Showing posts with label Animals. Show all posts
Showing posts with label Animals. Show all posts
Broilers All about
Broilers are chickens (Gallus
gallus domesticus) bred and raised specifically formeat production.[1] Chickens
are one of the most common and widespread domestic animals, and with a population of 19 billion
in 2011,[2] there
are more chickens in the world than any other species of bird.
Typical broilers have white feathers and yellowish skin. Most commercial
broilers bred for meat reach slaughter weight at between 5 to 7 weeks of age,
although slower growing strains reach slaughter weight at approximately 14
weeks of age. Because of this young age, much of their behaviour and physiology
is that of an immature bird. Broilers and egg laying hen are
the same species and share many characteristics, however, due to the rapid
growth and selection for enlarged breast muscles, broilers are susceptible to
different welfare concerns, particularly skeletal. Broilers are usually grown
as mixed-sex flocks in large sheds under intensive conditions, but some strains
can be grown as free-range flocks.
Domestication and modern breeding[edit]
The traditional poultry farming view of the
domestication of the chicken is stated in Britannica (2007):
"Humans first domesticated chickens of Indian origin for the purpose of cockfighting in
Asia, Africa, and Europe. Very little formal attention was given to egg or meat
production..."[3]
Before the development of modern commercial
meat breeds (cows, chickens, etc.) broilers consisted mostly of young male
chickens (cockerels) which were culled from farm flocks. Pedigree breeding
began around 1916.[4] Magazines
for the poultry industry existed at this time.[4][5] A hybrid variety
of chicken was
produced from a cross of a male of a naturally double-breastedCornish strain
and a female of a tall, large-boned strain of white Plymouth Rocks.[6] This
first attempt at a hybrid meat breed was introduced in the 1930s and became
dominant in the 1960s. The original cross was plagued by problems of low
fertility, slow growth, and disease susceptibility, and modern broilers have
gradually become very different from the Cornish/Rock hybrid.
As an example, Shaver (originally a breeder
of egg-layers, today part of Hendrix) began gathering breeding stock for a
broiler program in 1950. Besides the breeds normally favoured, Cornish Game,
Plymouth Rock, New Hampshire, Langshans, Jersey Black Giant and Brahmas breeds
were included. A white feathered female line was purchased from Cobb (a
competitor). A full scale breeding program was commenced in 1958, with
commercial shipments in Canada and the US in 1959 and in Europe in 1963.[7]
As a second example, colour sexing broilers
was proposed by Shaver in 1973. The genetics were a based on the company's
breeding plan for egg-layers which had been developed in the mid-1960s. The
difficulty facing the breeders of the colour-sexed broiler is that the end
product must be white-feathered by slaughter age. After 12 years (1985)
accurate colour sexing without compromising economic traits was achieved.[7]
General biology[edit]
Modern commercial broilers, for example, Cornish crosses or Cornish-Rocks[citation needed],
are specially bred for large scale, efficient meat production and although they
are the same species, grow much faster than egg laying hens or traditional dual purpose breeds.
They are noted for having very fast growth rates, a high feed conversion ratio,
and low levels of activity. Broilers often reach a slaughter weight of four to
five pounds (dressed) in only five weeks,[6] (another
source indicates six to seven weeks as typical)[8] although
more slow growing free-range and organic strains reach slaughter weight at 12
to 16 weeks of age. As a consequence, their behaviour and physiology are those
of immature birds rather than adults. Typical broilers have white feathers and
yellowish skin. Recent genetic analysis has revealed that at least the gene for
yellow skin was incorporated into domestic birds through hybridization with the Grey Junglefowl (G.
sonneratii).[9] Modern
crosses are also favorable for meat production because they lack the typical
"hair" which many breeds have that necessitates singeing after
plucking. Both male and female broilers are reared for their meat.
Behaviour[edit]
Because broiler chickens are the same species
as egg laying hens, their behavioural repertoires are initially similar, and
also similar to those of other gallinaceous birds.
However, broiler behaviour is modified by the environment and alters as the
broilers’ age and bodyweight rapidly increase. For example, the activity of
broilers reared outdoors is initially greater than broilers reared indoors, but
from six weeks of age, decreases to comparable levels in all groups.[10] The
same study shows that in the outdoors group, surprisingly little use is made of
the extra space and facilities such as perches – it was proposed that the main
reason for this was leg weakness as 80 per cent of the birds had a detectable gait abnormality at seven weeks of age.
There is no evidence of reduced motivation to extend the behavioural
repertoire, as, for example, ground pecking remained at significantly higher
levels in the outdoor groups because this behaviour could also be performed
from a lying posture rather than standing.
