Storey's Guide to Raising Chickens (43 page)

It becomes susceptible to other diseases that take significant time to develop.

From a health perspective, the older a breeding chicken gets, the more valuable it becomes, since by its longevity it demonstrates a certain hardiness that’s likely to be inherited by its offspring. From a production standpoint, however, the older a chicken gets the less economical it becomes, with the profit curve dropping ever more sharply as long-term diseases take their toll. For the latter reason many poultry owners won’t keep a chicken more than 1 or 2 years, 3 at the most.

Because commercial producers can’t afford the economic loss resulting from a serious disease, and because mixing birds of different ages increases the likelihood of disease, commercial folks follow the “all in, all out” procedure — they keep a meat or egg flock for the most productive part of its life, then remove the whole flock and thoroughly clean the housing before bringing in another flock. Although the natural life of a chicken is about 12 years — with individuals occasionally living as long as 25 years — rare is the chicken that survives beyond its productive life of about 2 years.

The best way to nip a potential disease problem in the bud is to be constantly aware of your flock’s state of health. Each time you visit your chickens, take a moment to look around. You’ll readily spot problems in the making if you become fully familiar with these characteristics.

Appearance.
Healthy chickens look perky and alert. They have full, waxy combs, shiny feathers, and bright eyes.

Activity.
Healthy chickens are active. They peck, scratch, dust, preen, or meander almost constantly, except on hot days, when they rest in the shade.

Sound.
Well chickens talk and sing throughout the day. To detect atypical sounds, whistle softly whenever you approach your flock. Out of curiosity your chickens will stop their activities to listen, giving you a chance to hear coughs, sneezes, and other sounds of distress. Listening while they are roosting at night is another good time to hear atypical sounds.

Production.
Each flock develops a characteristic laying pattern, based in part on the hens’ breed and age and in part on your management style. Keep records to determine your hens’ average rate of lay, as well as the seasonal variations you can come to expect. Familiarize yourself with the typical sizes and shapes of
your hens’ eggs. An inexplicable decline in production or in egg quality (thin or wrinkled shells, thin whites, and so forth) may be a sign of disease.

Eating and drinking.
The amount of feed and water a chicken consumes each day depends on its age, size, and production level, as well as on the weather. By paying attention to how much your chickens normally eat and drink, you’ll readily notice changes brought on by stress or disease.

Weight.
Healthy young chickens gain weight steadily. Healthy mature chickens hold their weight except for possible slight drops during the breeding season or resulting from the stress of exhibition. Any inexplicable loss of weight or failure to gain can be a danger signal.

Odor.
A healthy flock has a characteristic odor. Become aware of that odor so you can detect subtle changes that may result from an outbreak of respiratory or intestinal disorders.

Droppings.
Chickens expel two different kinds of droppings. Regular intestinal droppings are firm, grayish brown, and capped with white urine salts. Approximately every tenth dropping comes from blind pouches in the intestine, called ceca, where cellulose is digested by fermentation. Cecal droppings tend to be somewhat foamy, smellier than regular droppings, and light brown or sometimes greenish in color. Any change in the normal odor or appearance of either kind of dropping is a pretty good indication of disease.

CAUSES OF DISEASE

Infectious organisms of one sort or another are always in the environment. Many of them don’t cause disease unless a flock is stressed by such things as crowding, unsanitary conditions, or changes in feed. Microscopic organisms are spread through the air, soil, and water, as well as through contact with diseased chickens. They may be carried from flock to flock on the feet, fur, or feathers of other animals, especially rodents and wild birds, and on equipment, human clothing (particularly shoes), and vehicle tires.

The disease most likely to strike a specific group of chickens is influenced by the flock’s purpose. Exhibition birds are most likely to get a respiratory disease such as laryngotracheitis that spreads through the air. Broilers are most likely to experience diseases related to nutrition and rapid growth —
ascites
(fluid accumulation in the abdominal cavity) or leg weaknesses. A breeder flock is more likely to experience a disease requiring long-term development, such as tuberculosis.

