Stress- The Silent Killer

How do we understand the word "Stress"?

The Oxford dictionary defines stress as ‘ Pressure, Burden or Compulsion when much energy is required’. All living beings have a limited amount of stored up resources at all times. These resources help them to adapt or adjust themselves to unstable conditions which at times may pose as a challenge or even as a threat. In chicken, for example, extremes of weather, Vaccination , Beak trimming, insufficient housing space and many such disturbing conditions are known to result in a greater demand for these resources. As long as these challenges are minor and passing or are within tolerable limits, the animal or bird manages to make use of it’s reserves, adjust itself to the difficult situation and come out of it with little or no damage. It is only when these challenges come in more intense forms or in greater numbers at any given time, that serious chemical and physical changes take place within the bird with far reaching consequences. This could result in Immune suppression, poor weight gain, high F.C.R and depression in egg production - in short, reduction in the general well- being as well as performance. This happens as a result of the bird’s response in trying to cope with the unfavorable factors which pose a threat to it’s very existence. Actually, the factors which interfere with the well- being of the bird are called Stressors or Stress Factors and the result of the response or the effort that costs the chicken while trying to cope with the stressor is what constitutes Stress. Interestingly, during a training session, I asked the participants to express in their own words what the term Stress meant to each one of them. Take a look at some of the notions that came to their minds: Tension, Anxiety, Worry, Fear, Uncertainty, Problem, Threat, Discomfort, Pressure, Strain, Torture, Challenge, Difficulty, Distress, Hardship, Burden, Effort, Struggle...

We often wrongly reduce chicken to creatures of the lower order thinking that they have a very low threshold for pain and feelings. It is not so, as chicken, like other animals have reasonably well developed physical senses. Unfortunately, chicken, unlike human beings do not have the faculty to ‘reason out’ and imagine a future where things could change for the better. They live only for the present and experience the immediate. For this reason, they are unable to ‘reconcile to’ or ‘accept’ any negative experience, even if it happens to be a life-saving procedure like vaccination or beak trimming as something that will do them good. They remain victims of the situation and the only recourse they have in order to survive and cope with such traumatic situations is with the aid of those physical and chemical processes about which I mentioned earlier. In short, this is done with the release of Corticosterone, a steroid from the adrenal gland whenever the chicken’s system, in an effort to survive, struggles to prepares itself to face any challenge.

Different types of Stresses

For practical purposes, We could make a distinction between what we know as Unavoidable and Avoidable Stresses - those that form a necessary part of poultry operations such as Vaccination, Beak trimming, handling for the purpose of weighing or moving, high production or rapid rates of growth etc. and those which we unnecessarily impose on the birds either through neglect or due to wrong management practices such as overcrowding the birds, making abrupt or sudden changes, providing faulty ventilation, exposing them to harsh environmental conditions like extreme temperatures and so on. Good management sense should dictate that we altogether prevent any kind of avoidable stress and at the same time alleviate the unavoidable ones.

What actually does Stress do to chicken?

Technically speaking, the hormone Corticosterone, is released by the adrenal glands when the bird’s body prepares for the ‘ flight or fight ‘ syndrome. This actually helps the bird deal with stress, but at the same time takes a heavy toll. I would like to compare stress and it’s mechanism to our familiar ATM card which provides us with ready money but not without depleting our cash reserves! Whenever a bird is under stress there is a rapid release of glucose into the blood resulting in the depletion of glycogen which is a form of sugar that is stored up as a reserve in the liver and muscles. Respiratory rate gets altered. This hormone also causes chemical changes like alteration of the pH levels in the intestines which in turn upsets the balance of micro-flora in the gut. Results are that these changes provide suitable environment for certain types of bacteria and fungi. Gastrointestinal diseases can follow. Further, several studies have shown that this stress hormone can encourage the formation of as well as the increase of free radicals inside the body. Free Radicals are substances which once produced in the system can be extremely destructive. They react with oxygen in the body and reduce it’s supply. In addition to this, they constantly turn hostile to several normal processes within the body. Stress causes damages even to the growing embryo as much as it can affect a grown up bird. In practical terms, this hormone can upset several vital systems in the chicken and gnaw into productivity. 

1. The most important requisite in the Farm manager when it comes to stress is to be aware whenever birds are in trouble or are likely to experience it. This includes planning for the occasions when birds have to be handled or subjected to difficult times, although they may happen to be necessary or natural. Let whatever has to be done, be done always keeping the bird’s comfort and welfare foremost in mind.

2. A good rule of thumb is that if you have failed to prevent or avoid stress in your birds, as a good manager quickly learn to recognize the signs of stress in your flock. The indications are several -like abnormal feathering, constant preening of feathers even in the absence of external parasites, increased aggression like feather pecking or cannibalism and even aimless and restless pacing of birds that are housed on the floor. Delay in laying eggs is also an indication since birds under stress are believed to hold their eggs longer in the shell gland beyond the normal time of laying. It is also suggested that in breeds laying colored eggs, birds which are under stress begin to lay eggs with pale colored shells. The hatchability of these eggs is also lower when compared to normal colored eggs. Recently I learnt that researchers are trying to develop a test to assess or measure the welfare status/stress in chicken by using eggs and possibly, excreta of birds. These scientists have adopted this non-invasive method because according to them “the very act of taking a blood sample from a bird can dramatically affect corticosterone levels in less than a minute.”

3. Today, given the abundant availability of therapeutic formulations in the market, the manager should learn to judiciously pick just the right ones that will do his flock good. I find that many managers needto be educated in this area because the use of vitamin, mineral and herbal formulations on farms to fight stress is very often misunderstood or indiscriminate and in fact stressful for the birds and therefore counter–productive. 

While the priority of poultry farming is the business consideration, I believe that we have the obligation of balancing it with humane methods of achieving it. Animal welfare in some countries is controlled by legislation which protects animals and birds from being subjected to unnecessary pain or distress. Even where we are not bound by law, without sounding sentimental, we owe our birds the quality of handling and care which they deserve for serving our business ends. Besides, everyone knows that the performance of chicken, like all living beings, is directly proportionate to a reasonable level of their well -being and comfort. As long as we stay ignorant or insensitive to any form of hardship that birds go through, Stress will continue to remain a Silent Killer.