Broiler breeders, i.e. males and females
reared to fertilise and
lay the eggs of the offspring reared for food, perform similar mating behaviour
to other chicken types. They exhibit male-male aggression, male-hen aggression,
hen-hen aggression, male waltzes, hen crouches, attempted hen mounts,
completed hen mounts, attempted hen matings, and completed hen matings. These
behaviours are seen less often and may not be exhibited as vigorously as
observed in other chicken types.[11] Examining
the frequency of all sexual behaviour shows a large decrease with age,
suggestive of a decline in libido.
The decline in libido is not enough to account for reduced fertility in
heavy cocks at 58 weeks and is probably a consequence of the large bulk or theconformation of
the males at this age interfering in some way with the transfer of semen during copulations which otherwise look normal.[12]
Physiology
Nociceptors which
respond to noxious stimulation have been identified and physiologically
characterised in many different part of the body of the chicken including the beak,
mouth, nose, joint capsule and
scaly skin. Stimulation of these nociceptors produces cardiovascular and behavioural
changes consistent with those seen in mammals and are indicative of pain
perception. Physiological and behavioural experiments have identified the
problem of acute pain following beak trimming in
chicks, shackling, and feather pecking and
environmental pollution.[13]
Feeding
and feed conversion[edit]
Chickens are omnivores and
modern broilers are given access to a special diet of high protein feed,
usually delivered via an automated feeding system. This is combined with
artificial lighting conditions to stimulate growth and thus the desired body
weight is achieved in four to eight weeks, depending on the approximate body
weight required by the processing plant.
In the U.S. in 2011, the average feed conversion ratio of a broiler was 1.91 pounds of feed per
pound of liveweight. In 1925 the figure was 4.70.[14]
World production and consumption[edit]
Consumption of
broilers is surpassing that of beef in industrialized countries. Demand in Asia
is rising. [15]
Ayam Cemani in a closed house broiler farm
In 2003, approximately 42 billion broilers
were produced, of which 80% were descended from primary stock produced by three
companies: Aviagen, Cobb-Vantress,
and Hubbard Farms.[where?][16] More
recent data indicate that 82.9 million metric tonnes of broiler meat will be
produced in 2012.[17]
Broilers are sometimes reared on a grass
range using a method called pastured poultry, as developed by Joel Salatin and
promoted by the American Pastured Poultry Producers Association.[18] Commercial free-range broiler flocks are now common-place in Europe.[citation needed]
Industry structure[edit]
The broiler production process is very much
an industrial one. There are several distinct components of the broiler supply
chain.[19]
Primary
breeding sector[edit]
The "primary breeding sector"
consists of companies that breed pedigree stock. Pedigree stock ("pure
line") is kept on high level biosecure farms. Their eggs are hatched in a
special pedigree hatchery and their progeny then goes on to the great
grandparent (GGP) and grandparent (GP) generations. These eggs would then go to
a special GP hatchery to produce Parent Stock (PS) which passes to the
production sector.[19]
In 2006, out of an estimated world population
of 18 billion poultry, about 3% are breeding stock.[19] The
US supplied about 1/4 of world GP stock.[19]
Worldwide, the primary sector produced 417
million parent stock (PS) per year.[20]
A single pedigree-level hen might have 25000
parent stock bird descendents, which in turn might produce 3 million broilers.[21]
Numerous techniques are used to assess the
pedigree stock. For example, birds might be examined with ultrasound or x-rays
to study the shape of muscles and bones. The blood oxygen level is measured to
determine cardiovascular health. The walking ability of pedigree candidates is
observed and scored.[4]
The need for high levels of R&D spending
prompted consolidation within the primary breeder industry. By the late 2000s
only three sizable breeding groups[20] remained:
·
Aviagen
(with the Ross, Arbor Acres, Indian River and Peterson brands)
·
Cobb-Vantress
(with the Cobb, Avian, Sasso and Hybro brands), and
·
Groupe
Grimaud (with the Hubbard and Grimaud Frere brands).
In the UK, 2 international firms supply about
90% of the parent stock.[22]
Due to the high levels of variation in the
chicken genome, the industry has not yet reached biological limits to improved
performance.[20]
The full chicken genome was published in Nature, in December 2004. Today, all primary
breeding groups are investing heavily ingenomics research.