Each disease has unique signs by which it may be identified. Each disease also shares some signs with other diseases. Reduced egg production is often the first general sign of any disease, soon accompanied by depression, listlessness, hunching, hanging of the head, dull or ruffled feathers, loss of appetite, and weight loss. Other signs may be grouped according to the body system affected, as detailed below.

Enteric diseases
affect the digestive system and are characterized by loose or bloody droppings, weakness, loss of appetite, increased thirst, dehydration, and weight loss in mature birds or slow growth in young birds. Enteric diseases include campylobacteriosis, canker, coccidiosis, colibacillosis(
E. coli
infection), necrotic enteritis, salmonellosis (typhoid, paratyphoid, pullorum), thrush, ulcerative enteritis, and internal parasites (parasitic worms).

Respiratory diseases
invade a bird’s breathing apparatus and are characterized by labored breathing, coughing, sneezing, sniffling, gasping, and runny eyes and nose. Respiratory diseases include coryza, cholera, chronic respiratory disease, bronchitis, gapeworm, influenza, laryngotracheitis, Newcastle disease, and wet pox.

Nervous disorders
affect the nervous system and are characterized by loss of coordination, trembling, twitching, staggering, circling, neck twisting, convulsions, and paralysis. Typical nervous disorders are botulism and Marek’s disease.

Septicemia
occurs when any infection reaches the bloodstream. Signs include weakness, listlessness, lack of appetite, chills, fever, dark or purplish head, prostration, and death. Many diseases have the ability to become septicemic — most notably cholera, colibacillosis, and streptococcosis (strep infection).

Acute septicemia hits a bird so fast it literally drops in its tracks. Since most septicemic diseases cause reduced appetite and loss of weight before death, the classic indication of acute septicemia is the sudden death of an apparently healthy bird that has a full crop and is in good flesh.

Not all causes of death are septicemic, however. Death may result from, among other things, degeneration of the intestine due to an enteric disease, blocking off of the airways due to a respiratory disease, inability to eat or breathe due to paralysis caused by a nervous disease, lack of adequate feed or water, or poisoning.

Occasionally finding a dead chicken does not necessarily mean some terrible disease is sweeping through your chickens. Normal mortality among chickens is 5 percent per year. If you find several chickens dead within a short time, however, you have good reason for concern.

Avian influenza, or bird flu, is included here not to cause panic (too much of that has gone on already) but to provide information so you can reassure family, friends, and yourself the next time the news media try to stir up a panic. Bird flu has been around for many centuries, during which time numerous strains of the virus have evolved. They are divided into two groups: low pathogenicity and high pathogenicity. The
low-path bird flu
strain is somewhat common in the United States, and in most cases causes minor or no signs in chickens and poses little health threat to humans.

High-path bird flu
is the one reported in the news as affecting chickens in Asia and Eastern Europe, where chickens roam freely and people have extensive, direct contact with their birds. High-path strains spread more rapidly than low-path strains and are more likely to be fatal to chickens. High-path bird flu has been detected in chickens — and eradicated — in the United States three times: in 1924, in 1983, and in 2004. No humans are known to have become ill in connection with these outbreaks.

A virus is defined as “high path” if it kills 6 out of 10 chicks inoculated in the laboratory. The high-path strain most often discussed in the news, H5N1, killed 10 out of 10 inoculated chicks.

If you’re interested in knowing what the numbers and letters mean, this is it: Bird flu viruses are classified by a combination of two groups of proteins, the hemagglutinin, or H proteins, and neuraminidase, or N proteins. The 16 H proteins are identified as H1 through H16, and the nine N proteins are N1 through N9. These two groups combine to form 144 different strains of the bird flu virus, each of which is identified by the two proteins they display. The H5N1 strain has the fifth hemagglutinin and the first neuraminidase.

H5N1 does not normally affect humans, although since 1997, when it first appeared, sporadic human cases of a serious respiratory infection have occurred during bird flu outbreaks, in which people who became infected had extensive, direct contact with sick birds. Although about half of these people died, the total of human deaths worldwide from bird flu since 1997 remains less than three hundred, compared to annual deaths of about five hundred thousand worldwide for your average run-of-the-mill human flu. Many more people who did not get sick after contact with infected chickens developed antibodies to the virus.