Episode 33: Chicken Biology Pt 2 (Digestive, male reproductive, Nervous, Circulatory Systems)
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Homestead Updates
Happy Turkey Day! I don’t support the glorification of colonial history, which inevitably involves the genocide of native peoples (and I’m not throwing shade here; I’m British, that’s basically most of our history) but I do appreciate the idea of a holiday that encourages reflection upon what we’re grateful for. Also an excuse to eat delicious food! Like pumpkin pie, which I refused to eat for too many wasted years due to its orange colouring.
I know people are struggling due to the pandemic and 2020 generally being a tough year. It’s okay if you’re not doing okay and feel at the end of your rope or even broken. Holidays can make feelings of fear, anxiety, and hopelessness even worse. Please reach out for help if you need it. Call a friend or family member; set up an appointment with a therapist; ask for medication if you feel it will help. For those with insurance that doesn’t cover mental health care, please remember that your regular doctor can diagnose medication for you, including antidepressants.
If you’d like to pursue therapy but don’t have the medical coverage, there are a number of companies that offer it affordably now, such as Talkspace
If you’re in crisis, the National Suicide Prevention Lifeline (US) is 1-800-273-8255. Canadians can call 1-833-456-4566. UK folks: 01708 765200. Australians: call 13 11 14
I’ve been under the weather due to a sinus infection. Had to get COVID tested (negative!), and didn’t help myself by digging up 10ft of water pipe while sick.
Meatbutt’s bumblefoot reached a point where I could take the bandage off and let the skin harden. This is good because the rooster was very upset about me manhandling her and has taken to waiting until I turn my back so he can run and chest-bump my legs. It’s adorable and not at all intimidating!
Still no name for the rooster just yet but I’m considering PepperJack, as well as Cheddar for the hen. Because what’s nearer to my heart than cheese?! I love him so much, it’s ridiculous. He’s grown some already and is the size of a small dog. He will now snatch food out of my hand, which is big progress. If anything happens to him, I am going to be a wreck. He’s wonderful!
I've raked SO MANY LEAVES in the past two weeks that I'd probably be asked to join the American team if it were an Olympic sport
A 24 hour power outage made me keenly aware that we have become complacent and are no longer properly prepared for issues. We are well water so lost running water and I had no water jugs on stand by for flushing the toilets or just to drink. I was waiting on the results of my COVID test when this all happened so couldn’t go anywhere, which meant my poor husband had to handle everything while also trying to figure out how to get work done.
Need new tubs for the reptiles so we can throw them into them during emergencies faster. As it stands, it took us 1 ½ hours at 3am because we let this slide and had to dig around for supplies
Going to bite the bullet and invest in a whole house generator. Price range is $3-10K depending on your needs, and we’ll likely be in the 7K range all things accounted for but it will be worth it long term. Our neighbour loves hers and says it’s worth every penny. Home ownership is very much about building up your savings and then watching it go down when something pops up!
Hive News
Not much to say as the weather has been too cold but, on a couple of mild days, all the hives were active so they’re hanging in so far.
Considering buying packages for next year. I was going to get another Saskatraz package but I’m worried they’re responsible for a lot of the robbing that went on this year so I’m currently learning towards Carniolan.
