ANATOMY B

RUMINANTS

A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called "ruminating".

There are about 150 species of ruminants which include both domestic and wild species. Ruminating mammals include cattle, goats, sheep, giraffes, bison, moose, elk, yaks, water buffalo, deer, camels, alpacas, llamas, antelope, pronghorn, and nilgai. Taxonomically, the suborder Ruminantia includes all those species except the camels, llamas, and alpacas, which are Tylopoda. Therefore, the term 'ruminant' is not synonymous with Ruminantia. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".

The primary difference between a ruminant and non-ruminant (called monogastrics, such as humans, dogs, and pigs) is that ruminants have a four-compartment stomach. The four parts of the stomach are rumen, reticulum, omasum, and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud or bolus.

The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fiber, especially cellulose and hemi-cellulose, is primarily broken down into the three volatile fatty acids, acetic acid, propanoic acid and beta-hydroxybutyric acid, in these chambers by microbes (bacteria, archaea, protozoa, and fungi). Protein and non-structural carbohydrate (pectin, sugars, starches) are also fermented.

Even though the rumen and reticulum have different names they represent the same functional space as digesta can move back and forth between them. Together these chambers are called the reticulorumen. The degraded digesta, which is now in the lower liquid part of the reticulorumen, then passes into the next chamber, the omasum, where water and many of the inorganic mineral elements are absorbed into the blood stream.

After this the digesta is moved to the true stomach, the abomasum. The abomasum is the direct equivalent of the monogastric stomach (for example that of the human or pig), and digesta is digested here in much the same way. Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulorumen are also digested in the small intestine. Fermentation continues in the large intestine in the same way as in the reticulorumen.

Almost all the glucose produced by the breaking down of cellulose and hemi-cellulose is used by microbes in the rumen, and as such ruminants usually absorb little glucose from the small intestine. Rather, ruminants' requirement for glucose (for brain function and lactation if appropriate) is made by the liver from propionate, one of the volatile fatty acids made in the rumen.

Comparison of stomach glandular regions from several mammalian species. Yellow: esophagus; green: aglandular epithelium; purple: cardiac glands; red: gastric glands; blue: pyloric glands; dark blue: duodenum. Frequency of glands may vary more smoothly between regions than is diagrammed here. Asterisk (ruminant) represents the omasum, which is absent in Tylopoda (Tylopoda also has some cardiac glands opening onto ventral reticulum and rumen) Many other variations exist among the mammals.

Classification

Hofmann and Stewart divided ruminants into three major categories based on their feed type and feeding habits: concentrate selectors; intermediate types; and grass/roughage eaters, with the assumption that feeding habits in ruminants cause morphological differences in their digestive systems, including salivary glands, rumen size, and rumen papillae.

There are also pseudo-ruminants having three-compartment stomach instead of four like ruminants. Monogastric animals such as Guinea pigs, horses and rabbits are not ruminants as they have a simple single-chambered stomach and digest cellulose via an enlarged cecumallowing the easy digestion of fibrous materials. Such animals are called hindgut fermenters.

Wild ruminants number at least 75 million and are native to all continents except Australia and Antarctica. Nearly 90% of all species are found in Eurasia and Africa alone. Species inhabit a wide range of climates (from tropic to arctic) and habitats (from open plains to forests).

The population of domestic ruminants is greater than 3.5 billion, with cattle, sheep, and goats accounting for about 95% of the total population. Goats were domesticated in the Near East at approximately 8,000 B.C. Most other species were domesticated by 2,500 B.C., either in the Near East or southern Asia.

Ruminant Physiology

Ruminating animals have various physiological features which enable them to survive in nature. One feature of ruminants is their continuously growing teeth. During grazing, the silica content in forage causes abrasion of teeth. Abrasion of the teeth is compensated by continuous tooth growth throughout the ruminant's life, as opposed to humans or other non-ruminants whose teeth stop growing after a particular age. Ruminants do not have upper incisors, instead they have a thick dental pad to thoroughly bite food.

The avian and ruminant species have GI tract variations warranting further discussion as they influence the diet consumed and utilization efficiency.

The avian species have variations throughout their GI tract.  

Poultry do not have teeth. Poultry use their beak and claws to reduce the particle size of the feed so the feed may be swallowed and digested. The stomach of the avian species is divided into three regions. The first region is the crop. The crop functions as a temporary storage for consumed feed. The second region is the proventriculus. The proventriculus is the glandular stomach of the avian species. 

