Domestic sheep (Ovis aries) are quadrupedal,
ruminant mammals typically kept as livestock.
Like most ruminants, sheep are members of
the order Artiodactyla, the even-toed ungulates.
Although the name sheep applies to many species
in the genus Ovis, in everyday usage it almost
always refers to Ovis aries.
Numbering a little over one billion, domestic
sheep are also the most numerous species of
sheep.
An adult female sheep is referred to as a
ewe (), an intact male as a ram or occasionally
a tup, a castrated male as a wether, and a
younger sheep as a lamb.
Sheep are most likely descended from the wild
mouflon of Europe and Asia.
One of the earliest animals to be domesticated
for agricultural purposes, sheep are raised
for fleece, meat (lamb, hogget or mutton)
and milk.
A sheep's wool is the most widely used animal
fiber, and is usually harvested by shearing.
Ovine meat is called lamb when from younger
animals and mutton when from older ones in
Commonwealth countries, and lamb in the United
States (including from adults).
Sheep continue to be important for wool and
meat today, and are also occasionally raised
for pelts, as dairy animals, or as model organisms
for science.
Sheep husbandry is practised throughout the
majority of the inhabited world, and has been
fundamental to many civilizations.
In the modern era, Australia, New Zealand,
the southern and central South American nations,
and the British Isles are most closely associated
with sheep production.
Sheepraising has a large lexicon of unique
terms which vary considerably by region and
dialect.
Use of the word sheep began in Middle English
as a derivation of the Old English word scēap;
it is both the singular and plural name for
the animal.
A group of sheep is called a flock, herd or
mob.
Many other specific terms for the various
life stages of sheep exist, generally related
to lambing, shearing, and age.
Being a key animal in the history of farming,
sheep have a deeply entrenched place in human
culture, and find representation in much modern
language and symbology.
As livestock, sheep are most often associated
with pastoral, Arcadian imagery.
Sheep figure in many mythologies—such as
the Golden Fleece—and major religions, especially
the Abrahamic traditions.
In both ancient and modern religious ritual,
sheep are used as sacrificial animals.
== History ==
The exact line of descent between domestic
sheep and their wild ancestors is unclear.
The most common hypothesis states that Ovis
aries is descended from the Asiatic (O. orientalis)
species of mouflon.
Sheep were among the first animals to be domesticated
by humankind (although the domestication of
dogs may be over 20,000 years earlier); the
domestication date is estimated to fall between
11,000 and 9,000 B.C in Mesopotamia.
The rearing of sheep for secondary products,
and the resulting breed development, began
in either southwest Asia or western Europe.
Initially, sheep were kept solely for meat,
milk and skins.
Archaeological evidence from statuary found
at sites in Iran suggests that selection for
woolly sheep may have begun around 6000 BC,
and the earliest woven wool garments have
been dated to two to three thousand years
later.Sheep husbandry spread quickly in Europe.
Excavations show that in about 6000 BC, during
the Neolithic period of prehistory, the Castelnovien
people, living around Châteauneuf-les-Martigues
near present-day Marseille in the south of
France, were among the first in Europe to
keep domestic sheep.
Practically from its inception, ancient Greek
civilization relied on sheep as primary livestock,
and were even said to name individual animals.
Ancient Romans kept sheep on a wide scale,
and were an important agent in the spread
of sheep raising.
Pliny the Elder, in his Natural History (Naturalis
Historia), speaks at length about sheep and
wool.
European colonists spread the practice to
the New World from 1493 onwards.
== Characteristics ==
Domestic sheep are relatively small ruminants,
usually with a crimped hair called wool and
often with horns forming a lateral spiral.
Domestic sheep differ from their wild relatives
and ancestors in several respects, having
become uniquely neotenic as a result of selective
breeding by humans.
A few primitive breeds of sheep retain some
of the characteristics of their wild cousins,
such as short tails.
Depending on breed, domestic sheep may have
no horns at all (i.e. polled), or horns in
both sexes, or in males only.
Most horned breeds have a single pair, but
a few breeds may have several.
Another trait unique to domestic sheep as
compared to wild ovines is their wide variation
in color.
Wild sheep are largely variations of brown
hues, and variation within species is extremely
limited.
Colors of domestic sheep range from pure white
to dark chocolate brown, and even spotted
or piebald.
Selection for easily dyeable white fleeces
began early in sheep domestication, and as
white wool is a dominant trait it spread quickly.
However, colored sheep do appear in many modern
breeds, and may even appear as a recessive
trait in white flocks.
While white wool is desirable for large commercial
markets, there is a niche market for colored
fleeces, mostly for handspinning.
The nature of the fleece varies widely among
the breeds, from dense and highly crimped,
to long and hairlike.
There is variation of wool type and quality
even among members of the same flock, so wool
classing is a step in the commercial processing
of the fibre.Depending on breed, sheep show
a range of heights and weights.
Their rate of growth and mature weight is
a heritable trait that is often selected for
in breeding.