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Sources:
‘The Chicken Health Handbook’, Gail Damerow (primary)
‘Raising Chickens for Dummies’, Kimberley Willis, Robert T. Ludlow
Digestive System
Digestion starts in the mouth/beak
Chickens have no teeth and so cannot bite/tear food or chew it
If food is too large to be swallowed whole, chickens will attempt to tear it into smaller pieces or engage in ‘tidbitting’, which is when a bird repeatedly picks up and drops food in an attempt to break it into pieces
Like us, chickens produce saliva
Saliva: contains enzymes that start breaking down food while still in the beak/mouth, and also functions to soften food to ease swallowing
The tongue then pushes the food to the back of the throat to be swallowed
Food travels down the esophagus (tube leading to the crop) and is temporarily stored in the crop where it continues to soften
Crop allows a large amount of food to be stored, which enables a chicken to maximize a food source
As prey animals, being able to eat a large portion of food and then retreating somewhere safe to rest and digest is a key component of survival
When full, the crop is about the size of a golf ball and can be seen at the base of the neck, above the breast
The crop releases food a little at a time
How long it takes the crop to empty depends on the hardness and consistency of the food consumed; a crop full of grain can take as long as 24 hours to clear, whereas commercial food will move through much faster
From the crop, food moves to the proventriculus (‘true stomach’) where acid and enzymes start the next stage of digestion
From here, the food then moves to the gizzard (‘mechanical stomach), sometimes called the ‘chicken’s teeth’ because it grinds the food into particles
If food is not being digested well in the gizzard, it is sent back to the proventriculus
The gizzard has very strong muscles, a tough lining, and usually small stones/grit to help grind up grains and fibrous foods (I thought these stones were stored in the crop so this is news to me!)
Chickens need to continually eat fresh grit as it is eventually worn down and digested (providing nutrients)
Chickens fed only commercial pellets or crumble don’t need grit as it’s soft enough to digest without but those that eat a varied diet, including grains, should have access to it
Mineral grit: calcium carbonate, aka calcium grit; oyster shells commonly sold as it acts as a calcium source and grinds food up in the gizzard. Available in different sizes, including ‘chick grit’, but extra calcium is not recommended for birds not close to laying as it can interfere with bone development and cause kidney damage. Hens that are no laying, as well as roosters, can actually overdose on calcium grit if given free access to it
Inert grit: hard form, often washed river sand or granite. Good for young birds and roosters to avoid excess calcium.
Laying hens should be offered both types of grit, and will eat both as needed
Sometimes, chickens will eat small, sharp objects like pieces of wire or glass; these foreign objects get lodged in the gizzard and the grinding motion causes it to damage the organ
Traumatic ventriculitis: commonly known as hardware disease; bird will waste away and perish without surgical intervention (but that’s no guarantee as chickens often do not do well during surgery)
Keep your chicken yard free of debris!
Crop Binding
When the crop becomes impacted with food or foreign material
Can occur if chickens eat too much after a period of little to no food
Also occurs if chicken eats bedding/nesting materials or some other non-food item
Fibrous vegetation can also cause this condition
The swollen crop prevents movement of food through the digestive tract, causing the bird to starve to death
An extremely swollen crop can even push on the windpipe until the bird suffocates
If a bird is losing weight and has a full, hard crop, it is likely impacted
To verify impaction, isolate chicken from food overnight and check crop in the morning; a normal crop will be mostly empty by morning
Sometimes, an impacted crop can be resolved by offering a few drops of vegetable oil (via needleless syringe in the mouth); gently massage the crop to get things moving
Otherwise, the crop needs to be surgically emptied by your vet
If no vet is available and the chicken is in danger of dying, ‘The Chicken Health Handbook’ outlines the following steps:
1/ Disinfect skin over the crop
2/ Use sharp blade (fresh razor or a boxcutter) to make small cut in the skin
3/ Pull skin to one side and make a small incision through the crop
4/ Gently remove the crop contents and rinse out with saline solution
5/ Isolate the bird and keep wound clean while it heals
Pendulous Crop
Feels baggy and squishy
Distended so that the muscles get stretched beyond their ability to bounce back