The functions are similar to the previously discussed functions of the glandular stomach. The third region is the gizzard. The gizzard is a dense pouch containing a tough, muscular lining. The interior of the gizzard contains grit or small stones. Via muscular contractions, the gizzard grinds ingested feed. Located subsequent to the small intestine, the avian species have two large ceca. Finally, the avian species have one excretory duct therefore their excrement is a combination of both feces and urine.

This diagram illustrates the general features of a ruminant GI tract.

The ruminant species possess one significant variation in their GI tract. The ruminant species have one stomach that is divided into four compartments.

Rumen Microbiology

Vertebrates lack the ability to hydrolyse beta [1-4] glycosidic bond of plant cellulose due to the lack of an enzyme celulase. Thus ruminants must completely depend upon the microbial flora, present in rumen or hindgut, so as to digest cellulose. Digestion of food in rumen is primarily carried out by the rumen microflora which contain dense populations of several species of bacteria, protozoa, sometimes yeasts andfungi. It is estimated that 1mm of rumen contains 10-50 billion bacteria, 1 million protozoa and several yeasts, fungi.

As the environment inside a rumen is anaerobic, most of these microbial species are obligate or facultative anaerobes which can decompose complex plant material such as cellulose, hemicellulose, starch, proteins. Hydrolysis of cellulose results in sugars which are further fermentated to acetate, lactate, propionate, butyrate, carbon dioxide and methane.

During grazing, ruminants produce large amount of saliva. Estimates are within 100 to 150 litres of saliva per day for an adult cow. The role of saliva is to provide ample fluid for rumen fermentation and as a buffering agent. Rumen fermentation produces large amounts of organic acids and thus maintaining the appropriate pH of rumen fluids is a critical factor in rumen fermentation.

This diagram illustrates the orientation and relative sizes of the four compartments. The first compartment is the reticulum. The feed travels from the esophagus into the reticulum. 

Tannin Toxicity In Ruminant Animals

Tannins are phenolic compounds that are commonly found in plants. These compounds play a role in protection from predation, as well as growth regulation, when they are digested by herbivores. Found in the leaf, bud, seed, root, and stem tissues, tannins are widely distributed in many different species of plants. Tannins are separated into two classes: hydrolysable tannins and condensed tannins. 

Depending on their concentration and nature either class can have adverse or beneficial effects. When ruminants digest some plants, they acquire a surplus of tannins and rumen microbes do not have the enzymatic ability for degrading condensed tannins. In fact, digestion of tannins by ruminants in large amounts can reduce the activity and the proliferation of ruminal microorganisms reducing ruminal biohydrogenation.

Tannins can also precipitate proteins and inhibit the absorption of nutrients.^[14] Very high levels of tannin intake can produce toxicity that can even cause death. Animals normally consuming tannin-rich plants can develop defensive mechanisms against tannins, such as the strategic deployment of lipids and extracellular polysaccharides that have a high affinity to binding to tannins. These mechanisms prevent tannins from causing adverse effects on rumen microbes.

THE RUMINANT DIGESTIVE SYSTEM

The fact that the ruminant can convert roughages, unsuitable for man, into useful products is normally taken for granted. What enables them to achieve this? The ruminant has three preliminary compartments in its digestive tract before the true stomach, or abomasum. These are the reticulum, rumen, and omasum. The rumen, and reticulum are not completely separated, but have different functions.

Reticulum

The reticulum is a flask-shaped compartment with a "honeycomb" appearance. It moves ingested food (ingesta) into the rumen and the omasum. The reticulum also causes the regurgitation of ingesta during rumination, and acts as a collection compartment for foreign objects.

 

Rumen

The rumen is a large fermentation chamber (in adult cattle its volume is about 125 litres) which has a very high population of micro-organisms, mainly bacteria, but also protozoa.

It is because the bacteria secrete the enzymes necessary for cellulose degradation that ruminants are able to utilize roughage. The rumen has a textured surface, lined with projections (up to 1 cm long), termed rumen papillae. The rumen, along with the omasum, absorb the by-products of bacterial fermentation. These by-products are volatile fatty acids (VFAs).

Omasum

The omasum, or "manyplies", contains numerous laminae (tissue leaves) that help grind ingesta. These folds assist in the removal of fluid from the ingesta on their way to the abomasum.

 

Abomasum

This compartment corresponds to the stomach of the non-ruminant, and is termed the true stomach. It secretes the gastric juices which aid in digestion. The pH of the abomasum is normally in the range of 2,0 to 2,5. This low pH facilitates initial protein breakdown, and kills the bacteria which have spilled over from the rumen.