Ewes typically weigh between 45 and 100 kilograms
(100 and 220 lb), and rams between 45 and
160 kilograms (100 and 350 lb).
When all deciduous teeth have erupted, the
sheep has 20 teeth.
Mature sheep have 32 teeth.
As with other ruminants, the front teeth in
the lower jaw bite against a hard, toothless
pad in the upper jaw.
These are used to pick off vegetation, then
the rear teeth grind it before it is swallowed.
There are eight lower front teeth in ruminants,
but there is some disagreement as to whether
these are eight incisors, or six incisors
and two incisor-shaped canines.
This means that the dental formula for sheep
is either 0.0.3.34.0.3.3 or 0.0.3.33.1.3.3
There is a large diastema between the incisors
and the molars.
In the first few years of life one can calculate
the age of sheep from their front teeth, as
a pair of milk teeth is replaced by larger
adult teeth each year, the full set of eight
adult front teeth being complete at about
four years of age.
The front teeth are then gradually lost as
sheep age, making it harder for them to feed
and hindering the health and productivity
of the animal.
For this reason, domestic sheep on normal
pasture begin to slowly decline from four
years on, and the life expectancy of a sheep
is 10 to 12 years, though some sheep may live
as long as 20 years.
Sheep have good hearing, and are sensitive
to noise when being handled.
Sheep have horizontal slit-shaped pupils,
with excellent peripheral vision; with visual
fields of about 270° to 320°, sheep can
see behind themselves without turning their
heads.
Many breeds have only short hair on the face,
and some have facial wool (if any) confined
to the poll and or the area of the mandibular
angle; the wide angles of peripheral vision
apply to these breeds.
A few breeds tend to have considerable wool
on the face; for some individuals of these
breeds, peripheral vision may be greatly reduced
by "wool blindness", unless recently shorn
about the face.
Sheep have poor depth perception; shadows
and dips in the ground may cause sheep to
baulk.
In general, sheep have a tendency to move
out of the dark and into well-lit areas, and
prefer to move uphill when disturbed.
Sheep also have an excellent sense of smell,
and, like all species of their genus, have
scent glands just in front of the eyes, and
interdigitally on the feet.
The purpose of these glands is uncertain,
but those on the face may be used in breeding
behaviors.
The foot glands might also be related to reproduction,
but alternative reasons, such as secretion
of a waste product or a scent marker to help
lost sheep find their flock, have also been
proposed.
=== Comparison with goats ===
Sheep and goats are closely related: both
are in the subfamily Caprinae.
However, they are separate species, so hybrids
rarely occur, and are always infertile.
A hybrid of a ewe and a buck (a male goat)
is called a sheep-goat hybrid (only a single
such animal has been confirmed), and is not
to be confused with the sheep-goat chimera,
though both are known as geep.
Visual differences between sheep and goats
include the beard of goats and divided upper
lip of sheep.
Sheep tails also hang down, even when short
or docked, while the short tails of goats
are held upwards.
Also, sheep breeds are often naturally polled
(either in both sexes or just in the female),
while naturally polled goats are rare (though
many are polled artificially).
Males of the two species differ in that buck
goats acquire a unique and strong odor during
the rut, whereas rams do not.
=== Breeds ===
The domestic sheep is a multi-purpose animal,
and the more than 200 breeds now in existence
were created to serve these diverse purposes.
Some sources give a count of a thousand or
more breeds, but these numbers cannot be verified,
according to some sources.
However, several hundred breeds of sheep have
been identified by the Food and Agriculture
Organization of the UN (FAO), with the estimated
number varying somewhat from time to time:
e.g. 863 breeds as of 1993, 1314 breeds as
of 1995 and 1229 breeds as of 2006.
(These numbers exclude extinct breeds, which
are also tallied by the FAO.)
For the purpose of such tallies, the FAO definition
of a breed is "either a subspecific group
of domestic livestock with definable and identifiable
external characteristics that enable it to
be separated by visual appraisal from other
similarly defined groups within the same species
or a group for which geographical and/or cultural
separation from phenotypically similar groups
has led to acceptance of its separate identity."
Almost all sheep are classified as being best
suited to furnishing a certain product: wool,
meat, milk, hides, or a combination in a dual-purpose
breed.
Other features used when classifying sheep
include face color (generally white or black),
tail length, presence or lack of horns, and
the topography for which the breed has been
developed.
This last point is especially stressed in
the UK, where breeds are described as either
upland (hill or mountain) or lowland breeds.
A sheep may also be of a fat-tailed type,
which is a dual-purpose sheep common in Africa
and Asia with larger deposits of fat within
and around its tail.
Breeds are often categorized by the type of
their wool.
Fine wool breeds are those that have wool
of great crimp and density, which are preferred
for textiles.
Most of these were derived from Merino sheep,
and the breed continues to dominate the world
sheep industry.
Downs breeds have wool between the extremes,
and are typically fast-growing meat and ram
breeds with dark faces.
