Health Management of Poultry Layer
Poultry egg and meat are important sources of high quality proteins, minerals and vitamins to balance the human diet. Specially developed breeds of egg type chicken are now available with traits of quick growth and high feed conversion efficiency. Depending on the farm- size,poultry farming can be main source of family income or can provide income and gainful employment to small holder farmers throughout the year. Poultry manure has high fertilizer value and can be used for increasing yield of all crops. In poultry rearing disease is a major factor which causes severe impact on economics of farming. Birds are susceptible to diseases many of which are highly contagious. Therefore, it is advisable to take up utmost care for prevention and control of disease.
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The main sources of disease spread in poultry are wet litter, feed and water, close contact, contaminated equipment, attendants and visitors, air, external parasites, free moving birds, rodents and flies, etc.
General principles for prevention of diseases
Procure the day old chicks, which are free from diseases from reputed hatcheries
Feeds must be tested to ensure that they are free from microbial agents or toxins at periodic intervals.
Storage facilities for feed ingredients/feeds must be managed in a hygienic manner.
Sheds having infected flocks should be served with feed at the end of a delivery day.
Always ensure the supply of clean and potable water. If necessary use appropriate sanitizers.
Periodic inspection of wells, piping and tanks to ensure that water supplied is clean.
An area specific vaccination schedule as recommended by hatchery doctor must be practised with utmost care.
Rodent control programme, where ever necessary, must be adopted by employing mechanical (traps) or chemical techniques along with strict sanitation measures.
After selling each crop from the sheds, thorough cleaning of sheds should be done by removing all fixtures, equipment, litter dust, debris followed by brooming and burning. The rat holder cracks, worn out area should be packed with cement.
Avoid use of litter as manure around the farms.
Well cleaning of sheds and equipment with water and appropriate detergent.
A thorough disinfection of sheds, equipments as well as farm surroundings by formalin spray at recommended concentration.
Foot baths should be always filled with disinfectant.
Vehicles visiting the farms should be thoroughly disinfected by appropriate disinfectant spray.
Personnel working in laying sectors should not be allowed into brooding/growing sector or feed manufacturing facilities. All visitors must be ensured to walk through foot baths.
Disposal of dead birds in hygienic manner either by using incinerator or by pit method is very essential.
What to be done at the time of an out break
Restrict the movement of birds (selling and buying)
Follow strict hygienic measures.
Take help of Veterinarians.
Important diseases of chicken
The dry form of fowl pox is characterized by raised, wart-like lesions on unfeathered areas (head, legs, vent, etc.). In laying hens, infection results in a transient decline in egg production. In the wet form there are canker-like lesions in the mouth, pharynx, larynx, and trachea. The wet form may cause respiratory distress by obstructing the upper air passages.
Treatment – No treatment is available. However, fowl pox is relatively slow-spreading. Thus, it is possible to vaccinate to stop an outbreak.
Prevention – Fowl pox outbreaks in poultry confined to houses can be controlled by spraying to kill mosquitoes. However, if fowl pox is endemic in the area, vaccination is recommended.
Newcastle disease is characterized by a sudden onset of clinical signs which include hoarse chirps (in chicks), watery discharge from nostrils, laboured breathing (gasping), facial swelling, paralysis, trembling, and twisting of the neck (sign of central nervous system involvement). Mortality ranges from 10 to 80 per cent depending on the pathogenicity.
Treatment – There is no specific treatment for Newcastle disease. Antibiotics can be given for 3-5 days to prevent secondary bacterial infections. For chicks, increasing the brooding temperature 5°F may help reduce losses.
Prevention – Prevention programs should include vaccination, good sanitation, and implementation of a comprehensive biosecurity programme.
The severity of infectious bronchitis infection is influenced by the age and immune status of the flock, by environmental conditions, and by the presence of other diseases. Feed and water consumption decline. Affected chickens will be chirping, with a watery discharge from the eyes and nostrils, and laboured breathing with some gasping in young chickens. Breathing noises are more noticeable at night while the birds rest. Egg production drops dramatically. Eggshells become rough and the egg white becomes watery.