The more the bird eats and drinks, the more the crop bulges, eventually it hangs down and swings back and forth (hence the name)
Why this happens is unclear
Could be due to loss of muscle tone as bird ages
Irregular access to food and water might play a role; empty/overfull crop
Some birds seem to do fine with this condition but others might develop a condition called sour crop
Sour Crop
Caused by a yeast that lives in the digestive tract that grows out of control
Treating successfully at home is difficult so seeing a vet is recommended
The Intestines
Duodenum
Upper portion of the small intestine
Forms a loop
Within the loop is the pancreas
Pancreas: secretes enzymes to aid digestion, bicarbonate to neutralize acids, and hormones to regulate blood sugar
Sharing a common duct with the duodenum is the liver, located at the end of the duodenum loop
Liver: secretes green bile (aka gall) to aid in the absorption of fats
Attached to the liver is the gallbladder, where the bile is stored until needed
The duodenum primarily functions by using enzymes to break down the food for digestion, as well as regulating the rate of digestion
Jejunum
The middle portion of the small intestine
First part of the lower small intestine
Specializes in absorbing fully digested carbohydrates and proteins
Meckel’s Diverticulum
Small, blind pouch
Roughly in the shape of a comma
Protrudes from the lower small intestine along the area where the jejunum transitions into the ileum
Permanent vestige of the yolk stalk that connected the yolk sac to the developing embryo during incubation, and through which the yolk sac was absorbed after the bird hatched
Ileum
Not as long as the jejunum but functions similarly
Absorbs nutrients, primarily vitamin B12 and other substances the jejunum doesn’t absorb
Also absorbs moisture, causing digestive contents to grow progressively thicker as they pass through
The Ceca
Branch off as a pair of blind pouches (only one opening) where the small intestine joins the large intestine
These pouches gather fluids, materials dissolved in the fluid, and extremely small digestive particles to maintain a reservoir of microflora for the proper fermentation of digestive contents
Results in the production of all 8 B vitamins
Absorbs moisture and fiber
Empty their contents approximately twice a day as cecal droppings, which are softer and smellier than regular droppings
Cecal droppings might be mustard yellow, chocolate brown, or greenish brown
The Colon/Large Intestine
Last portion of the intestine
Relatively short
Absorbs moisture from digested food, which accumulates in the fecal chamber until it is passed as droppings
A healthy chicken produces normal grey-brown droppings 12-16x a day. Little poop machines!!
Enteric Diseases
Enteric = refers to the intestines
Both small and large intestine are populated by beneficial microbes (microflora) that aid digestion and enhance immunity by outcompeting invading microbes
When balance of the native microflora is upset or overrun by invading organisms, the result is enteritis, which is inflammation of the intestine
Colitis = inflammation of the colon
Enteric diseases tend to be complex; a combination of infection, viruses, worms, protozoa, and natural microflora
The mix determines the severity of the disease
Need to know the cause to treat (vet recommended)
Symptoms include diarrhea, increased thirst, dehydration, loss of appetite, weakness, weight loss and/or slow growth
Cloaca
The large intestine ends at the cloaca
Cloaca in Latin means ‘drain’
Digestive, urinary, and reproductive tract all meet at the cloaca
The cloaca is bell shaped; loosely divided into 3 chambers/compartments, partially separated by sphincter-like muscle ridges
1st chamber = fecal chamber; at the end of the colon and is the largest chamber where final moisture is absorbed. Can hold a lot of poop, as seen in broody hens who will hold their feces for long period of times to avoid leaving the nest
Middle chamber = urogenital chamber; the smallest one where urinary tract and reproductive system ends. From the urinary tract come urinary salts, which are seen as white cappings on droppings. The rooster’s reproductive system deposits semen into this chamber. The hen’s system deposits eggs.
Final chamber = discharge chamber; the shortest chamber that exits at the event. The cloacal bursa (discussed in last week’s episode; part of the immune system) opens into the upper wall of this chamber
Urinary System
Consists of kidneys; no bladder
Kidneys connected to the urogenital chamber of the cloaca via tribes called ureters
Kidneys function to balance electrolytes, filter water, and remove wastes from the blood
In humans, these wastes removed from the blood are excreted as urine
Healthy chickens don’t excrete much liquid urine; instead, they expel blood wastes in the form of semi-solid uric acid called ‘urates’ (or uric salts); white, pasty caps on droppings
Fun fact: reptiles also produce urates!