Ruminants differ from monogastric animals in the following important ways:

 

• They have no upper canine teeth, or incisors, and have long, thick and rough tongues.
• They ruminate. Chewing the cud helps reduce feed particle size, and mixes saliva into the feed.
• The ruminant digestive system includes a fermentation chamber, called the rumen. The rumen contains micro-organisms which serve some important functions: they make it possible for ruminants to digest fibre (especially those in roughages) and they synthesize nutrients (such as B complex vitamins), and also essential amino acids which become available to the animal when the micro-organisms die, and are digested.

The ruminant represents a classic example of symbiotic association between mammal and micro-organism.

RUMINANT DIGESTION

Digestion of carbohydrates

Plant tissues contain about 75 per cent carbohydrates of one kind or another, and provide the primary source of energy for both the ruminal organisms, and the host animal.

In ruminants the major part of all carbohydrates, including the complex carbohydrates such as cellulose and hemi-cellulose, is digested by bacterial action in the rumen.

During microbial digestion an appreciable amount of methane gas is produced. Approximately 6 to 7% of the food energy of the ruminant is lost as methane.

The main end-products of carbohydrate digestion are volatile fatty acids. Of these, acetic acid forms the major proportion, followed in declining order by propionic, butyric, and valeric acids. The VFAs are absorbed into the bloodstream through the rumen wall, and constitute 66 to 75% of the energy derived from the feed. Carbohydrates, such as sugars and starches, that escape ruminal digestion are digested in the abomasum, and the end-products are absorbed through the small intestine.

Digestion of protein

Dietary protein, like dietary carbohydrates, is fermented by rumen microbes. The majority of true protein, and non-protein nitrogen (NPN), entering the rumen is broken down to ammonia, which bacteria require for synthesizing their own body protein. Ammonia is most efficiently incorporated into bacterial protein when the diet is rich in soluble carbohydrates, particularly starch. Ammonia, in excess of that used by the micro-organisms, is absorbed through the rumen wall into the blood, carried to the liver, and converted to urea, the greater part is excreted in the urine. Some urea is returned to the rumen via the saliva, and also directly through the rumen wall.

The undegraded true protein fraction, plus the microbial protein, passes from the rumen to the abomasum, where it is digested, and absorbed into the bloodstream through the walls of the small intestine.

DIGESTIVE DISORDERS

Since different substances are digested by different classes of bacteria, provision must be made to allow a new population of bacteria to establish itself when changes are made in the ration. Changing the composition of a ration, therefore, should be made gradually and it may take up to six weeks for the ruminal organisms to adapt to a change in diet.

A large number of digestive disorders can occur in ruminants. Only three of the more important disorders will be discussed:

BLOAT

Bloat, to which all ruminants are subject, can be of the frothy or the free gas type, and can be either acute or chronic. The term bloat is generally used to describe any condition caused by an excessive accumulation of gas in the rumen.

Frothy bloat (Pasture bloat)

Plant-induced bloat is usually of a frothy kind, the gas in the rumen being trapped in a stable foam which cannot be eructated by belching.

The daily production of gas, principally carbon dioxide, and methane, is about 800 litres in adult cattle. Frothy bloat occurs when the rate of foam formation is greater than the rate of foam breakdown, and this process is maintained for some time. The foam persists, and accumulates, causing an increase in the volume of ruminal digesta. This makes it difficult for the animal to clear digesta from the entrance of the oesophagus (the cardia). Clearance of the cardia is necessary for eructation (belching), but eructation is not stimulated, because the foam also induces a swallowing reflex. The characteristic abnormal distention of the rumen, a marked bulging of the left flank, results from the trapping of the gas in the foam.

Frothy bloat does not result from a simple mechanism, but the main factors to consider are the plant and the animal factors.

Plant factors

Some legumes (clover and lucerne, especially) have high bloat potentials, whereas other legumes very seldom cause bloat. The dangerous phase of forages for causing bloat is considered to be the young, fast-growing, leafy phase.

Animal factors

The susceptibility to bloat is believed to be inherited, and greedy feeders are more prone to bloat. The effects of saliva on bloat cannot be overlooked. The type of feed affects saliva flow. Roughage increases it and grain decreases it. Roughage also stimulates rumen motility, and belching efficiency.

Production losses due to bloat include:

• Losses due to death, and therefore a financial loss.
• Cost of protein supplements if legumes are not utilized.
• Expense of veterinary treatment, and labour.

Practical considerations to prevent bloat:

• Much can be done to prevent bloat, e.g. roughage, especially dry hay, should be fed before, or during, the grazing of lush, immature legume pasture. This will reduce the risk of bloat occurring. The dry roughage stimulates salivation, and sufficient saliva will help prevent bloat.
• Veterinary recommendations to inhibit foam formation, or gas formation, should be followed.
• Animals suffering consistently from bloat should be tested for TB, because TB can be the fundamental cause of recurrent bloat.

