Avian Moulting: Autumnal Featherloss in Chickens – Why and When it Happens

Moulting: The purposeful loss (or shedding) of scales/hair/feathers.

In late summer or early autumn, chickens begin to lose their feathers. This is one of the most alarming things for a novice chicken keeper. This, however, is perfectly normal. It is called Moulting (USA spelling is Molting).

When chicks hatch, they are covered in soft puffy tufts of fluff, which is shed and replaced by small feathers in the first juvenile moult. After a few more juvenile moults, and a lot of growing, the chicks finally acquire their adult plumage. This is then moulted off again in autumn, and replaced.

Chickens moult to replace their old, worn, torn and no longer waterproof feathers with brand new, shiny, waterproof plumage to combat winter’s harsh weather. So, during September, October and sometimes even August, chickens all over the country will look ragged, and partially hair-less. As said before, this can be quite scary for a novice chicken keeper, however is 100% normal!!!

It takes a lot of energy to grow new feathers, and lots and lots of protein! During the autumn, chicken will stop laying to concentrate on moulting. At this time, changing feed from layers pellets to breeders pellets may be advisable, as rather than egg laying, breeders pellets target fertility and beauty, and contain lots of protein which helps hens grow new feathers.

Feather eating during this period may occur, this is also not a problem as the hen is only recycling protein! If you are worried they will choke, rake loose feathers away, but ensure you feed foodstuffs that contain plenty of protein.

  • Moulting is a natural process, not a disease. It occurs over a 6-8 week period, and gradual feather-loss is okay, whereas baldness is NOT ok. If a hen is completely bald, it may be a different problem besides moulting that requires investigation.
  •  More protein, less stress and good hygiene = good moult, and good return to lay.
  • Chickens should act normally while moulting, if they stop eating or drinking, something is amiss!
  • When returning to lay, eggs may be smaller than normal, however, they should quickly return to normal!


Avian Immune System – The Police of The Chicken Body

Like all animals, chickens, as well as other poultry, have immune systems like mammals do. Below is an insight to the defence of the avian body!

Primary Defences

Innate Immunity

Acquired Immunity

  • Passive Immunity
  • Active Immunity
    1. Cellular Immunity
    2. Non Cellular (Humoral) Immunity

    Skin: The skin is the first, and primary defence. It forms a physical barrier which blocks harmful micro-organisms from entering. Therefore, invasion can only occur if the skin is broken.

    Mucous Membranes: As the name suggests, these are membranes, covered in mucous! They are found lining the digestive tract, respiratory tract and several other body systems. The mucous carries the micro-organisms away, and expels them, via nasal discharge, or out the other side in the faeces.

    Immune System: Finally, if the invaders have bypassed all the other defences, the immune system comes in. It consists of various organelles and cells which are primed to target anything alien. Many of these are harmless, but the ones that cause disease must be eradicated!

    The immune systems primary role is to recognise foreign bodies and neutralize or eliminate them. This is done by lysis (rupture) and agglugation (clumping together) of foreign bodies, or phagocytosis (engulfing and de-activating).

    Innate Immunity is one of natures tools. It is the natural, or inherited ability to resist infection or disease.

    • Some birds are naturally resistant to diseases like lymphoid leukosis because they lack the receptors that the lymphoid leukosis virus infects.
    • Chickens have a high body temperature, so diseases from other animals are usually not a problem, because the pathogen is killed at high temperatures.
    • Normally, the skin and digestive tract are riddled with naturally beneficial bacteria. These stop invaders from gaining a foothold
    • The respiratory tract has fine hairs, called cilia. These are washed over with mucous and any bacteria foolish enough to dare penetrate the tract will be washed away and expelled out of the nose.

    Acquired Immunity is a very effective type of immunity that the bird gains over its lifetime. White blood cells or leucocytes are found in the blood. These are the ”police” of the body, and they hunt the criminals! There are phagocytes, which phagocytose (engulf and deactivate) intruders, and lymphocytes which release antibodies (special globulin proteins) to bind to and inactivate the antigens.

