal period for meat and eggs, and some antimicrobials are prohibited in food animals in some countries — confirm against the product label and your national formulary.
Every flock needs records of placement, daily mortality with causes, feed and water use, weights, egg production, vaccines and medicines with withdrawal dates, and sales. They yield the key indices, are a legal traceability requirement in many countries, and are the first thing a veterinarian asks for in an investigation. The cost of producing a kilogram of broiler or a dozen eggs is built from variable costs (chicks or pullets, feed, vaccines and medicines, litter, energy, labour, transport) and fixed costs (depreciation of buildings and equipment, interest, insurance, land). Feed is usually well over half of total cost, often quoted at 60 to 75 percent, which is why feed conversion and feed price dominate profit. Feed cost per kilogram of live weight equals FCR times feed price; a small improvement in FCR across millions of birds is worth a great deal. For layers, the cost of the pullet is spread over the eggs she lays, and the value of the spent hen is credited at the end. Break-even price is total cost divided by output. Poultry industries range from backyard flocks through independent commercial farms to vertically integrated companies that own breeder farms, hatcheries, feed mills, contract growers, processing plants and distribution. Contract farming spreads risk: the grower provides land, housing and labour, the integrator the birds, feed and technical service, and payment follows performance. Marketing channels include live-bird markets, wet markets, wholesalers, processed-meat distributors, supermarkets and food service. Egg marketing depends on grading, packing and cold chain. Labelling claims are regulated differently in each country.
Processing converts live birds into safe meat. Birds are caught, transported and held with minimal stress, and feed is withdrawn several hours before slaughter so that the gut is empty. At the plant they are unloaded, stunned by an electrical water bath or by controlled atmosphere gas, or slaughtered by a religious method where law permits, then bled by neck cut. Carcasses are scalded to loosen feathers: soft or semi-scald at lower temperatures, around the low 50s °C, keeps the skin's yellow outer layer and suits fresh chilled broilers, while hard scald at higher temperatures, around 60 °C or more, is used for waterfowl and some markets. Evisceration removes the viscera for inspection. Carcasses are chilled rapidly, commonly to 4 °C or below, by water immersion, air chilling or spray, and are then sold whole, portioned, deboned or further processed. Dressing percentage, carcass weight as a percentage of live weight, is typically around 70 to 75 percent for broilers, depending on how it is defined and whether giblets are included.
Eggs that are cracked, undersized or surplus become egg products. After breaking and separation, liquid whole egg, yolk and white are pasteurised; in the United States, for example, liquid whole egg is commonly pasteurised at 60 °C for 3.5 minutes, and other countries set their own time-temperature standards. Products are sold chilled, frozen or dried as powder for bakeries and food manufacturers. By-products include poultry manure and litter, valuable as fertiliser but also a source of ammonia, nitrate and pathogens if mishandled; hatchery waste; feathers, which are processed by hydrolysis into feather meal; and blood and offal meals where law permits their use in feed. Dead birds must be disposed of by approved methods such as rendering, incineration, composting or burial, depending on national rules and disease status.
Learn the numbers that recur in every exam and every farm visit: incubation periods, oviduct times, the hen-day, hen-housed, FCR, EPEF and hatchability formulas, the Haugh unit equation and the lighting rules. Practise calculating them by hand from a set of farm records until you can do it quickly and explain each input. On farm visits during your course, walk a broiler house at placement and at depletion and a layer house at peak; check chick behaviour, crop fill, litter, drinker height and air quality yourself. Break out a tray of unhatched eggs at least once. Link each management fact to physiology, for example heat stress to shell quality, so that you can reason through unfamiliar questions.
Your daily work is flock visits and problem solving. Start every investigation with records: mortality pattern, feed and water intake, weights and production against the strain guide. Walk the house before handling birds; check temperature, ventilation, litter, lighting and equipment. Many 'disease' calls are chilling, water failure or a feed error. Plan vaccination programmes with the client for local challenge and check them by serology and by watching vaccine administration. Audit biosecurity at each visit and write down the gaps. In hatcheries, read breakout results and chick-quality scores with the manager each week. Keep withdrawal periods and residue rules in front of every treatment decision, and report notifiable disease suspicions at once.
At this stage you design systems rather than treat flocks. You advise on house design and ventilation for the local climate, choose strains and write company management standards, and set biosecurity and vaccination policy across many farms and hatcheries. You read performance across hundreds of flocks and find the outliers, using EPEF, feed cost per kilogram and hatchability trends to direct attention. You negotiate with integrators, retailers and regulators on welfare standards such as stocking density, cage-free transitions and beak treatment, and you plan contingency for avian influenza, including zoning, movement control and depopulation. You train farm managers and young veterinarians, and you judge investment decisions on cost of production and risk, not only on biology.
Research questions sit where genetics, physiology, environment and welfare meet: the metabolic cost of rapid growth and its link to ascites and leg disorders, early-life programming through incubation temperature and feeding, in-ovo sex determination, gut health without antimicrobial growth promoters, shell quality in long laying cycles, and welfare outcomes in non-cage systems. You design trials with correct experimental units (the pen or house, not the bird), power them for real farm variation, and analyse production indices properly. You evaluate evidence for policy on stocking density, lighting and moulting, advise international bodies, and supervise students. Your credibility depends on separating strain-guide targets and industry claims from independently replicated findings.
This manual gives principles and textbook ranges, not a strain's targets; body-weight curves, feed allowances, lighting steps and incubator set-points must come from the breeder's current guide for the strain in use. It does not give a vaccination schedule, drug doses or withdrawal periods, because these depend on local disease, national law and product labels. Poultry diseases themselves (Newcastle disease, avian influenza, Marek's, coccidiosis, mycotoxicosis) are covered only as they touch management; their pathology and control belong to the disease subjects. Feed formulation and nutrient requirements are summarised only; see applied non-ruminant nutrition. National space allowances outside the EU, Indian BIS feed and egg standards, detailed geese, emu, ostrich and pigeon production, and processing-plant engineering are not yet covered.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions. Every numerical answer was computed by script and the working is shown in the explanation.
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