A chicken under stress, including heat stress, may pass large amounts of liquid urine
Water deprivation, excess dietary protein or calcium, and certain diseases can cause improper metabolism of urates
Droppings may contain an excess amount of urates (as seen in spirochetosis, aka fowl tick fever)
Urates may accumulate in the joints (called articular gout)
Urates can also collect as crystals that block the ureters (seen as a symptom of infectious bronchitis)
Reproductive System (Male)
-Female reproductive system was discussed in Episode 31
-Roosters have 2 testi (testes) that each store semen in an epididymis (convoluted duct)
-Two semen ducts transport semen to the cloaca’s middle chamber (urogenital chamber)
-Each semen duct ends in a papilla; a small, nipple-like bump
-These papillae serve as a rudimentary penis
-Mating occurs when the rooster presses his cloaca to the hen’s; called the cloacal kiss
-The hen squats and lifts her tail, and the rooster jumps on her back and bends his tail down
His balancing causes his claws to slide against the hen’s back in a process called treading
If a hen is over mated, she can lose her feathers on her back, resulting in becoming scratched by the rooster’s claws; a mating saddle can help with this
Fertility
Many different things can affect the fertility of a rooster, including stress, temperature extremes, nutritional deficiency, obesity, parasites (internal and external), medication, pesticide, toxin, and disease
Daylight hours also affect fertility; with lowest fertility during time of year when the daylight hours are fewer than 14; hens often stop laying at this time, and the rooster’s testes temporarily shrivel. If you want to have year round fertility, provide lighting as you would to keep your hens laying.
Chicken sperm are viable and active at body temperature, unlike in humans where sperm production occurs at 93.2F/34C, which is below normal body temperature
Young roosters of good fertility produce more than 30,000 sperm per second!!
As a rooster ages, sperm production declines
Roosters vary in age of sexual maturity with fast-growing breeds reaching maturity at around 20-25 weeks, while slower-growing birds take longer
Epididymal Stones
Roosters over the age of 2 may experience reduced fertility (or infertility) due to stones accumulating in the epididymis region
This condition is called epididymis lithiasis
These stones are similar to kidney or bladder stones in humans
Can cause the testes to atrophy
It’s unclear what causes this condition
Theories include hormone imbalance, infection, and genetics
Male chickens are the only birds known to develop this condition, and is is more common in industrial flocks (almost 100% occurrence) vs backyard flocks (50% occurrence), which supports the theory that this is a primarily genetic condition caused by breeding for rapid growth, high egg production, and efficient calcium mobilization
Quick note on broodiness!
Hen reproductive system was discussed in detail on episode 31; please revisit to learn more
What is broodiness? When a hen stops laying, refuses to leave the nest, and hisses/growls if disturbed, she has ‘gone broody’
The instinct to incubate her eggs has been triggered
Usually occurs in the Spring as days begin to lengthen
The hen’s pituitary gland releases prolactin, a hormone that causes her to stop laying. She will not continue until her clutch of eggs she is incubating hatch
You can attempt to ‘break broodiness’ by cooling her stomach by removing her from the nest and placing her in a wire-bottomed, raised cage/crate
You can even try putting ice cubes in the nest box to cool her off!