Treatment – There is no specific treatment. Antibiotics for 3-5 days may aid in combating secondary bacterial infections. Raise the room temperature 5°F for brooding-age chickens until symptoms subside. Baby chicks can be encouraged to eat by using a warm, moist mash.
Prevention – Establish and enforce a biosecurity program. Vaccines are available.
Avian influenza is categorized as mild or highly pathogenic. The mild form produces listlessness, loss of appetite, respiratory distress, diarrhea, transient drops in egg production. The highly pathogenic form produces facial swelling, blue comb and wattles, and dehydration with respiratory distress. Dark red/white spots develop in the legs and combs of chickens. There can be blood-tinged discharge from the nostrils. Mortality can range from low to near 100 per cent. Sudden exertion adds to the total mortality. Egg production and hatchability decreases. There can be an increase in production of soft-shelled and shell-less eggs.
Treatment – There is no effective treatment. With the mild form of the disease, good husbandry, proper nutrition, and broad spectrum antibiotics may reduce losses from secondary infections. Recovered flocks continue to shed the virus.
Prevention – A vaccination programme used in conjunction with a strict quarantine has been used to control mild forms of the disease. With the more lethal forms, strict quarantine and rapid destruction of all infected flocks remains the only effective method of stopping an avian influenza outbreak. If you suspect you may have Avian Influenza in your flock, even the mild form, you must report it to the state veterinarian’s office.
Chickens 14 weeks and older are more susceptible than young chickens. Most outbreaks occur in mature hens. The clinical sign usually first noticed is watery eyes. Affected birds remain quiet because breathing is difficult. Coughing, sneezing, and shaking of the head to dislodge exudate plugs in the windpipe follow. Birds extend their head and neck to facilitate breathing (commonly referred to as “pump handle respiration”). Inhalation produces a wheezing and gurgling sound. Blood-tinged exudates and serum clots are expelled from the trachea of affected birds. Many birds die from asphyxiation due to a blockage of the trachea when the tracheal plug is freed.
Treatment – Administer antibiotics to control secondary infection, and vaccinate the flock. Vaccination of individual bird by the eye-drop route is suggested. In small poultry flocks, use a swab to remove plug from gasping birds.
Prevention – Vaccinate replacement birds for outbreak farms.
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Birds infected with the synovitis form show lameness, followed by lethargy, reluctance to move, swollen joints, stilted gait, loss of weight, and formation of breast blisters. Birds infected with the respiratory form exhibit respiratory distress. Greenish diarrhea is common in dying birds.
Treatment – Recovery is slow for both respiratory and synovitis forms. The most effective antibiotics are tylosin, erthromycin, spectinomycin, lincomycin, and chlorotectracycline. These treatments are most effective when the antibiotics are injected.
Prevention – Eradication is the best and only sure control
Aspergillosis occurs as an acute disease of young birds and a chronic disease in mature birds. Young birds have trouble breathing and gasp for air. Characteristically, there are no rales or respiratory sounds associated with aspergillosis. Feed consumption decreases. Occasionally there is paralysis or convulsions caused by the fungal toxin. Mortality in young birds averages 5-20 per cent, but may be as high as 50 per cent. Mature birds also have respiratory distress, reduced feed consumption, and may have a bluish and dark colour of the skin (cyanosis). Nervous disorders, such as twisted necks, may occur in a few birds. Mortality in mature birds is usually less than 5 per cent.
Treatment – There is no cure for infected birds. The spread can be controlled by improving ventilation, eliminating the source of the infection, and adding a fungistat (mycostatin, mold curb, sodium or calcium propionate, or gentian violet) to the feed and/or copper sulfate or acidified copper in the drinking water for 3 days. The litter can be sprayed lightly with an oil-base germicide to control dust and air movement of fungal spores.