Treatment of bloat

An anti-foaming agent has to be introduced into the rumen to break the froth. Any suitable vegetable oil can be used for this purpose in an emergency, if the commercial pharmaceutical preparations containing recognized anti-foaming agents are not available.

Genuine turpentine, at a rate of 1 ml/kg body mass, administered by mouth, is a well-known treatment, and probably causes the froth to break.

Remember that bloat is due not so much to excessive gas production but rather to the failure to eructate.

Free gas bloat

Acute bloat, caused by free gas, results primarily when the normal gases of rumen fermentation are trapped due to oesophageal obstruction. The only way to relieve this condition is to remove the obstruction, or in the case of emergencies, to relieve the pressure by use of a trocar.

Metabolic disorders

Metabolic disorders such as urea poisoning, and acidosis, often cause bloat in cattle.

Urea Poisoning

Urea, and other NPN compounds, are very useful compounds, especially in winter licks. However, when improperly fed and formulated, urea can be deadly poisonous.

The toxicity of urea, and other NPN compounds, is caused by excessive levels of ammonia in the blood. Urea reaching the rumen is rapidly converted to ammonia. When large amounts of urea are consumed over short periods, the microbes cannot utilize the ammonia for synthesis of microbial protein as rapidly as it is produced. The quantity of ammonia (NH₃) absorbed by the ruminant is greatly influenced by both the concentration of ammonia in the rumen fluid, and the pH of the rumen fluid.

Absorption is more rapid when the rumen fluid is alkaline (pH>7). Rumen fluid is not as well buffered against an increase in pH as against a decrease. Since the chemical structure of ammonia is alkaline, increasing concentrations of ammonia elevates the pH, and increases its absorption across the rumen wall. Absorbed ammonia is converted to urea in the liver.

Symptoms of urea poisoning are:

• Animal becomes uneasy, and nervous.
• Excessive amounts of saliva are secreted.
• Defaecation, and urination, are frequent.
• Animal struggles violently, and bellows.
• Bloat often occurs.
• Tetany (painful muscular cramps caused by intense and repeated nervous stimuli), and death occur.

Important practical considerations in the use of NPN:

• Animals unadapted to urea are most susceptible to urea poisoning
• The amount of urea fed should be increased slowly over a period of at least three weeks.
• Animals showing a definite demand for salt should be allowed only limited access to a lick containing urea.
• Diets composed primarily of poor-quality roughage often do not provide enough readily-fermentable carbohydrates for efficient urea utilization.
• Fasting, or a relatively empty rumen at the time urea is fed, increases the probability of toxicity, because the microbes are not able to utilize the rapidly-formed ammonia.
• Restricted water intake reduces rumen fluid volume, and increases ammonia absorption by the animal.
• Urea toxicity is often associated with improper feed-mixing, and/or the composition of a ration or lick containing urea.
• Rations, and licks containing urea, should be fed under cover (protected from the rain).

Therefore:

• Including urea in a ration or lick for cattle should be done with the utmost care, and consideration.
• Generally, supplemental urea should not exceed more than 1% of the total ration.
• Daily intake of 0,2 g urea/kg body mass of the animal should not be exceeded.
• Special attention must be devoted to supplying readily-fermentable carbohydrates.
• Urea poisoning can be successfully treated with vinegar. Depending on the size of the animal, five litres of diluted vinegar (i.e. 1 part vinegar to 4 parts water) is normally dosed to the animal via a stomach tube. The treatment can be repeated six to 12 hours later if necessary.

Acidosis

The production of short-chain fatty acids in the rumen is directly related to the various types, and number, of bacteria and protozoa that make up the rumen microbial population. The organisms, in turn, are primarily determined by the types of feedstuffs fed to the ruminant. Some types of bacteria, and protozoa, can digest cellulose and hemi-cellulose, but not starch. Others can digest starch, but not cellulose and hemi-cellulose, and some can utilize both, with a preference for one over the other.

When the ration is changed from predominantly a roughage to a grain ration, the population shifts towards more starch-digesters. Starch-digesting bacteria produce more propionic acid relative to acetic acid, than do cellulose-digesters. Grain consists mostly of starch, which is rapidly digested. Therefore a change to a high grain-content ration will result in a rapid increase in rumen acidity, due to the rapid production of short-chain fatty acids. During this sudden change of the ration to large amounts of grain, the starch-digesting bacteria,Streptococcus ovis, increase rapidly, and 80 to 85% of the acid produced by this species is lactic acid. At the same time, the rumen pH falls considerably, to approximately 5, and lower, and there is a tremendous increase in histamine that could lead to laminitis.