There is a genetic component to broodiness with some breeds being known to be prone to this
If you want to let your hen raise her chicks, it is recommended to remove her from the rest of the flock to prevent another hen chasing her off the eggs (resulting in them cooling and therefore inhibiting their incubation); place her in a secure area with her nest and make sure food and water is readily available
Incubation takes 21 days; keep an eye on her during this time
The Nervous System
Complex system that coordinates all other systems to control body functions
Central nervous system consists primarily of the brain and spinal cord
Peripheral nervous system is a network of nerves connecting the organs and body parts to the brain and spinal cord
Stimulation of the peripheral nervous system sends a signal to the central nervous system for interpretation
Based on the interpretation, the peripheral nervous system responds through one of the following 2 groups of nerves:
Somatic Nerves: these use skeletal muscles to control voluntary movement (running, eating, feather ruffling)
Autonomic Nerves: control involuntary body functions (breathing, heartbeat, digestion, etc)
The nervous system can be disrupted by many things including poisons, viruses, tumours, or hereditary defect
General symptoms of a nervous disorder include lack of coordination, trembling, twitching, staggering, circling, neck twisting, convulsions, paralysis.
Eyes
Part of the central nervous system
When an image is detected, a network of nerves in the retina at the back of the eyeball send a signal to the brain for interpretation
Like most birds and prey animals, chickens have eyes on the side of their head, which gives them a larger peripheral vision but smaller binocular vision
Humans eyes focus at the same time
Chickens have a right-eye system and a left-eye system; each have different but complementary abilities
The right-eye system works best for activities requiring recognition, such as identifying food on the ground
The left-eye system works best for activities involving depth perception, such as tracking a hawk flying overhead
Working together, this means that a chicken is able to view the ground and the horizon simultaneously
Chickens have better colour vision than most animals, including humans
Their retinas are designed to see well during daytime (looking for food, keeping an eye out for predators, etc) but the downside of this keen system is that their night vision is quite poor
Mercedes vs Jaguar funny commercial: https://www.youtube.com/watch?v=nLwML2PagbY&list=PLMQrDNsc92hfeDbtlo2pDoDgbahWKvpr_&index=9&t=0s
Eye Structure
The protective covering of a chicken’s eye consists of 3 eyelids: the upper and lower lids are much like our own, except that a chicken’s lower lid moves more freely than the upper (it’s the reverse in us)
-he third eyelid is called the nictitating membrane, and moves horizontally across the eye from front to rear. It is transparent.
nictare= to blink (Latin)
The nictitating membrane lies between the eye and the eyelids, and has its own lubricating duct that is similar to our tear ducts
The nictitating membrane cleans and lubricates the eye, as well as offering a small layer of additional protection
Ammonia fumes, excessive dust, and chemical fumes can all cause irritation and damage to the eye
There are also many bacterial diseases that can affect the eyes
Symptoms of disease include swelling of the eyelids, foamy discharge, sticky/smelly discharge, cloudy eyes, and blindness
How to tell if a chicken is blind
A blind eye is usually smoky or grey in colour
The pupil is irregular in shape
If only one eye is blind, the pupils will likely be different in size
To test for blindness, slowly move one finger towards the chicken’s eye; the bird will not blink or move away if vision has been lost
Do not wave your hand as the chicken might respond to the displacement of air
A chicken can do fine if blind as long as they’re kept in a fully secure, safe environment with easy access to food, as well as companionship
Blind chickens need to be watched carefully for signs of weight loss or other symptoms that indicate a more severe infection or cause of blindness
Stargazing
Aka congenital loco: nervous conditions seen in chicks that causes the neck to bend so far back that its head touches its back and the beak points to the sky
Epileptic-like muscle spasms pull the head back, usually causing the chick to fall over
Onset is immediately upon hatching; death is inevitable
Commercially, these chicks are euthanized so very little study of the condition has occurred
A few studies seem to indicate that the cause might be due to a defect of the ear structure
A similar condition is sometimes seen in chickens that are a few days old but the symptoms are sporadic and the chick will eventually recover
Ears
Part of the nervous system
Chickens have no external ear parts; just small openings on the side of the head, below and behind the eyes
