Animal anatomy and physiology

Sex and Age Characteristics of Poultry

Poultry are domesticated birds that are bred specifically to provide meat and eggs for

human consumption. They include fowl, ducks, geese, turkeys and guinea fowl.

Fowl are the main source of meat and eggs for consumption. They all come from

two generic flocks:

(1) Chicken or broiler. Bred for poultry meat production. These birds are specifically

bred from the Light Sussex cross for rapid weight gain, white flesh, long body

and good breast-meat development. They can be recognised by their white

feathers, some of which will remain on the dressed bird. They get the name broiler

from the broiler houses in which they are bred. A broiler house can hold up to

20000 or more birds. They are only 6–8 weeks old at the time of slaughter.

(2) Hen. Although sold for meat as hens or boiling fowl, they are specifically bred

for their egg production capabilities. They are from a Rhode Island Red cross and

can be recognised by their red-brown feathers. They are at least 18 months old

and display all the secondary sexual and ageing characteristics (see below).

Identification and ageing of poultry

Fowl

It is important to know the differences between young chickens bred for their meat and

older birds bred for their egg production with their meat value being of secondary

importance for the producer. The following are the main identification features.

Head

The fowl head has two distinct features which all fowl display. First, they have

the comb. This is a fleshy serrated crest beginning at the base of the top beak and

running backwards over the crown of the head. Second, they have wattles, which are

loose, fleshy, pouch-like bags. One wattle is situated underneath each side of the lower

beak.

The hens, being much older, have developed their secondary sexual characteristics.

Old: Comb well developed and is a bright red colour. Wattles well developed. Beak

hard and rigid. 

Young: Comb poorly developed and is a much lighter colour. Wattles small and

underdeveloped. Beak soft and pliable.

Skin

Old: Rough and feather follicles easily visible, especially on the legs. Hair-like

feathers (filoplumes) visible, especially on the back of the bird.

Young: Smooth, relatively flawless. Only down feathers visible.

Body

Old: Breast bone protrudes sharply, giving a characteristic hatchet-shaped breast.

Distended abdomen with large amounts of deposited fat. Breast bone has fully ossified

and is hard. Vent is extended and large to allow egg laying.

Young: Broad, well-fleshed breast. No distension of the abdomen. End of breast bone

still cartilage (xyphoid) and is soft and pliable. Vent is small.

Legs and feet

Old: Leg scales hard and coarse. Larger feet. Claws large and rigid.

Young: Leg scales soft and smooth. Small feet. Claws shorter and softer.

In addition, the intended use for the bird will be indicated by the colour of any feathers.

White feathers denote a bird intended for meat production; red/brown feathers

denote an egg-laying bird.

Turkey

In turkeys it is important to be able to identify the differences between the male and

female rather than the age, as in fowl.

The turkey, like the fowl, has two distinct features on its head and neck. First, at the

base of the upper beak is a fleshy, finger-like projection called a snood. Second, turkeys

have numerous wattles on the neck which resemble small fleshy pouches. The head and

neck of a turkey have no feathering to cover the skin.

Overall appearance

Male: Longer neck and legs and greater overall size.

Female: Shorter and more compact.

Sexual characteristics

Male: Has a ‘brush’, which is a small patch of coarse black hairs at the base of the

neck. Snood is longer and thicker. Wattles more developed and the neck skin has a more

wrinkled appearance. Older males have spurs on the legs. No feathers seen beyond the

neck wattles, only skin.

Female: No ‘brush’ evident. Snood smaller. Less well-developed wattles and

smoother neck skin. Only spur buds visible. Line of feathers go up the back of the neck

to the base of the skull.

Terminology

A number of terms are given to poultry, depending on the age and sex of the bird at

the time of slaughter. The following terminology is applied to fowl.

Chicken or broiler

This is a young male or female domestic fowl. It has not developed any secondary

sexual characteristics as it is usually slaughtered between 6 and 8 weeks of age. It

weighs about 2 kg (4 lb) and is suitable for roasting.

Petit poussin or poussin

This is an even younger chicken which is slaughtered when weighing about 0.3 kg

(0.5 lb). It is also suitable for roasting.

Roaster

This is an older chicken, being up to 8 months of age and weighing about 2.7 kg (6 lb).

Broiler breeder or cob

This is a sexually mature female which has laid fertilised eggs to produce more chickens

or broilers. They will be about 18 months of age and weigh about 2.7 kg (6 lb).

Normally roasted.

Hen or boiling fowl

This is an egg-laying female bird which has completed at least one egg-laying season.

It will be about 18 months of age and has developed all the secondary sexual characteristics.

The meat is not tender enough to roast and is boiled to cook it.

Capon

This was a male chicken of 15–16 weeks of age which had been neutered by

hormonal implant or surgery. It is now illegal to produce such a bird. However, a similar

type of bird is produced without being neutered; it is called a capon-style or heavy

roaster.

Cockerel

This is a sexually mature male domestic fowl. Cockerels are not used for human

consumption.

Pullet

This is a young hen.

There are fewer categories of turkey as they are older when slaughtered. This is to give

them the time necessary to grow to the larger size and weight demanded by the consumer.

The following terminology is applied to turkeys. 

Stag

This is a male turkey.

Hen

This is a female turkey.

Poult

This is a young turkey. The term can also be used for young domestic fowl

Anatomy of the Fowl

Skin

The skin is composed of two layers, the epidermis and the dermis. It is usually

creamy white and thin. Unlike mammalian skin it has few sebaceous and no

sweat glands, but it does have a uropygeal or oil gland not present in mammals. This

in poultry is small, about 5 mm in diameter, but is much larger in water birds. It lies

on the dorsal surface of the tail and has two lobes producing a yellow ceruminous

material, which is used in preening the feathers. 

Other accessory structures of the skin are the claws, beaks, wattles, combs and ear lobes. The fold of skin filling in the angle between the humerus and radius, i.e. between the body and the wing, is called the patagium.

In most areas the skin is covered with feathers, which arise from feather follicles that

project into the dermis. Feathers are composed entirely of a horny substance called

keratin. They fall into three main categories:

(1) Contour feathers.

(2) Downy feathers.

(3) Filoplumes, which are hair-like.

Contour feathers are arranged in rows within areas called pterylae. These areas are

separated by non-feathered areas called apteria. The largest contour feathers are the

flight feathers of the wings and the feathers of the tail.

A typical contour feather (Fig.1) consists of a central shaft or rachis; a lower

part, the calamus or quill; and an upper part or vane. At the end of the quill is a small

opening, the inferior umbilicus. During growth it connects with a papilla of the dermis.

The quill is rounded and almost transparent and contains a series of scales. At the junction

of the quill and axis is another small opening, the superior umbilicus, from which

arises a small additional feather, the afterfeather. The axis of the vane, the rachis, has

a central groove, and is solid, tapering and flexible.

The vane consists of filaments or barbs arising from each side of the rachis at 45°

and in turn smaller filaments or barbules project distally and proximally also at about

45°. The result is that the barbules cross each other at an angle of about 90°.

Hooklets from each set of barbules engage with recesses in corresponding barbules.

Fig. 1 Contour feather.

This interlocking gives firmness to the vane. The contour feathers can be

raised or depressed by muscles attached to the feather follicles.

Feathers are extremely light in spite of their complex structure and size.

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