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Poultry Diseases - By Saskatchewan Agriculture, Food and Rural Revitilization

by 5m Editor
1 August 2004, at 12:00am

This factsheet discusses some of the general basics of poultry disease management and prevention. Some of the diseases which are common in more than one species will also be discussed.

Poultry Diseases - By Saskatchewan Agriculture, Food and Rural Revitilization - This factsheet discusses some of the general basics of poultry disease management and prevention. Some of the diseases which are common in more than one species will also be discussed.

Disease Prevention and Management

Sanitation
Appropriate sanitation and disinfection measures will help to prevent disease transfer from the old flock to the new one.

One of the key preventative measures for poultry diseases is proper sanitation. It is important to thoroughly clean out the empty rooms between flocks and remove any visible manure and dirt. All feeding, watering, and ventilation equipment should also be scrupulously cleaned.

Following cleaning and prior to placement of new chicks the area should also be sprayed with a good disinfectant. Types of disinfectants include phenols, cresols, hypochlorites, quaternary ammonium compounds, iodophors, and formols. Leaving the building empty for a short period of time (2-3 weeks) will also aid in eliminating infectious organisms. Some diseases (coccidiosis) may not be eliminated, but will be reduced.

If outdoor runs are used, they should also be scraped clean. Disinfection is difficult, but it is beneficial to allow the area to dry thoroughly prior to bird placement. It is also important to keep the area as dry as possible when birds are present.

Isolation
Isolating poultry flocks from other animals reduces the opportunity for disease transmission. Young birds should be isolated from older birds if more than one age group is present on the farm. Steps should also be taken to keep wild birds, rodents, insects and pets away from poultry. Humans can also transmit diseases from pet birds to a poultry flock.

Any dead birds should be removed and disposed of promptly.

Vaccination
If birds are being kept for an extended period of time, it might be appropriate to vaccinate for various infectious diseases. A vaccination introduces an organism, either live or dead, which will stimulate an immune response. If successful, a bird that is later challenged with the disease will be able to resist it.

A local veterinarian or agricultural representative should be consulted for information regarding diseases which may be present in your area. However, all chickens which are to be kept longer than 6 weeks of age should be vaccinated for Marek's disease at the hatchery. Marek's disease is caused by a virus and is characterized by nervous disorders, and tumours in the major internal organs. There is usually a high incidence of death, and condemnations at slaughter.

Good Management

Brooding Good brooding management and adequate placement of feed and water will reduce the number of young birds that die of starvation or dehydration in the first few days. The feed and water must be placed at a level the birds can reach them. Room temperature is important too. Young birds should not be over-heated or chilled during transport and the first few days of brooding. Information on brooding and rearing is available from the Poultry Factsheet No. 1; General Brooding and Rearing.

Air Quality Maintaining good air quality at all times will help to prevent respiratory diseases. This is assisted by proper ventilation of the poultry building, which will remove excess moisture, reduce ammonia levels, and keep down the amount of dust in the air. Fans (or open windows) are needed to provide proper ventilation. High levels of ammonia and dust can damage lung tissue and increase susceptibility to respiratory disease. At approximately 10-15 ppm a person can detect ammonia, and over 20 ppm will cause eyes to water. As it gets stronger, it could adversely affect birds (> 25 ppm).

Nutrition Diets which are balanced and contain adequate nutrients are important in disease prevention. Deficiencies of any of the nutrients can cause disease or make birds more susceptible to infectious and non-infectious disease. Deficiency problems often seen in small flocks include protein, vitamin A, vitamin D, calcium and phosphorus. For further information, consult the Poultry Factsheet No. 2; General Nutrition.

Poison Access Care should be taken to remove or prevent the presence of poisons in the areas where birds have access to them. This includes insecticides and pesticides, anti-freeze (ethylene glycol), lead, and misused medications. Mouldy feeds can also cause problems due to the mycotoxins that are produced by the mould.

Nutritional Diseases

Rickets
Rickets can occur in young birds due to insufficient vitamin D3, calcium and/or phosphorus. Commercial feeds and supplements provide these nutrients, but if they are over-diluted the birds will not get enough. Birds can synthesize their own vitamin D, to a certain extent, with exposure to sunlight.

A deficiency of any of these nutrients can also lead to problems with egg-laying birds. Egg production may be reduced and/or the quality of the egg shell may be poor. In severe cases hens may be afflicted with a disease called cage-layer fatigue (brittle-bone disease, osteoporosis). As indicated by the name, this disease is not usually found in birds raised on the floor.