    There are two main ways in which acquired immunity works…


    1. Passive Immunity – This involves immunity transferred from individual to individual, for example, from hen to chick through the egg. In mammals, a similar process takes place through colostrum (antibody rich ”first milk”).

    3. Active Immunity refers to the immunity gained from acquiring a disease then defeating it. The  chicken keeps memory cells in the blood, so if the chicken is re-infected, antibody producion will occur so fast that the disease will not have time to cause symptoms.

    Passive immunity

    The first few days after hatching, a chick’s immune sytem is not functional, so it cannot fight invasion for itself. The solution to the problem comes through the egg. The mother passes on some antibodies which, although short lived, will guidde the chick through the first few days of life. These antibodies are from the mother’s acquired immunity, either from  vaccines or infection, then defeat of a disease.

    The level of immunity that is passed into the egg is similar to her own level, but after the 3 weeks of incubation, this drops to half. Therefore , it is valuable for the flock manager to keep the mother’s immunity levels high, to promote the health of her chicks. If vaccination of the chick is to be considered, remember that doing so too early could cause a subdued immune response, due to maternal antibodies attacking the vaccine, but if left too late, the chick will be open to disease, and may have an excessively high immune response.

    Active Immunity

    As I said above, active immunity is where the body fights off a disease, and keeps memory cells in the blood, so at the firt sign of re-infection,  antibodies are produced, and the disease cannot take a hold. This defence is effective, but only for specific antigens.

    Active immunity is divded into two parts, namely non-cellular (humoral) and cellular…


    Non-Cellular (Humoral) Immunity

    Non cellular (humoral) immunity involves antibodies, and the cells that produce them. Antibodies only exist for a short time, and are specific to their antigen. For example, the antibody for Infectious coryza, affects only the pathogen for Infectious coryza, and not the Infectious Bronchitis virus.

    When a pathogen enters the body, it is engulfed by a phagocytic WBC, known as a macrophage. It is then transported to and exposed to the B-lymphocytes (also known as B-cells).

    B-cells are produced (in the chick) by yolk sacs, the liver and the bone marrow. After 15 days of incubation, through to ten weeks of age, these cellsare moved to an organ known as the Bursa of Fabricius (BF). When required, the BF ”programs” the B-cells to attack the antigen with antibodies. The programmed B-cells then progress onto the spleen, the blood, the cecal tonsils, the bone marrow, the Harderian gland (in the eye) and thymus (an organ which ”educates” T-lymphocytes (T cells)).

    Destruction of the BF in chicks of a young age, due to Marek’s disease or Gumboro disease, means that the chick can never program B-cells, so cannot respond to most invasions, or vaccinations.

    When invasion occurs, the B-Cells release antibodies to fight the intruders. Macrophages also join the fight, coming to gobble-up the antigens which the antibodies have inhibited. After a war is over, the B-cells produce ”memory cells” which ”remember” the intruder, so should the intruder attack again, they can produce large amounts of antibodies, to generate a quicker and more effective response than the initial attack.

    Antibodies do not have the capability to kill disease directly, rather, they bind to the pathogens and inhibit their receptors. This means that they cannot locate, and bind to the target receptor.They also acts as a ”flag” for the phagocytes (macrophages) to detect invaders! Finally, though, it is up to the macrophages to engulf, and destroy pathogens.

    Cellular Immunity

    The cellular component of the immune response involves all cells that react to a specific antigen, except for those involved in antibody production (B-cells etc). The main players here are the T-lymphocytes (T-cells). These begin as the same stem cells as B-cells, but are programmed in the thymus rather than the BF.

    T-cells are produced and programmed to perform various functions, some T-cells assist B-cells and macrophages, these are known as helper T-cells, some produce lymphokines, others (directly) destroy invading organisms. Others still are known as suppressors, and inhibit the effects of macrophages and B-cells.

    This response was first discovered when it was found that birds with a damaged BF can still fight many infections and diseases!


