Chicken Stress - What it is, what causes it - answers

Discussion in 'Managing Your Flock' started by Bantimna, Dec 20, 2010.

  1. Bantimna

    Bantimna Chillin' With My Peeps

    Sep 29, 2009
    South Africa
    I recently cam across a post about Chicken/Poultry Stress I decided I'd go and look it up and do some research 'bout it.
    I apologize if anything in the following post is incorrect, please let me know.

    Stress is a big factor in determining the overall health of our birds. Stress comes in many forms and seems to affect the best of our show birds the most. There's something inherent about the genetic makeup it takes to produce the finest colors and the best type and a bird's reaction to stress. Everyone has heard of the relationship between the 'mutt' dog and good health. The same seems true with fancy fowl. The finer the breed, the more susceptible they are to stress and disease.

    They don't call them 'chicken' for nothing. By nature, most chickens (and waterfowl), are cowards. They're afraid of their own shadow (not every single chicken, and definitely no my neighbours!). Poultry are prey and their genetic code predisposes them to the flight instinct, even when they're hand-reared and tame. Fear creates stress and there's a sound medical reason why stress allows disease to take hold in an otherwise healthy bird. Without giving you a poultry veterinary science lesson, let's just say that stress causes changes to occur in the gut that lowers the pH. When the pH is low, 'Gram negative' bacteria become comfortable in the environment and begin to take hold and replicate. The rest you can imagine...

    But let's talk about the many things that stress out our birds. Some of these may be a surprise to you. My first example is severe cold or heat - or a dramatic change from one to the other. Only healthy birds are capable of making it through the night when it's sub-zero. And only healthy birds are capable of enduring severe heat if there's no water, breeze, or shade for them to find relief in. Poultry are more susceptible to this than people realize. Have you ever seen the flurry of activity that takes place right before nightfall amongst the wild birds? They're filling up with food and water to make it through the night. You can almost tell when a storm is coming because they'll sense the barometric change and feed heavily to weather the storm. Your own chickens and waterfowl will have a last meal and drink at dusk - before they can't see anymore to roost and settle in for the night. If you can't feed and water twice in a particular day and you have a choice, choose to feed and water late rather than early for the above reasons. The late feed is most important during cold weather.

    Another concern of cold weather is frostbite. Single comb varieties with long wattles suffer the most (Such as Leghorns, Dorkings etc..). Some believe that massaging Vaseline into the comb will help prevent frostbite. Keeping drafts out of the coop to keep wind chill effect down is probably more effective. A sign of frostbite is having the comb or wattles turn white. Eventually they turn black and scab over. In severe cases, the bird will lose the part that turns black.

    Breeding and laying are stressful for many reasons. It's especially stressful if it's the first season of maturity for either gender. (Most losses due to diseases such as Mareks occur right before or right after sexual maturity.) I've heard old wives tales about young roosters 'going crazy' if they're not allowed to breed. I don't think there's medical poultry science to support that - but you get the picture. 'First egg' for a female can be difficult - both in the hormone changes that occur and in the 'effort' it takes.

    Physiology of stress in poultry

    Central Avian Research Institute,
    Izatnagar(UP)-243 122

    Homeostasis mechanisms maintaining the constant internal environment in the body thereby keeps the normal physiological function of the animal / birds. A deviation from normal condition is called the stress. Generally the term “Stress” is used to describe the detrimental effects of variety of factors on the health and performance of poultry. Birds have limited body resources for growth, reproduction, response to environmental changes and defense mechanism (Rosales, 1994). Under the stress conditions, there is redistribution of body resources including energy and protein at the cost of decreased growth, reproduction and health (Beck, 1991; Brake, 1987; Gross and Siegel, 1987). Under the long term stress condition or repeated stress, birds became fatigued and weak. These conditions lead to birds starvation and infectious disease (Dohms, 1990; Freeman, 1987). Domestic birds are subjected to frequent stress factors, and therefore it is important to have an effective management program to minimize their effects on the performance and health of the birds, identifying and managing factors that causes stress in birds is a critical part of a successful poultry production. Under this paper physiological mechanisms of stress, common causes of stress, types of stress, effect of stress in poultry (physiological indicator of stress) and future course of stress managemental practices in birds are discussed.