This research mostly focuses on understanding the function and effect of genes already present in the breeding
population. Research into transgenics — removing genes or artificially moving
genes from one individual or species to another — has fewer prospects of
gaining favor among consumers.[20]
Broiler
breeder (Parent Stock) farms[edit]
Broiler breeder farms raise parent stock
which produce fertilized eggs. A broiler hatching egg is never sold at stores
and is not meant for human consumption.[23] The
males and females are separate genetic lines or breeds.[22] The
chicks they produce will therefore be hybrids or
'crosses'. Since the birds are bred mainly for efficient meat production,
producing eggs can be a challenge.[24] In
Canada, the average producer houses 15,000 birds that begin laying hatching
eggs at 26 weeks of age. Each bird will lay about 150 hatching eggs for the
next 34 to 36 weeks. This cycle is then repeated when the producer puts another
flock of 26 week-old birds into his barns to begin the process again. As a
general rule, each farmer produces enough broiler hatching eggs to supply
chicks for 8 chicken producers.[25] (Other
sources indicate a parent hen will lay about 180 eggs in 40 week production
period.)[26]
Generally, parent flocks are either owned by
integrated broiler companies or hatcheries or are contracted to them on a
long-term basis.[22]
Broiler breeder growing is typically a
two-stage process. Parent stock purchased from a primary breeder is delivered
as day old. Most are first placed with on specialist rearing houses or starter farms until approximately
18 weeks of age.[22] The
starter farm has the specialized brooding equipment to raise the chicks.
Rearing
House[edit]
Florida chicken house.
A typical rearing house (also called a shed
or barn) design for Alabama-like climate (100 °F (38 °C) in summer
and 20 °F (−7 °C) in winter):[27]
·
40
by 400 feet (12 m × 122 m) size, single storey.
·
11,000
bird capacity (about 1.4 sq ft (0.13 m2) per bird)
·
Ceiling
is insulated
·
Exterior
curtain side walls.
·
A
"minimum ventilation" system is required for the heating period to
provide a certain amount of fresh air.
·
A
separate "tunnel ventilation" system with evaporative pad
cooling is desired
(minimum wind speed is 400 fpm) for hot weather in the later stage of the
bird's growth.
·
Air
inlets may be automatically adjusted.
·
A
negative ventilation system helps keep dirt and dust out of egg storage areas.
·
The
entire house may be heated, or individual "brooders" may be used.
·
The
floor is flat. There are no "slats" or "pits" for manure.
There are no cages, and no nests. "Litter" (shavings or straw) covers
the floor. When the chicks are introduced temporary barriers are used to keep
them close to the heated areas.
·
"Black-out"
design to keep out external light, so the day-night cycle can be controlled.
·
An
automatic timer-controlled lighting system. Dimmers allow
light intensity to be adjusted.
·
Automatic
feeders to distribute feed. Typically this consists of an endless chain in a
trough[28] or with individual pans.[29] Asilo or bin outside provides storage.
·
Automatic
drinkers provide water. There are several different designs, with
"nipples" or "round" drinkers being popular.[30]
·
Feeders
and drinkers are height adjusted as the birds grow, and can be raised on chains
or wires to allow cleanout of the barn.
Chicks require warm air temperatures, which
is reduced as the birds mature:
Age
|
Brooder Temperature
|
Whole-House Heating
Temperature
|
0 days
|
34–35 °C
|
31–32 °C
|
14 days
|
31–32 °C
|
24–25 °C[31]
|
Chicks might be debeaked at
7–10 days age.[31] During
rearing, bird weight is carefully monitored, as an over-weight bird will be a
poor egg producer. The feed mix will be adjusted to meet nutritional needs at
each stage. Feed might be restricted to control body weight, for example with
"skip a day" feeding, or feeding 5 days out of 7. A vaccination
program is carried out, which ensures the longevity of the parent stock, and
the immunity may be passed to the broiler progeny. Males (cockerels) and
females (pullets), are usually raised separately.
Laying
House[edit]
The birds are then moved to broiler breeder laying houses or production barns. The birds are
typically placed into crates,[32] and
transported by truck to a separate facility. Males and females are raised
together at this point. Outwardly the laying house will resemble the rearing
house. Inside, about one-half of the floor might consist of raised 'slats.'[31][33] During
the production run, manure will drop through the slats and accumulate in the
pit underneath the slats. The birds are not generally caged, especially since
the roosters must
mate with the hens to fertilize the
eggs. Nests are provided for laying hens. Both automatic and manual(example) nesting
systems exist. Manual nests are usually stuffed with straw or shavings and eggs
are hand-collected. Automatic systems usually have a plastic carpet lining,
with an belt for egg collection.[31] Careful
layout and attention to bird behavior is required to avoid 'floor eggs'.
Depending on breed, egg production starts at
24–26 weeks of age. Production percentage (daily eggs per hen) climbs rapidly
to a peak of 80–85% at 29–32 weeks, and then gradually declines with age.
Hatchability tends to peak (at perhaps 90%) somewhat later than production at
34–36 weeks.[34] Overall
flock production will decline as mortality reduces the size of the flock.