    These are chemicals in the form of soluble proteins, that assist in activating other components of the immune response. Almost 100 different types have been identified!

    They work by:

    • Binding to WBC and increasing their ability to fight off invasion
    • Breaking down damaged, and invading cells
    • Increasing lymphocyte production
    • Performing many other related functions.



    Avian Endocrine Systems – Hormones in Poultry

    The Endocrine system consists of various glands and nodes which secrete hormones. Hormones are chemical messengers which travel in the blood to activate target cells. These target cells have special receptors, into which only certain hormones can fit. For example, testosterone act on the male gonads, but not the adrenal glands.

    Hormones tell the body what to do. The endocrine system is closely linked to the nervous system, because both deal with communications and co-ordination, but there are a few distinct differences.

    Hormones Act slowly, and for a long period of time. They cause gradual changes.

    Nerve Impulses Act very quickly, and only last for an extremely short period of time. The changes they cause are instant.

    Below are some of the main avian endocrine glands:

    Pituitary: The pituitary Gland is sometimes called the master gland. It sits in the brain base, and releases various hormones which trigger other endocrine glands to release hormones. It has two parts, the anterior and posterior lobe. It releases:

    • Natural Growth Hormone
    • Thyroid Stimulating Hormone
    • Adrenocorticotrophic Hormone (ACTH) – Stimulates the adrenal cortex
    • Sex hormones (LuteinisingHormone (LH) and Follicle Stimulating Hormone (FSH)) – To stimulate the sex glands
    • Melanin Stimulating Hormone – Unknown function (in birds)

    The posterior pituitary also produces arginine vasotocin and stores oxytocin both of which play a role in egg yolk release.


    The hypothalamus is located centrally in the brain, at the base. It produces oxytocin as mentioned above, and plays a role in controlling the anterior pituitary gland.

    Pineal Body: This is a small gland in the centre of the brain. It produces melatnin through the ue of tryptophan (a type of amino acid). Melatonin affects electrical goings-on in the brain, and behaviour, as well as sleep.The Pineal body has been described as a ‘biological clock’ and part of it function is to alert the hypothalamus as to when  to release certain hormones. An example of this is laying. In the wild, birds only lay in spring, because the pineal body ‘tells’ the hypothalamus that spring has come, and the hypothalamus begins producing LH and FSH.

    Adrenal Glands: These are a pair of small glands, some 9mm long, located in front of the kidneys. They have two regions, the adrenal cortex and the adrenal medulla. The cortex produces 3 hormones…

    • 8-hydroxycorticosterone – A hormone with an unknown function
    • Corticosterone – Stress reaction, protein breakdown, fat and carbohydrate metabolism
    • Aldosterone – Regulates sodium retention

    The medulla produces two compounds:

    Epinephrine – This plays a role in controlling blood pressure

    Norepinephrine – Fat metabolism

    Thyroid Glands

    These two glands are found at the base of the neck, each one lying at a different side.  They produce:

    • Triiodothyronine – Involved in feather (and beak and skin) development. Scientists think it may be involved in the moulting process
    • Thyroxine Regulates carbohydrate metabolism, heat production and promotes high blood sugar and growth

    Parathyroid Glands: are two assisting bodies located behind the thyroid glands. They produce Parathormone which regulates and controls the calcium level in the blood.

    Ultimobranchial bodies: These are located behind the parathyroid glands. They produce calcitonin and lower the blood calcium, thus calcitonin and Parathormone must be in balance.

    Islets of Langerhans: This group of specialized cells is located in the  pancreas. It produces two hormones:

    • Glucagon – Raises blood sugar, and affects fatty acids
    • Insuli – Lowers blood sugar


    Gonads or reproductive organs produces these hormones:

    • Testosterone
    • Progesterone
    • Oestrogen

    All of the hormones are needed in both genders, but the amounts vary. Hens need a lot more of the latter two, while cockerels produce much more of the former. When a cockerel is casrated, he becomes a capon and stops producing testosterone. Overtime, he takes on the behaviour, and to some degree, the appearance of a hen!