Prevention – It is important to thoroughly clean and disinfect the brooding area between broods. Use only clean litter, preferably soft wood shavings. Do not use sawdust, litter high in bark content, or shavings that have been wet.
Marek’s disease is a type of avian cancer. Tumours in nerves cause lameness and paralysis. Tumours can occur in the eyes and cause irregularly shaped pupils and blindness. Tumours of the liver, kidney, spleen, gonads, pancreas, proventriculus, lungs, muscles, and skin can cause incoordination, unthriftiness, paleness, weak labored breathing, and enlarged feather follicles. In terminal stages, the birds are emaciated with pale, scaly combs and greenish diarrhea. Marek’s disease is very similar to Lymphoid Leukosis, but Marek’s usually occurs in chickens 12 to 25 weeks of age and Lymphoid Leukosis usually starts at 16 weeks of age.
Treatment – none
Prevention – Chicks can be vaccinated at the hatchery. While the vaccination prevents tumour formation, it does not prevent infection by the virus.
The virus involved has a long incubation period (4 months or longer). As a result, clinical signs are not noticeable until the birds are 16 weeks or older. Affected birds become progressively weaker and emaciated. There is regression of the comb. The abdomen becomes enlarged. Greenish diarrhea develops in terminal stages.
The virus is present in the yolk and egg white of eggs from infected hens. Most national and international layer breeders have eradicated lymphoid leukosis from their flocks.
Infectious Bursal Disease
In affected chickens greater than 3 weeks of age, there is usually a rapid onset of the disease with a sudden drop in feed and water consumption, watery droppings leading to soiling of feathers around the vent, and vent pecking. Feathers appear ruffled. Chicks are listless and sit in a hunched position. Chickens infected when less than 3 weeks of age do not develop clinical disease, but become severely and permanently immunosuppressed.
Treatment – There is no specific treatment. Vitamin- electrolyte therapy is helpful. High levels of tetracyclines are contraindicated because they tie up calcium, thereby producing rickets.
Prevention – Vaccine is commercially available.
Signs commonly appear during the first week of life and between the second and third weeks. Affected chicks may first show a dull expression of the eyes, followed by progressive incoordination, sitting on hocks, tremors of the head and neck, and finally paralysis or prostration. Some may refuse to walk or will walk on their hocks. In advanced cases, many chicks will lie with both feet out to one side (prostrate) and die. All stages (dullness, tremors, prostration) can usually be seen in an affected flock. Feed and water consumption decreases and the birds lose weight. In adult birds, a transitory drop (5-20 per cent) in egg production may be the only clinical sign present. However, in breeding flocks, a corresponding decrease in hatchability is also noted as the virus is egg- transmitted until hens develop immunity. Chickens which survive the clinical disease may develop cataracts later in life.
Treatment – There is no treatment for outbreaks. Infected birds should be removed, killed and incinerated. Recovered chicks are unthrifty.
Prevention – Vaccine is available.
Fowl cholera usually strikes birds older than 6 weeks of age. In acute outbreaks, dead birds may be the first sign. Fever, reduced feed consumption, mucoid discharge from the mouth, ruffled feathers, diarrhea, and laboured breathing may be seen. As the disease progresses birds lose weight, become lame from joint infections, and develop rattling noises from exudate in air passages. As fowl cholera becomes chronic, chickens develop abscessed wattles and swollen joints and foot pads. Caseous exudate may form in the sinuses around the eyes. Turkeys may have twisted necks.
Treatment – A flock can be medicated with a sulfa drug (sulfonamides, especially sulfadimethoxine, sulfaquinonxalene, sulfamethazine, and sulfaquinoxalene) or vaccinated, or both, to stop mortality associated with an outbreak. It must be noted, however, that sulfa drugs are not FDA approved for use in pullets older than 14 weeks or for commercial laying hens. Sulfa drugs leave residues in meat and eggs. Antibiotics can be used, but require higher levels and long term medication to stop the outbreak.