When the rooster mates with the hen, sperm
enter the hen's oviduct and are stored within sperm storage glands. These
glands can store more than half a million sperm, and sperm can remain viable
for up to 3 weeks. However, a hen will have maximum fertility for only about 3
to 4 days after one mating. Therefore, the male-to-female ratio in a flock must
be enough to ensure mating of every hen every 3 days or so.[26] To
maintain fertility, younger roosters may be introduced as the flock ages.
Eggs are collected a minimum of twice a day,
and usually more frequently. Cracked or dirty eggs are separated, as they are
not suitable for hatching. Undersized, over-sized or double-yolk eggs are also
unsuitable. The eggs might be disinfected byfumigation, are packed in 'flats' or trays, placed
in wheeled trolleys, and stored in a cool (15-18C) climate-controlled area. The
egg packing room and storage rooms are kept segrated to reduce contamination.
The trolleys are delivered by truck to a hatchery perhaps twice a week.
At the end of the production cycle, the birds
are called "spent fowl". Disposal of spent fowl may be a problem as
consumer demand for them is poor.[35]
Hatcheries[
Five day old broiler
strain Cornish-Rock chicks.
Hatcheries take
the fertilized eggs, incubate them,
and produce day old broiler chicks.
Incubation takes about 21 days, and is often
a two-step process. Initial incubation is done in machines known
as setters. A modern
setter is the size of a large room, with a central corridor and racks on either
side. Eggs are held relatively tightly (large end up) in trays, which are stored
in the racks. Inside the setter, temperature and humidity are closely
maintained. Blowers or fans circulate air to ensure uniform temperature, and
heating or cooling is applied as needed by automated controls. The racks pivot
or tilt from side to side, usually on an hourly basis.[36] As
an example, one commercial machine can hold 95,040 eggs and measures about 3.7
metres wide by 6.6 metres deep.[37] Setters
often hold more than one hatch, on a staggered hatch-day basis, and operate
continuously. The setter phase lasts about 18 days.[38]
On or about day 18, the eggs are removed from
the setters and transferred to hatchers.
These machines are similar to setters, but have larger flat-bottom trays, so
the eggs can rest on their sides, and newly hatched chicks can walk. Having a
separate machine helps keep hatching debris out of the setter. The
environmental conditions in the hatcher are optimized to help the chicks hatch.
As a commercial example, a large hatcher has capacity for 15,840 eggs, and
measures about 3.3 metres by 1.8 metres.[39]
Some incubators are single-stage (combining
setter and hatcher funcations), and entire trolleys of eggs can be rolled in at
one time.[40] One
advantage of single-stage machines is that they are thoroughly cleaned after
each hatch, whereas a setter is rarely shutdown for cleaning. The single-stage
environment can be adjusted for eggs from different producing flocks, and for
each step of the hatch cycle. The setter environment is often a compromise as
different egg batches are in the machine at one time.[citation needed]
On hatch day (day 21), the trays are removed
("pulled") from the hatchers, and then the chicks are removed from
the trays. Chicks are inspected, with the sickly ones being disposed of. Chicks
may be by vaccinated, sorted by sex, counted, and placed in
chick boxes.(Example1) (Example2) Stacks
of chick boxes are loaded into trucks for transport, and arrive at the broiler
farm on the same day. Specialized climate-controlled trucks are typically used,
depending on climate and transport distance.[41]
Chick sexing is
optionally done to improve uniformity – since males grow faster, the weights
are more uniform if males and females are raised separately. The birds are bred
so that males and females have unique feather patterns or color differences.
Unlike egg-laying poultry, males are not culled.
Typical hatchability rate in Canada in 2011
was 82.2%.[42] (i.e.
82.2% of eggs set for incubation produced a saleable chick). A UK source
estimates 90% hatchability.
Broiler
farms[edit]
The chicks are delivered to the actual
broiler Grow-Out farms.
![[icon]](http://en.wikipedia.org/wiki/File:Wiki_letter_w_cropped.svg){kind=small} |
This section
requires expansion. (June
2012)
|
In the US, houses may be up to 60' x 600'
(36000 sq.ft.).[43] One
2006 magazine survey reported a desired 67 foot wide house, with the average
'standard' new house being 45' x 493', with largest being 60' x 504'.[44] One
farm complex may have several houses.
In Mississippi, typical farms now have four
to six houses with 25,000 birds per house. One full-time worker might manage
three houses. On average, a new broiler house is about 500 feet long by 44 feet
wide and costs about $200,000 equipped.[45]
When the birds are full-grown, they are
caught (perhaps with a Chicken harvester) placed in crates, and
transported by truck to a processing plant.
Broiler chickens kept
outside near a chicken shop in India
Because of their efficient meat conversion,
broiler chickens are also popular in smallfamily farms in
rural communities, where a family will raise a small flock of broilers.[citation needed]
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