Tiny, soft feathers protect the ear openings and direct sound into the earholes
A chicken’s ear is made up of 3 chambers: outer, middle, and inner
The outer and middle ears are filled with air and are separated by the eardrum
The middle ear structure is not as complicated as a humans, though it is still a well developed sound-conducting structure
The inner ear is more complex and is filled with fluid; when a chicken moves its head, sensitive hairs in the inner ear are moved by the flowing fluid, which transmits information to the brain about where the chicken’s head is located at all times
This mechanism means that the inner ear is also responsible for balance
If this signal is disrupted, the chicken will lose coordination
Problems with chicken ears are uncommon but do occasionally occur
An infection of the outer ear is typically caused by bacteria or fungi, and causes swelling, itching, fluid discharge
An infection of the middle ear is usually the result of a chronic bacterial infection, and causes swelling
Infection of the inner ear is usually the result of a virus, and symptoms include loss of coordination and twisting of the neck
Tumour growth might press upon the ear, causing symptoms similar to that of a chronic infection
Outer ear infections are the easiest to treat; keeping the ear clean and applying an antimicrobial is usually enough to resolve the issue
Inner and middle ear problems require accurately diagnosing the source of the infection (vet needed)
Tumours are diagnosable via x-ray and are sadly untreatable
A note on headshaking
Headshaking is not always a sign of an ear infection. Chickens, especially roosters, will shake their head when nervous or scared. If during this shaking, the bird keeps an eye on you/the source of fear, it’s likely not an infection. Similarly, lack of scratching at the head also indicates this is a behavioural action.
Circulatory System
Consists primarily of heart, spleen, blood, and blood vessels
Blood makes up 6% of a chicken's body weight
Blood functions to transport oxygen, hormones, and nutrients throughout the body; carrying away carbon dioxide and other waste products; forming blood clots to minimize bleeding from wounds; carrying antibodies and infection-fighting cells; and helping to regular body temperature
Chickens can have one of twelve blood types, each with their own unique set of antigens
Blood type influences chicken’s resistance to disease, egg production and vigor, and hatchability of eggs
Some breeds are more vigorous and less susceptible to disease than others
The heart is a four chambered pump that keeps the blood circulating
The spleen's function is to clean the blood of microorganisms, unhealthy blood cells, and other debris
Blood susceptible to invasion of bacteria, viruses, fungi, protozoa, and other parasites that get into the blood through mucous membranes or through skin via wounds or insect bites
Some species of parasitic worms temporarily travel through the blood on their way to the organ or tissue in which they will mature
Septicemia
When an infectious organism enters the bloodstream and becomes generalized/systemic by invading the whole body = septicemia
Sudden death with a full crop is a typical indication of acute septicemia
Other symptoms include weakness, listlessness, lack of appetite, prostration, sudden death (acute onset)
Anemia
When blood is deficient in quantity (blood loss) or quality (low red blood cell count)
Red blood cells = erythrocytes; most numerous of the blood cells and responsible for transporting oxygen throughout the body, and removing carbon dioxide and other waste gase
Hemoglobin is an iron-rich protein within red blood cells that carry oxygen and carbon dioxide; it is bright red in colour
Red blood cells rapidly become worn out and die, and are replaced by new red blood cells
When disease or other abnormalities cause these cells to die faster or fail to regenerate, this results in anemia
Anemia can be caused by dietary copper or iron deficiency, blood sucking parasites (mites and lice), aflatoxins, some infectious diseases, or internal tumour
Symptoms include pale skin and mucous membranes, loss of energy/lethargy, weight loss, and death
Anemia from iron deficiency also causes faded plumage in red-feathered birds
Viral disease infectious anemia is the only disease based anemia
Anemia is otherwise not a disease but rather a result of some other condition
It’s essential that you find the root cause of anemia in order to treat (see your vet)
Chickens usually recover with proper treatment
Red Cell is a supplement for horses that can be given to chickens who need a nutritional boost due to anemia. Add it to their drinking water at a rate of 1 teaspoon per gallon of water.
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And that's it for the series! Thanks for reading along/listening. I appreciate you!
Now, go forth and eat obscene amounts of pie.