Prevention – On fowl cholera endemic farms, vaccination is advisable. Do not vaccinate for fowl cholera unless you have a problem on the farm. Rodent control is essential to prevent future outbreaks.
Affected chicks may have external navel infection, large unabsorbed yolk sacs, peritonitis with foetid odour, exudates adhering to the navel, oedema of the skin of ventral body area, septicemia and dehydration.
Treatment – There is no specific treatment for omphalitis. Most affected birds die in the first few days of life.
Prevention – Control is by prevention through effective hatchery sanitation, hatchery procedures, breeder flock surveillance, and proper preincubation handling of eggs. Mushy chicks should be culled from the hatch and destroyed.
Death of infected chicks begins at 5-7 days of age and peaks in another 4-5 days. Clinical signs – huddling, droopiness, diarrhoea, weakness, pasted vent, gasping, and chalk-white feces, sometimes stained with green bile. Affected birds are unthrifty and stunted because they do not eat. Survivors become asymptomatic carriers with localized infection in the ovary.
Treatment – Treatment is for flock salvage only. Several sulfonamides, antibiotics, and antibacterials are effective in reducing mortality, but none eradicates the disease from the flock.
Prevention – Pullorum outbreaks are handled, on an eradication basis. Breeder replacement flocks should be tested before onset of production to assure pullorum- free status.
Rapidly growing young birds, especially chickens 2-12 weeks of age, are most susceptible. Initially there is a reduction in feed consumption as well as dark, often blood-stained, faeces. Infected chickens will have diarrhoea. Chronically affected birds become emaciated. The bird, intestines, and faeces emit a faetid odour.
Treatment – The clostridia bacteria involved in necrotic enteritis are sensitive to the antibiotics bacitracin, neomycin, and tetracycline. However, antibiotics such as penicillin, streptomycin, and novobiocin are also effective. Bacitracin is the most commonly used drug for control of necrotic enteritis.
Prevention – Prevention is directed toward sanitation, husbandry and management.
Infections appear in three forms – septicemia (acute), arthritic (chronic) and bumblefoot. The septicaemia form appears similar to fowl cholera in that the birds are listless, without appetite, feverish, and show pain during movement. Black rot may show up in eggs (the organism is passed in the egg). Infected birds pass fetid watery diarrhea. Many will have swollen joints (arthritis) and production drops. The arthritic form follows the acute form. Birds show symptoms of lameness and breast blisters, as well as painful movement. Birds are reluctant to walk, preferring to sit rather than stand. Bumblefoot is a localized chronic infection of the foot, thought to be caused by puncture injuries. The bird becomes lame from swollen foot pads.
Treatment – Novobiocin (350 g/ton) can be given in the feed for 5-7 days. Erythromycin and penicillin can be administered in the water for 3-5 days or in the feed (200 g/ton) for 5 days. Other antibiotics and drugs are only occasionally effective.
Prevention – Remove objects that cause injury. Isolate chronically affected birds. Provide nutritionally balanced feed.
Birds that are fed an adequate diet made up from a good commercial feed are unlikely to suffer from nutritional problems unless there are additional factors involved, such as diseases that result in diarrhoea or otherwise interfering with the digestive system.
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Any form of stress may result in a disease outbreak, or diseases in individual birds, as a result of a disease causing organism that is not normally a problem. Any disease will also result in stress, and may therefore increase the potential for other diseases. Stress may result in the immune system not being able to cope with the disease challenge.
Cannabilism and feather picking
Cannibalism is a problem that is particularly associated with large poultry flocks where birds kept in close confinement peck at each other. This can produce significant mortality in the flock when injury results. It will also cause a decrease in egg production as the hen-pecked birds become stressed. Some chickens are more likely to engage in cannibalism than others. The problem has a range of causes, which are heat without adequate ventilation/nests and nesting areas not dark enough /crowding/ high densities of birds/ boredom or lack of exercise /feed and water troughs too few or too close together/external parasites may cause a chicken to pull out its own feathers, and draw blood. This may attract other birds to peck at the area.
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