    Physiological mechanism of stress regulation

    Exposure of birds to stress is an inevitable event in poultry husbandry, when the threshold level of stress is crossed it results in distress to birds. Then the birds show stress syndromes, which are classified into three stages.

    Stage of alarm reaction (Neurogenic system).

    •Stage of resistance or adaptation (Endocrine system).
    •Stage of exhaustion.
    1. Neurogenic (sympatho- adrenal) system (Short-term regulation of stress): This system consists of sympathetic (post ganglionic) nervous system and adrenal medullary tissue. It controls the rapid response to the animal i.e. fight or flight or alarm (emergency) reaction (Cannon, 1929). This reaction lasts only a short time. It is characterized by increased rates secretion of the catecholamine from the adrenal medulla. These catecholamines prepare the bird for "Fight or Flight" reaction and commanding a rapid release of glucose in blood, depletion of liver glycogen, increased peripheral vasomotor activity, altered ventilation rate and increased neural sensitivity (Selye, 1950; Siegel. 1980). Catecholamines also stimulate the activity of hepatic adenyl cyclase, the enzyme required for the production of cAMP (Robinson and Sutherland, 1971). cAMP regulates the number of energy reaction (physiological processes) and directly increases the formation of antibody (Braun et al. 1971).

    2. Endrocrine system (Long-term regulation of stress) : Involvement of endocrine system in stress regulation is called the 'stage of resistance'. This system is comprised of hypothalamus-pituitary adrenal axis (HPA). It is characterized by adrenal cortical hypertrophy and increased synthesis and release of adrenal glucocorticoids, known as corticosterone in bird (Siegel, 1971, 1980). Activation of the HPA is a longer-term adjustment by the animal to the surrounding changes. Selye (1936) called it General Adaptation Syndrome (GAS).

    The endocrine mechanism of stress regulation is started with the stimulation of hypothalamus and release of ACTH from anterior pituitary, which causes the increase of adrenal cortical steroid secretions. Continuous stimulation to adrenal cortex leads to chronically high levels of corticosteroid hormone. This hormone is responsible for the formation of glucose from body's reserve of carbohydrates, lipid and proteins. Corticosteroids contribute to many of the disease associated with long-term stress, such as, cardiovascular and gastronistestinal disease, hypercholesteraemla, metabolic rearrangements and antibody suppression. (Siegel, 1985).

    Other hormones:

    i) Glucagon: The α cells of the pancreas are the source of glucagon, are stimulated in alarm response in both mammals and birds (Freeman. 1980).

    ii) Thyroid hormone: Hormone produced by thyroid glands are also involved in stress regulation (Klandorj et al. 1978).

    3. Stage of exhaustion:

    Finally, if the bird does not recover from the stressor and the availability of body reserves and hormones from the adrenal gland are inadequate, a third or exhaustion phase leads to fatigue of the homeostatic mechanisms and death (Brake, 1985; Freeman,1987; Maxwell,1993).

    Types of stress:

    It was suggested to keep growing poultry in houses containing different climatized sections for resting and for activity (locomotion, water, food intake) because birds are able to choose their optimum temperature area in relation to their needs (Tzschentke and Nichelmann, 2003, Tzschentke, 2004). In addition, it must be an acknowledged that even in state of the art facilities, there are common sources of stress, which can be grouped under, one or more of the following categories (Freeman, 1987).

    Climatic stress (extreme heat and cold, high humidity) (Chancellor and Glick, 1960; Regnier and Kelley, 1981).

    •Environmental stress (bright light, wet litter, poor ventilation) (Chancellor and Glick ;1960 Regnier and Kelley, 1981).
    •Nutritional stress (shortages of nutrients, feed intake problems) (Ben-Nathan et al. 1981; Gingerich, 1992; Glick et al. 1981).
    •Physiological stress (rapid growth, process of maturing sexually) (Freeman, 1987; Mauldin, 1992).
    •Physical stress (catching, immobilization, injections, transport (Jones et al.1988; Gregory et al.1992).
    •Social stress (overcrowding, poor body weight uniformity) (Gross and Siegel, 1981; Craig, 1992; Guhl, 1958).
    •Psychological stress (fear, harsh care takers) (Beuving et al.1981).
    •Pathological stress- Exposure to infectious agents is a common source of stress, however challenges may not result in overt disease. When sub-clinical infections due to poor bio-security and sanitation persist, excessive activation of the immune system will result in a condition known as immunological stress. This condition results in a series of changes in nutrient metabolism induced by mediators of the immune response.
    In addition to the categories of stress mentioned above, all the possible types of stressors can be broadly classified under two categories (a) avoidable stressors (b) unavoidable stressors