Small quantities of lactic acid are normally efficiently converted to propionic acid, but when excessive quantities of lactic acid are produced they accumulate in the rumen, and eventually are absorbedvia the rumen wall into the bloodstream.

The outcome of such a high lactic acid level in the bloodstream normally results in one or more of the following conditions:

• Rumen stasis (the digestive function of the rumen comes to a standstill)
• A major shift in the population of rumen microbes.
• Dehydration.
• Dehydration.
• Liver abscesses.
• Bloat.
• Rumenitis, and damage to the rumen villae.
• Damage to the mucosal tissue of the rumen.
• Cattle go off their feed, become weak, and appear depressed.
• Increased heart and respiratory rate.
• Laminitis.

When cattle in feedlots become adapted to high grain-content rations, a new microbial balance develops in which the proportion ofStreptococcus ovis is not high, and in which other species predominate. Cellulose, and hemi-cellulose are digested more slowly than are starch, and soluble carbohydrates, resulting in a lower total concentration of acids at any one time.

THUS: One can switch rather rapidly from a grain to a roughage ration, but NOT from a roughage to a grain ration.

Important practical considerations

• Inefficient management skills on the farm or feedlot are the main cause of acidosis (for example, when the door of the feed shed is left open, or unattended.)
• Strict control over rations should be exercised, especially when switching from roughage, veld or pastures, to grain or complete rations. Changes to a grain ration should be made gradually, over a period of at least three weeks.
• Some breeds, notably the Bos indicus breeds, seem to be more susceptible to acidosis than others.
• Acidosis seems to appear more often during the summer months.
• If a severe case of acidosis is experienced, a veterinarian should be called immediately.
• Mild cases of acidosis can be treated by dosing with:
  • 300 g of magnesium oxide powder
    800 g of activated charcoal dissolved in 5 litres of water
• If no improvement is seen within 12 hours, a veterinarian must be consulted.

THE ANATOMY OF A CHICKEN

The diagram below gives a detailed look at the external anatomy of a rooster.

The anatomy of a chicken is rather similar, however Roosters are larger birds.

Chicken and Rooster Combs

There are eight distinctive types of combs on chickens and roosters:rose, strawberry, silkis, single, cushion, buttercup, pea, and V-shaped

	The Rose is a solid, broad and nearly flat comb on top. It is a low, fleshly comb that concludes in a well-developed tapering spike at the back. It may turn upward as in Hamburg breeds, be nearly horizontal as in Rose Comb Leghorn breeds, or follow the contour of the head as in Wyandotte breeds. The top surface of the main part should be slightly convex and studded with small rounded protuberances. The general shape varies in the different breeds.
	The Strawberry is a low comb that is set well-forward. The shape and surface resemble the outer part of half a strawberry with a large end nearest the beak of the chicken.
	The Silkis is an almost round, somewhat lumpy comb, inclined to be greater in width than length; covered with small corrugations on top and crossed with a narrow transverse indentation slightly to the front of the comb. Sometimes two or three small rear points are hidden by a crest, others are without points. Generally they are considered to be genetically a rose comb changed by a rose comb plus crest.
	The Single comb is a moderately thin, fleshy formation of smooth soft surface texture, firmly attached from the beak along the top of the skull with a strong base. The top portion shows five or six rather deep serrations or distinct points, the middle points being higher than the back or front, forming a semi-oval shape when viewed from the side. The comb is always upright and much larger and thicker in males than in females. It may be lopped or upright in the female. This depends on the breed. The comb is divided into three sections: the front, the middle and that extending past the rear base of the skull, the posterior or blade.
	The Cushion  is a solid low, moderately small comb; smooth on top, the front, rear and sides are nearly straight with rounded corners. It has no spikes.
	The Buttercup  consists of a single leader from base of beak to a cup-shaped crown set firmly on the centre of the skull and completely surmounted by a circle of regular points. The cavity within the circle of points is deep, the texture of the comb is fine.
	The Pea is a medium length, low comb, the top of which is marked with three low lengthwise ridges, the centre one is slightly higher that the outer ones. The outer ones are either undulated or marked with small rounded serrations. This is a breed characteristic that is found in Brahmas, Buckeyes, Cornish, Cubalayas and Sumatras.
	The V-Shaped comb is formed of two well defined horn like sections that are joined at their base, as in breeds such as Houdans, Polish, Crevecoeurs, LeFleche and Sultans.

Both the male and female have distinctive wattles, a fleshy piece of hanging skin under their beak and combs. These organs help to cool the bird by redirecting bloodflow to the skin. In males, the combs are often more prominent, though this is not the case in all varieties.

