What To Look For And When To Make Your Observations
And Tentative Identification Before Losses Are Serious
by Glyde A. Marsh, DVM
Extension Specialist
Ohio State University
Columbus, OH 43210

        Early recognition of disease is necessary for successful poultry management. It permits an immediate response, often before the disease is well established. In most cases, it permits more effective medication and treatment at less cost. In addition to the savings resulting from less medication, quick treatment can be of economic importance in reducing growth and production losses.

        On-the-farm identification of poultry diseases is not always possible. Some diseases can only be identified by laboratory procedures. Many are so complex that not all laboratories are adequately equipped for their study. Laboratory techniques are expensive and time consuming. Their success is very dependent upon how well the birds submitted for examination represent the entire flock.


        Most diseases of poultry can be identified on the farm, at least on a tentative basis. Laboratory findings can serve to confirm or deny a tentative identification. They should be employed as a second step to immediate efforts made on the farm to identify the problem.

        The skilled poultryman should become familiar with the techniques of disease recognition. He must also recognize the hazard attached to over reliance on his own ability.


        Mistakes in diagnosis can be costly. The efficient poultryman learns to employ his skill to the level of his competence, then seeks assistance from his serviceman, veterinarian, or state diagnostic laboratory for those problems he finds too difficult.

        When disease is suspected, the first step should be careful observation of the flock. With a little practice, it is possible to differentiate between normal and sick poultry by such observation.

        For success, the birds should be viewed in their normal environment and before they are subjected to any disturbance. Good practice is to enter the pen or cage area and then stand motionless. In several minutes, the birds will return to their original pattern of activity.

        After an initial observation of the flock, representative individuals can be handled. It should be recognized that the disturbance of handling can result in changes in their appearance. When birds are caught or removed from cages, they should be restrained quickly and with as little disturbance to them and their pen mates as possible.

        Manipulation of birds generally causes stimulation of most of the systems of the body. As a result, physiologic performance is altered and signs of disease may be masked or lost completely. This phenomenon is particularly true in cases of respiratory difficulty. Gasping birds commonly discontinue breathing through the mouth during the period they are being handled.

        With excitement, depressed birds can brighten and nervous disorders, such a drowsiness and depression, may no longer be detectable.

        It is also possible for clinical signs to be accentuated. Nervous disorders such as tremor may only be evident when the bird becomes frightened by the experience of being caught. Chickens held in a strange environment can experience an increase in intestinal motility with the production of wetter droppings.


        Poultrymen can increase their skill in detection of abnormality in poultry by attention to the behavior patterns of normal healthy flocks. If each time a pen or caged area is entered, a visual check is made of the birds and the amount and type of noise they are producing is noted, the poultryman will quickly learn what is normal for such a flock.

        The adoption of a routine procedure for viewing the birds is also helpful. Many servicemen follow the practice of looking at the droppings, checking the posture and activity, then scanning the head, plumage and legs of their birds.

        In the diagnosis of poultry disease, all deviations from normal should be noted. However, it is necessary to recognize that a flock of birds is a population composed of many individuals. While all evidence of disease is important, emphasis should be placed on the determination of the cause of problem hazardous to the flock. This can be accomplished best by developing a pattern of disease signs that applies to a number of individual birds.

        Several biologic principles can act to make the diagnosis of disease on a population or flock basis difficult. In every large flock a few birds will experience disease on an individual basis. While they are sick, they do not represent the condition of the flock. Individual birds weakened or stressed by another disease generally are more susceptible than their pen mates when some agent threatens the entire flock. As a result, they are more likely to be early victims of a general problem. If the initial disease they suffer is of a type that produces obvious and easily discernible signs, the observer may overlook the more important threat.

        Several procedures can be employed to reduce the chances of error as a result of the operation of these principles. Examination of a number of birds will eliminate the unrepresentative individual bird. Checking of birds scattered throughout the building will also insure that the sample indicates the condition of the flock.

        Two techniques will help differentiate disease agents acting concurrently. Repeated observations spaced over several hours will establish differences in the development of two disease conditions. A detailed, rather than a casual, examination will also increase the changes of detection of a second agent.

        Descriptions of the appearance of birds with typical signs of disease can be used to determine if an individual bird is normal. Another technique is to examine a large number of birds in a flock. As a general rule, if the majority of the individuals demonstrate the same condition, then it may be considered normal.

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