Vitamin A Deficiency

Vitamin A deficiency is a common nutritional deficiency in small flocks. It shows up in the fall if the birds have only been fed grain and/or allowed to forage. This is because they can obtain vitamin A from greenfeed in the summer, and can store it for a short period of time in the liver. Once the greenfeed is gone however, they become deficient unless they are getting vitamins from another source.

Symptoms include staggering, thinness, paleness and blindness. Blood spots may also be seen in eggs of laying birds. If diagnosed early enough, birds will respond to vitamin supplementation.

Parasites

Coccidiosis
Coccidiosis is a parasitic infection (protozoan) common to birds which have access to their own litter. Once coccidiosis is present on the farm it is difficult to eradicate. Less infection will occur if litter is kept reasonably dry.

The infection can cause a reduction in bird growth or production because the parasite invades intestinal tissue and interferes with nutrient digestion and absorption. Diarrhoea and/or bloody droppings may be seen, depending upon the organism. However, these symptoms may also be related to other diseases. Severe infections can kill birds.

Dietary coccidiostats are often used to prevent or treat this infection when the birds are raised on the floor. They are medications, and caution must be exercised when using them. Medications which are fine for one species may be toxic for another (for example certain coccidiostats will kill dogs and horses). The medication may also be harmful to ducks and geese. Some, but not all medications must be removed from the feed prior to butchering the birds (consult with your feed supplier or veterinarian).

If birds are being kept for an extended period of time, it may be beneficial to gradually induce immunity to coccidiosis. This is especially important for birds being raised for egg production, as the eggs cannot be eaten if the bird is fed anti-coccidial medication or for 3-4 weeks once medication stops. It is also more economical, as medications are costly. The process of inducing immunity begins by using lower strength coccidiostats when the birds are on a starter diet, and then eliminating them altogether. The birds become mildly infected and develop a natural immunity. The birds should be watched carefully once the medication is removed in case a severe infection develops. If symptoms are observed (diarrhoea, droopiness, ruffled feathers, and listlessness), a mild medication can be provided in the water to combat the infection.

Mites
Northern fowl mites are small, black, blood-sucking insects. They don't kill the birds, but can cause a reduction in egg production in laying hens. They don't live long away from the birds, so leaving the chicken house empty between flocks helps to get rid of them. Insecticides can also be used.

Birds can be checked for mites by examining under the wings and in the vent area. Another method is to ruffle feathers over a piece of white paper. Mites falling onto the paper will look like specks of pepper moving about.

Lice
Lice are not as common as mites. They feed on skin follicles and can cause a reduction in production. Egg clusters show up as white spots at the base of wing feather follicles. As with mites, they can be controlled by leaving the house empty or using insecticides.

Cannibalism

Cannibalism occurs when birds peck at the feathers, toes, heads, and vents of other birds. If there is bleeding and further pecking, it may result in the death of the bird. Vent picking occurs often in laying hens and young turkeys. Young hens, especially if they are overweight, are susceptible to prolapse (oviduct does not retract after the egg is laid), which induces pecking in the vent area. It may even lead to the pulling out of the intestines (pick-outs).

There is more than one cause for cannibalism. It occurs more often in egg-type than in meat-type chickens. It may be caused by dietary insufficiencies such as salt, vitamins, or amino acids (protein components). Other factors include stresses such as feed deprivation, over-crowding, over-heating, inadequate ventilation and bright lighting.

Eliminating these stresses can help to prevent or reduce cannibalism. If possible, injured or cannibalised birds should be removed from the flock for a period of time to allow for healing. Leaving them in the flock will provide stimulation for further pecking.

One method to prevent or control cannibalism is by light manipulation. Reducing the light intensity and/or the duration of light in a day should help alleviate cannibalism. The use of red lights is also thought to help in some cases. The length of light exposure each day should not be reduced for laying hens.

An alternative is to trim the beaks on all of the birds, at the hatchery (day old) or later on. The sharp tips (only a very small portion) of the beaks can be removed using nail trimmers or electric beak trimming machines. This will make the beaks less dangerous to the other birds, but will not interfere with eating and drinking.

Metabolic Diseases

Metabolic diseases affect internal body metabolism and development, and are the cause of a large portion of mortality in both commercial and back-yard poultry flocks. The birds of main concern are turkeys and broiler chickens. One of the main factors affecting these diseases is rapid growth rate.