The largest chicken egg on record weighed over 12 ounces and measured 14 inches round.

The heaviest chicken is 22lbs. (10kg approx.) and belonged to Grant Sullens of West Point, California, USA. This breed of chicken is a' White Sully'. It is known to have a very mean temper as it has been reported to have killed two cats and wounded a dog.

Chickens are quite speedy little birds, they can run about 9 miles per hour.

Particularly when being chased!

The longest distance flown by any chicken is 301.5 feet.

Chickens (Gallus domesticus) are domestic birds that cannot fly. There are over 150 different breeds of chicken that come in various colours, patterns and sizes. The chicken is believed to have descended from the wild Indian and south-east Asian Red Junglefowl which is biologically classified as the same species.

With a population of more than 24 billion in 2003, there are more chickens in the world than any other bird. Chickens provide two sources of food frequently consumed by humans: their meat, also known as chicken, and eggs which they lay.

Chickens have a great usefulness to humans. Chickens can be kept as pets, for breeding, egg laying and a food product. There are many different breeds that come in a variety of colours.

	A female chicken is called a 'hen'.
	A male chicken is called a 'rooster'.
	Young chickens are called 'chicks' or 'poults'.
	A group of chickens is called a 'flock'.

Roosters can usually be differentiated from hens by their striking plumage, marked by long flowing tails and bright pointed feathers on their necks. The rooster is larger and more brightly coloured than the hen, he also has a larger comb on top of his head.

Roosters make a very loud crowing sound usually very early in the morning but they can crow anytime of the day. Their loud shrill is a territorial sign to other roosters. They can also be quite aggressive birds. Hens lay eggs that range in colour from white to pale brown and other pale colours depending on the breed.

Chicken Diet

Chickens have a varied diet. Chickens are omnivores and will feed on small seeds, herbs and leaves, grubs, insects and even small mammals like mice, if they can catch them. Domestic chickens are typically fed commercially prepared feed that includes a protein source as well as grains. Chickens often scratch at the soil to get at adult insects and larva or seed. Chickens have a well-developed gizzard (a part of the stomach that contains tiny stones) that grinds up their food.

Flightless Birds

Although chickens are flightless birds, they do have a tendency to attempt flight. Chickens do this by runing and flapping their wings. Unfortunately, they are not capable of staying air bourne. Chickens sometimes can fly for very short distances such as over fences. Chickens will sometimes attempt flight simply to explore their surroundings, however, they will especially fly in an attempt to flee when they perceive danger or pursued by a predator.

Chicken Behaviour

Chickens are gregarious birds and live together as a flock. Chickens have a communal approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing a 'pecking order', with dominant individuals having priority for access to food and nesting locations. Removing hens or roosters from a flock causes a temporary disruption to this social order until a new pecking order is established.

Chicken Reproduction

When a rooster finds food he may call the other chickens to eat it first. He does this by clucking in a high pitch as well as picking up and dropping the food. This is part of chicken courting ritual. When a hen becomes familiar coming to his 'call' the rooster may mate with the hen and fertilize her egg.

Broody Hens

Sometimes a hen will stop laying eggs to concentrate on the incubation of her eggs. This state is commonly known as 'going broody'. A broody hen will sit fast on her nest and will protest if disturbed or removed. She will rarely leave the nest to eat, drink or dust-bathe. All the time she is sitting in the nest she will regularly turn the eggs keeping them at a constant temperature and humidity.

At the end of the incubation period, which is an average of 21 days, the eggs (if fertilized) will hatch and the broody hen will take care of her young. Since individual eggs do not all hatch at exactly the same time (the chicken can only lay one egg approximately every 25 hours), the hen will usually stay on the nest for about two days after the first egg hatches. During this time, the newly-hatched chicks live off the egg yolk they absorb just before hatching. The hen can hear the chicks peeping inside the eggs, and will gently cluck to encourage them to break out of their shells. If the eggs are not fertilized and do not hatch, the hen will eventually grow tired of being broody and leave the nest.

Modern egg-laying breeds rarely go broody and those that do often stop part-way through the incubation cycle. Some breeds, such as the Cochin, Cornish and Silkie, regularly go broody and make excellent mothers.

Chicken Life Span

The life span of a chicken varies between 5 - 7 years although there have been cases of chickens living 20 years or so.

Chicken Predators

Besides humans, lots of animals eat chickens as well. The chickens predators include: skunks, owls, raccoons, hawks, snakes, opossums, bobcats and foxes.

Chickens (Gallus domesticus) are domestic birds that cannot fly. There are over 150 different breeds of chicken that come in various colours, patterns and sizes. The chicken is believed to have descended from the wild Indian and south-east Asian Red Junglefowl which is biologically classified as the same species.

