Name: ニワトリの科学。 (THE SCIENCE OF CHICKENS.)
Uploaded: 2021-01-14T10:55:54.000Z
Duration: 10 min 50 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Their meteoric rise in number over time makes them 70% of all birds alive right now on Earth,

23 billion or so, all born for their meat, or the eggs they produce.

Together with turkeys, they are 99% of all land animals slaughtered for food in the United

States, with an estimated 55 billion killed worldwide yearly.

That is 5,400,000 every hour or around 1,500 every second.

So, what prompted humans to produce and kill so many chickens?

Did you know they are a lot smarter than we think and have the ability to dream like humans?

Do you know how the chickens we consume are raised and treated?

The truth is no yolk; let's find out now.

Chickens (Gallus domesticus) are domestic birds that cannot fly.

There are over 150 different breeds that come in various colours, patterns, and sizes.

Let's not get into what came first - the chicken or egg; let's start by looking at

the amazing way a chick develops and is born from an egg….

It takes 24 to 26 hours for a hen to construct an egg.

Once a yolk is fully developed, it is released from the ovary into the oviduct, which is

The first stop is the infundibulum, which, in addition to being fun to say, is a short,

muscular portion of the oviduct which engulfs the ovum, or yolk, that is released from the

The ovum remains in the infundibulum for 15 to 18 minutes, and it is here where fertilisation

would occur if the hen mated with a rooster.

However, eggs sold for human consumption are not fertilised.

The next stage occurs in the magnum, the largest section of the oviduct at 13 inches long.

The yolk stays in the magnum for 3 hours while the albumen, or “egg white,” is added.

The third stop is the isthmus, where the inner and outer shell membranes are added over a

The longest stage of egg production occurs in the shell gland or uterus.

This is where the shell is deposited around the egg, which takes 20 plus hours.

Eggshells are mostly made of calcium carbonate, and for each shell produced, the hen must

lose approximately 10% of the calcium stored in her bones.

The last stop in egg production is the vagina.

This is where a coating of mucus is added to the shell.

The vagina pushes the egg out through the vent or cloaca - the shared exit through which

If the egg was fertilized, a baby chicken hatches after about 21 days and is known as

After 16 weeks, they are usually fully developed adults.

Males are known as roosters and females as hens.

Chickens are surprisingly intelligent animals.

They can perceive time intervals, anticipate future events, recall the location of a hidden

object, and recognise over 100 individual faces, not only of fellow chickens but of

They also pass down knowledge from generation to generation.

Chickens are caring and sensitive animals who feel joy, loneliness, frustration, fear,

They experience rapid eye movement, or REM, during sleep; an indication that they dream

akin to humans, and that their minds may be wandering far from the walls of the factory

Mother hens begin communicating with their chicks before they even hatch.

While the babies are still inside their shells, the mother hen clucks softly to them, and

Chickens also purr when they're petted, like cats.

This communication is done with more than 24 vocalisations, and each one has a distinct

The history of chickens is similarly fascinating.

A comparison of the amino-acid sequence from T-Rex collagen showed that it shared a remarkable

The T-Rex is actually more closely related to chickens than alligators.

Chickens were first domesticated from a wild form called red junglefowl, in Southeast Asia

By about 2000 BCE, they appeared at Mohenjo-Daro in the Indus Valley and, from there, they

In 1944, Howard C. Pierce, the poultry research director for the A&P Food Stores supermarket

chain, told a poultry meeting in Canada that someone needed to develop a larger chicken

By the next summer, his wish ignited the Chicken of Tomorrow contest, organised by the USDA,

with the backing of A&P and the support of every significant poultry and egg organisation

The aim of this contest was to breed a bird chunky enough to feed a whole family – a

This event led not to just the enhanced birds but a new economy their developers hoped to

create: one where the Chicken of Tomorrow would be the dominant meat in markets.

As a result, it was discovered that by using feed laced with antibiotics, chickens could

grow twice as fast, prompting 80% of antibiotics sold in the United States to be utilized for

Over the last decades, genetic engineering and technology have produced even bigger chickens,

In 2004, a team of geneticists mapped the chicken genome, which provided an opportunity

to study how a millennia of domestication can alter a species.

The researchers' findings include mutations in a gene designated TBC1D1, which regulates

glucose metabolism, and found that this gene could be manipulated causing chickens to become

Another mutation resulting from selective breeding is in the TSHR, the thyroid-stimulating

In wild animals, this gene coordinates reproduction with day length, confining breeding to specific

The mutation disables this gene, and manipulates chickens into breeding and laying eggs all

Both of these mutations made the chicken even more attractive to meat producers.

Chickens raised for food fall into two categories.

Broiler chickens, who are raised for meat and egg laying chickens.

These chickens have been rendered ill and unfit by genetic manipulation, poor diets,

drugs, and antibiotics, as well as the toxic air and bedding in the sheds where they live.

Excretory ammonia fumes often become so strong that the birds develop a blinding eye disease

called ammonia burn, where afflicted birds rub their hurting eyes with their wings

Modern broiler chickens have skeletons that are significantly bigger than their wild ancestor