Two of the more important types of metabolic diseases are the cardiopulmonary disorders, sudden death syndrome and ascites. Certain types of leg problems are also related to metabolic disturbances. These metabolic disorders can be reduced significantly by slowing early growth rate. This can be achieved by mild feed restriction. For example, have the feed present only during the daylight period (after the birds are at least one week old). Alternatively, feeds which are less concentrated can be used for a starter diet. This would lower nutrient intake and therefore slow down the initial growth rate. For example, a chick starter for egg laying birds rather than a broiler starter could be used for meat-type chickens. A grower rather than a starter diet could be used for turkeys.

Another method to reduce growth rate is to use lighting programs which have been very successful commercially. These lighting programs reduce the number of hours of light per day that the birds are exposed to (after 5 to 7 days of age). Programs which work well commercially reduce the light from 24 hours/day to 6-8 hours/day, followed by weekly increases. For broiler chickens these increases are approximately 4 hours more light each week, and for turkeys they are approximately 2 hours/week. While these programs are not always practical for raising smaller flocks, even having the lights on only during the natural daylight hours or limiting them to 8-12 hours/day should help reduce the number of dead or crippled birds.

Sudden Death Syndrome (Acute Death Syndrome, Flips, Flipovers)

Chickens and turkeys that die of sudden death syndrome are most often found lying on their backs, although occasionally they are on their fronts. They do not appear to be sick prior to dying, other than convulsions immediately before they die. They are usually large birds and are most often males.

Why the birds die is not well understood, but it is known to be a cardiovascular disorder. In commercial broiler chicken flocks it begins at about 1 week of age and peaks around 3 weeks. Fast growth is a factor, and methods such as those described above will help to slow growth rate and reduce the number dying from this disease.

Ascites (Water-belly) and Heart Failure

Ascites occurs as a result of stress on the cardiopulmonary system and is characterized by a build-up of fluid in the abdomen of the bird. In severe cases, the bird will have a bluish appearance on the combs and feet. Their breathing sounds laboured and gaspy, and they may be crouching and have ruffled feathers. Birds may also die without any obvious symptoms. Birds which do not die from the disease are condemned at the time of slaughter.

There are many factors thought to affect development of ascites. The disease is stimulated by rapid growth, cold temperatures during brooding, high altitudes, excess dietary salt levels and/or genetic factors.

Preventative measures include slowing early growth (described above), making sure that the brooding temperatures are warm enough, and checking water quality (sodium content). It is also important to monitor air conditions in the barn, as dust and ammonia can damage lung tissue and may be a factor in ascites.

Leg Problems (Cripples, Leg Weakness, Lameness)

All birds can be affected by leg problems, but they are seen more often in meat-type birds. The legs may twist at odd angles to the body, or may have an abnormal hock angle (angular deformities) that gives a bow-legged look, or an exaggerated cow-hock appearance. Often the problem gets severe enough that the bird can not move easily to obtain adequate feed or water and slowly wastes away. Other problems can occur in the upper joint of the leg. These birds also appear to have difficulty moving around.

One of the main factors related to the angular deformities seen in broiler chickens and in turkeys is rapid growth early in life. It has been demonstrated many times that by slowing the birds down, either through lighting programs or mild feed restriction, that the number of crippled birds is reduced. Examples of these methods are described in the metabolic disease section.

If the floor of the brooding area is not covered with a good layer of bedding, young birds will slip and slide. This can cause leg problems, especially in young turkeys and waterfowl. It is also important to keep the litter fairly dry, but not dusty. Wet litter can contribute to leg problems and wounds on the feet.

Nutritional deficiencies or imbalances can affect leg development and cause abnormalities. Vitamin or mineral deficiencies (manganese, zinc, selenium, vitamin E, choline, biotin, niacin, folic acid, riboflavin, pyridoxine) can cause the twisted leg appearance or angular deformities in broiler chickens and turkeys. Protein deficiencies or amino acid imbalances can also cause problems.

Microbial infection can also cause leg problems. The joints may or may not be swollen, and the birds resist moving around. Reducing stresses will help to prevent this problem. This can be done by avoiding chilling (especially at night) or crowding the birds, preventing wet litter condition, and practising good preventative disease measures.

References

Agriculture Canada, 1991. Raising chicken and turkey broilers in Canada. Publication 1860/E.

Ontario Ministry of Agriculture and Food, February 1989. Ascites in meat-type chickens caused by right heart failure. Agdex 451/662.

Saskatchewan Agriculture and The University of Saskatchewan, 1987. Guide to Farm Practice in Saskatchewan.

Source: Saskatchewan Agriculture, Food and Rural Revitilization - August 2004