A female chicken is called a 'hen'.

A male chicken is called a 'rooster'.

Young chickens are called 'chicks' or 'poults'.

A group of chickens is called a 'flock'.

Anatomy of an egg

The color of the shell varies according to the breed: white, cream-coloured, brown, blue-green, etc. It is a genetic factor which is without effect on the food value or savour of eggs. The shell primarily consists of limestone (calcium carbonate). The shell protects eggs from the shocks and evaporation; it is semipermeable (it lets pass oxygen and carbon dioxide; it prevents the microbial penetration) and includes approximately 10 000 pores.

Under the shell are the shell membranes (outer and inner), being used a protection against the undesirable elements (moulds, bacteria).

At one end of the egg, there is the air cell. Non-existent to the moment of the laying, the cooling of the egg, brings the formation of an air cell between the 2 shell membranes.

The albumen surrounds the vitellus. It is used as a shock protection. The albumen located in periphery is more fluid. The remainder is more viscous. During the development of the embryo, it will provide water and proteins.

The chalazae are used to maintain the vitellus in the center of the egg.

The vitellus is surrounded by a thin membrane. The germ is located there and is being used as starting point for the development of future chick. For a good embryonic development, it is important that the germ remains on the top of the vitellus. This is made possible by the chalazae. The remainder of the vitellus will be used as nutritive matter for the embryo.

Eggs are a biological structure intended by nature for reproduction of birds.  They protect the developing chick embryo and provide food for the first few days of the chick’s life.  The egg is also one of

the most nutritious and versatile of human foods.

Eggs of domestic chickens may be white, many shades of brown, or yellow.  One breed lays bluegreen eggs.  Sometimes very small, dark flecks are present on the eggshell, especially if it is brown.

Egg color often assumes economic importance, as there are numerous local prejudices in favor of

shell tints.  Colored eggs occur because pigment is deposited in the shell as it is formed in the uterus.

The protective covering known as the shell is composed primarily of calcium carbonate, with 6,000

to 8,000 microscopic pores permitting transfer of volatile compounds.  The air cell is located in the

large end of the egg, and is formed when the cooling egg contracts and pulls the inner and outer shell

membranes apart.  The chordlike chalazae holds the yolk in position in the center of the egg.  As

shown, a membrane surrounds the yolk, known as the vitelline membrane.  The germinal disc, a

normal part of every egg, is located on the surface of the yolk.  Embryo formation begins here only

in fertilized eggs.

Anomalies

Eggs with a soft shell

A soft egg shell is the symptom of a lack of calcium.

Just give crushed oyster shells.

Dark shells which become pale

This can be due to stress, disease or food deficiency. Nevertheless, the main reason is to be sought is a too strong sunning (especially thru in hot countries). Make sure hens have a shaded zone on their course.

Irregular shell

This includes the irregular, tough ends or with asperities.

These problems are noted especially in old hens. Otherwise, it can also be the sign of a disease; it is better to consult a veterinarian.

White eggs

These are small eggs without yolk. This happens when a young pullet starts laying. It is not important and can be ignored unless the pullet continue to lay such eggs. This may also happen to old hens having undergone a sudden shock.

Greenish yolks

The presence of nipples or certains herbs can make turn the yolk greenish. Check the grazing ground and rake if necessary.

Light and dark yolks

The yolks are naturally clearer in winter when the grass does not grow and there is nothing abnormal with that. Some prefer darker yolks thinking that this is associated with the concept of "more natural". You just have to know that a food additive is sufficient to make yolks darker; stockbreeders use them of course. Yolk is more intense when carrots, red corn and greenery is introduced in the food.

Depending on the country, the consumers prefer a more or less dark yolk. For example, the Germans prefer an egg yolk more orange than the French. To determine the color of an egg, the Roche company diffused a scale of color for egg yolks: 15 nuances between yellow and orange carrying numbers from 1 to 15. To avoid the problems inherent in the differences between analysts and lighting, Minolta developed a system comprising a colorimeter, a computation software and a calculator to measure the color of the yolk according to the Roche scale. Breeders just need to adapt the food of the poultry to the target public.

Double yolk

This often happens with large eggs. This is by no means a problem, except when incubating fertilized eggs. In this case, those eggs will be isolated.

In fact, 2 yolks are released in the oviduct at the same time (either an early ovulation or a delay of the yolk in its progression in the oviduct) and wrapped in a single shell. This can also be caused by a sudden shock.

Blood on the shell

Trails of blook can be found on the shell, either at the time of the exit of a very large egg or in a young pullet which starts to lay. This is the reason why it is recommended not to force on lighting as long as the laying did not start.