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    The function and science of the avian ear

    Do Chickens have ears? Yes! And in this article I will explain how they work.

    Even though chickens ears are seen only as small,  fleshy red or white earlobes, or auriculars (also known as ear coverts), the inner ear channels and amplifies sound, and plays a significant role a one of the senses.

    Near the auriculars and below and behind the eye, the ear is located. The auriculars channel sound waves into the ear opening,  and towards the eardrum, a thin membrane that vibrates in accordance with the sound waves. The waves are passed down the columella, one of the smallest bones in the avian body, and transmitted to another membrane called the oval window via the cochlea in the middle ear. The cochlea is filled with fluid, and tiny hairs called cilia are attached to its walls. They move with the sound vibrations, as blades of grass do in the wind. Vibrations are translated into electrical impules, and sent to the brain via the auditory nerve.

    When human cilia are damaged, they never re-grow, and so throughout life, hearing slowly decreases. The same happens in birds, right? WRONG!!! Birds can regenerate their cilia!!!

    Avians also have semicircular canals, the saccule and utricle, which regulate balance, just as they do in humans.

    I hope this was interesting, feel free to browse my website!


    Chickens respiratory system- science of breathing and lungs

    Because of the energy required for flying,birds have a very high demand for oxygen. Even though chickens don’t fly much, they still maintain these characteristics.

    han being a single ‘bag’ for air, they have air sacs spread around their organs, and in their bones which help keep the pressure of air in the lungs constant.

    When a bird inhales, half the air passes through bronchi to the posterior (back) air sacs, and the other half goes to the anterior (front) sacs and the lungs. That in the posterior sacs is emptied into the lungs, rather than alveoli, gas exchange takes place between the blood capillaries and the air ‘capillaries’ known as para bronchi. Compared to mammalian gas exchange, that that takes place in birds is much more efficient because the partial pressure is the same as that of the environment.

    Their lungs are quite different to mammal lungs, because, rather t


    They have no diaphragm, and therefore air flows into the lungs and is pushed out by muscular contraction.

    Located at the bottom of the trachea (windpipe) is the syrinx, the birds voice box, and as they exhale they can crow, cluck etc…

    Hope you liked this post, please check ot my other posts!



    Chicken Housing

    Chickens like to live a life of freedom and range where they choose, but in the modern day people interefere with this, and put them in cages to lay. People now also put them into there garden for a fresh supply of eggs, but for them to remain healthy and happy they have imporant requirements including good food, a foraging area, nutrient rich greens, space and good housing.

    Runs and paddocks

    Chickens like to range wherever they choose, but mostly this is not an option because people don’t like to have their flower beds in disarray, so an enclosure in the garden will do. They prefer to have a place with trees because they dont like to stand in a place where they are vulnerable to the hot sun. Our paddocks have apple trees so they shade the birds, and also give us a summer treat!
    Fencing should be strong post and rail with chicken mesh, which should be checked regularly for holes.
    Runs should contain a sand bath, which the chickens can use at will. It should contain sand, diatomous earth or both.
    The term Free range is different to free to range, the latter refers to chickens which are not cooped up while the former is where each hen has a minimum of 4 metres square to roam.
    The standard is 4sq ft in the coop and 10sq ft in the run in mainstream production.

    Housing requirements
    There must be at least 10in perch space for each hen and there must be at least 1 nest box per 5/6 hens. There must be at least 1 drinker per ten hens and, by DEFRAs regulations, 15cm of feeder per bird.
    There must be sufficient ventilation, birds must be warm enough, but must also have fresh air available to avoid respiratory problems.
    Contrary to what some people think, chickens only lay in their nestboxes, they dont sleep in them. Therefore several birds can share a nestbox, the box must be in a quiet, dark and fairly secluded corner.
    Naturally, the place where droppings are at greatest density is in the chicken coop, where they poop in the same place every night. As a result of this, coop cleaning needs to be done at least once a week. A few small bantams in a fairly large coop need to be cleaned out once a week, while larger birds need cleaning out every two or three days.