    Avoidable stressors Un-avoidable stressors

    Overcrowding Extreme weather
    Poor ventilation Handling
    Wet litter Vaccination
    Toxins in feed Transportation
    Starvation Rapid growth
    High ammonia level Debeaking
    Dehydration Lighting
    Poor management Medication

    Effective stress management involves complete elimination of avoidable stressors and minimizing the load of unavoidable stressors on the birds.

    High ambient temperature in the tropics, like that of ours in India accompanied by high relative humidity is one of the most important stressor. Birds are more susceptible to high environmental temperature than low environmental temperature due to absence of sweat glands in the feathered body, fatty nature and high body temperature (40.1 0 C to 41.6 0C). The degree of susceptibility to tropical heat stress is higher in broilers than layers. Among broilers males are more susceptible to heat stress than females (Marin, Good layers housed in cages are more susceptible than poor layers reared on deep litter.

    Physiological indicator of stress in poultry

    Several workers have reviewed the effect of stressors in fowl (Brown 1967, Freeman, 1971, 1976). They found the following indicators of stress in birds:

    Atrophy of the thymus and atrophy of the bursa of fabrics in young birds, enlargements of the anterior pituitary and the adrenal glands. Depletion of the adrenal cholesterol. A rise level of plasma corticosterone, insulin or glucagon.

    •Increased reliance on glucose as an energy source.
    •Hypoglycemia (increased glucose utilization).
    •Decreased growth and increased muscle degradation.
    •Release of acute-phase cytokines (monokynes and lymphokynes)
    •Impaired growth of cartilage and bone.
    •Synthesis of specific heat shock proteins.
    •Decreased voluntary feed intake (anorexia)
    •Increased body temperature

    Changes in the level of plasma metabolites (e.g. glucose, tryglyceride, non-estrified fatty acids and lactate). Epinephrine content in yolk of donor hens also serves as a very good tool to reflect stress load in layer stock. Changes in the numbers of circulating leucocytes profiles (heterophil: lymphocyte ratios and basophil and eosinophil numbers).

    •Excess fat deposition in the abdomen (abdominal fat pad).
    •Ascites (water belly) in high producing broilers.
    Common causes of stress in birds

    Some of the most common causes of stress in poultry as categorized by Rosales (1984) are summarized as follows :

    •Poor brooding conditions (low temperatures, cold water)
    •Contaminated premises (built-up litter, early exposure to various disease agents)
    •High stocking density (limited feeder and dringker space)
    •Temperature exteremes (cold and heat)
    •Handling, weighing, vaccination, grading and transport (pain, physical damage)
    •Beak trimming (handing pain)
    •Lack of body weight uniformity (magnified differences in the packing order)
    •Rapid growth (Strict nutrient demand)
    •Quantitative feed and water restrictions (frustration, hunger)
    •Postvaccinal reactions (reduced feed intake, fever)
    •Feed quality problems (variation in nutrient content)
    •Long or uneven feed distribution (split feeding)
    •Sex separate feeding (pressure to restrict body weight gains)
    •Harsh caretakers (poor husbandry)
    •Inadequate ventilation (deterioration of the air quality)
    •Clinical or subclinical diseases (reduced feed intake, fever, pain)
    •Poor litter conditions (wet and cold)
    •Sexual maturity and onset of egg production (drastic stimulation with feed and light)

    Last edited by a moderator: Dec 20, 2010
  2. WoodlandWoman

    WoodlandWoman Overrun With Chickens

    May 8, 2007
    That's a good post! When people think about stress, they usually think only in terms of emotional stress. People trying to breed wild caught species usually think in terms of all different types of stress, including nutritional and environmental set-ups. Really, anything that is not right for that species, is a stressor. I'm really glad you posted this.
  3. CMV

    CMV Flock Mistress

    Apr 15, 2009
    Thanks for a very informative post. I am bookmarking this for future reference.
  4. ChickenWisperer

    ChickenWisperer Chillin' With My Peeps

    Jun 30, 2008
    Very nice. Thanks for sharing!

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