If there are more bloodstains, you may suspect the presence of red ascarids and treat if this is the case.

Blood in eggs

A little blood can escape from the ovarian follicle and is included without the albumen. This may be caused by a shock or stress and is arrange all alone.

If a hereditary tendency to this problem, it is necessary to cease employing them for the reproduction.

Soiled eggs

The solution with this problem is obvious. It is really important to maintain cleanliness in and in the neighbourhood of the nests. Frequently collect eggs.

Liquid albumen

This can occur when the weather is hot and more frequently with old hens.

If the problem persists, consult a veterinarian.

The labelling of eggs

In Wallonia, the only mentions authorized to be reproduced on egg packs concern:

• the type of breeding
• the category
• the weight category
• optional mentions

The type of breeding

• Eggs of Eghens raised out of battery
• Eggs of hens on perches
• Eggs of hens raised on the ground: 7 hens per m² of surface on the ground whose 1/3 at least covered with litter of chips, digs peat, straw, sand…
• Eggs of hens raised in the open air: the hens are high in a building with a density of 7 hens/m², but open on a grassy space of 1 hen by 2,5 m² and uninterrupted possibility of free course in the open air
• Eggs of hens raised in free course, the hens are high in a building with a density of 7 hens/m² but profiting from 10 m²/hen and uninterrupted possibility of free course in the open air
• Biological eggs: resulting from hens raised in the open air or in free course with a food made up of 80% of products coming from biological agriculture (maximum density of 7 hens per m²)

The category

There are 3 categories of eggs: A, B and C. Only category A is intended for consumers. The 2 others are intended for the industrial production of products containing eggs.

The weight category

There are 4 mentions of size:

• XL or very large: for eggs whose weight is higher than 73 g
• L or large: for eggs whose weight ranges between 63 and 73 g
• M or medium: for eggs whose weight ranges between 53 and 63 g
• S or small: for eggs whose weight is lower than 53 g

Optional mentions

The following mentions are optional :

• the Extra mention: announces very fresh eggs, they were laid for 9 days to the maximum, i.e. 7 days after packing.
• the mention A: announce that the eggs have been laid for more than 9 days and are thus a little less fresh. They can be consumed during 3 weeks. At the end of these 4 weeks, the egg must be downgraded and withdrawn from the sale.

• Functions Of Egg Parts

  1.	air cell		an empty space located at the large end of the egg; it is between the inner and outer shell membranes
  2.	Albumin		white part of egg, supplies protien to the developing embryo
  3.	Chalazae		fibrous structures at the ends of the yolk, aiding in centering the yolk within the white
  4.	class		aves
  5.	Domain for chicken		Eukarya
  6.	Eggshell		protective outer layer of the egg, composed of calcium carbonate
  7.	family		phasianidae
  8.	genus		gallus
  9.	germinal disc		small, circular, white spot on the surface of the yolk; it is where the sperm enters the egg.
  10.	Incubation period		21 days
  11.	inner shell membrane		thin membrane located between the outer shell membrane and the albumin
  12.	kingdom		animalia
  13.	order		galliformes
  14.	outer shell membrane		thin membrane located just inside the shell.
  15.	phylum		chordata
  16.	species		G. domesticus
  17.	subphylum		vertebrata
  18.	temperature range for incubator		99 degrees F to 102 degrees F
  19.	Vitelline membrane		The membrane surrounding the egg yolk
  20.	Yolk		supplies nutrients to developing embryo.

  
  

Functions Of Egg Parts

1.

air cell

an empty space located at the large end of the egg; it is between the inner and outer shell membranes

2.

Albumin

white part of egg, supplies protien to the developing embryo

3.

Chalazae

fibrous structures at the ends of the yolk, aiding in centering the yolk within the white

4.

class

aves

5.

Domain for chicken

Eukarya

6.

Eggshell

protective outer layer of the egg, composed of calcium carbonate

7.

family

phasianidae

8.

genus

gallus

9.

germinal disc

small, circular, white spot on the surface of the yolk; it is where the sperm enters the egg.

10.

Incubation period

21 days

11.

inner shell membrane

thin membrane located between the outer shell membrane and the albumin

12.

kingdom

animalia

13.

order

galliformes

14.

outer shell membrane

thin membrane located just inside the shell.

15.

phylum

chordata

16.

species

G. domesticus

17.

subphylum

vertebrata

18.

temperature range for incubator

99 degrees F to 102 degrees F

19.

Vitelline membrane

The membrane surrounding the egg yolk

20.

Yolk

supplies nutrients to developing embryo.