Some major medium wool breeds, such as the
Corriedale, are dual-purpose crosses of long
and fine-wooled breeds and were created for
high-production commercial flocks.
Long wool breeds are the largest of sheep,
with long wool and a slow rate of growth.
Long wool sheep are most valued for crossbreeding
to improve the attributes of other sheep types.
For example: the American Columbia breed was
developed by crossing Lincoln rams (a long
wool breed) with fine-wooled Rambouillet ewes.
Coarse or carpet wool sheep are those with
a medium to long length wool of characteristic
coarseness.
Breeds traditionally used for carpet wool
show great variability, but the chief requirement
is a wool that will not break down under heavy
use (as would that of the finer breeds).
As the demand for carpet-quality wool declines,
some breeders of this type of sheep are attempting
to use a few of these traditional breeds for
alternative purposes.
Others have always been primarily meat-class
sheep.A minor class of sheep are the dairy
breeds.
Dual-purpose breeds that may primarily be
meat or wool sheep are often used secondarily
as milking animals, but there are a few breeds
that are predominantly used for milking.
These sheep produce a higher quantity of milk
and have slightly longer lactation curves.
In the quality of their milk, the fat and
protein content percentages of dairy sheep
vary from non-dairy breeds, but lactose content
does not.
A last group of sheep breeds is that of fur
or hair sheep, which do not grow wool at all.
Hair sheep are similar to the early domesticated
sheep kept before woolly breeds were developed,
and are raised for meat and pelts.
Some modern breeds of hair sheep, such as
the Dorper, result from crosses between wool
and hair breeds.
For meat and hide producers, hair sheep are
cheaper to keep, as they do not need shearing.
Hair sheep are also more resistant to parasites
and hot weather.With the modern rise of corporate
agribusiness and the decline of localized
family farms, many breeds of sheep are in
danger of extinction.
The Rare Breeds Survival Trust of the UK lists
22 native breeds as having only 3,000 registered
animals (each), and The Livestock Conservancy
lists 14 as either "critical" or "threatened".
Preferences for breeds with uniform characteristics
and fast growth have pushed heritage (or heirloom)
breeds to the margins of the sheep industry.
Those that remain are maintained through the
efforts of conservation organizations, breed
registries, and individual farmers dedicated
to their preservation.
== Diet ==
Sheep are exclusively herbivorous mammals.
Most breeds prefer to graze on grass and other
short roughage, avoiding the taller woody
parts of plants that goats readily consume.
Both sheep and goats use their lips and tongues
to select parts of the plant that are easier
to digest or higher in nutrition.
Sheep, however, graze well in monoculture
pastures where most goats fare poorly.
Like all ruminants, sheep have a complex digestive
system composed of four chambers, allowing
them to break down cellulose from stems, leaves,
and seed hulls into simpler carbohydrates.
When sheep graze, vegetation is chewed into
a mass called a bolus, which is then passed
into the rumen, via the reticulum.
The rumen is a 19- to 38-liter (5 to 10 gallon)
organ in which feed is fermented.
The fermenting organisms include bacteria,
fungi, and protozoa.
(Other important rumen organisms include some
archaea, which produce methane from carbon
dioxide.)
The bolus is periodically regurgitated back
to the mouth as cud for additional chewing
and salivation.
After fermentation in the rumen, feed passes
into the reticulum and the omasum; special
feeds such as grains may bypass the rumen
altogether.
After the first three chambers, food moves
into the abomasum for final digestion before
processing by the intestines.
The abomasum is the only one of the four chambers
analogous to the human stomach, and is sometimes
called the "true stomach".Other than forage,
the other staple feed for sheep is hay, often
during the winter months.
The ability to thrive solely on pasture (even
without hay) varies with breed, but all sheep
can survive on this diet.
Also included in some sheep's diets are minerals,
either in a trace mix or in licks.
Feed provided to sheep must be specially formulated,
as most cattle, poultry, pig, and even some
goat feeds contain levels of copper that are
lethal to sheep.
The same danger applies to mineral supplements
such as salt licks.
=== Grazing behavior ===
Sheep follow a diurnal pattern of activity,
feeding from dawn to dusk, stopping sporadically
to rest and chew their cud.
Ideal pasture for sheep is not lawnlike grass,
but an array of grasses, legumes and forbs.
Types of land where sheep are raised vary
widely, from pastures that are seeded and
improved intentionally to rough, native lands.
Common plants toxic to sheep are present in
most of the world, and include (but are not
limited to) cherry, some oaks and acorns,
tomato, yew, rhubarb, potato, and rhododendron.
==== Effects on pasture ====
Sheep are largely grazing herbivores, unlike
browsing animals such as goats and deer that
prefer taller foliage.
With a much narrower face, sheep crop plants
very close to the ground and can overgraze
a pasture much faster than cattle.
For this reason, many shepherds use managed
intensive rotational grazing, where a flock
is rotated through multiple pastures, giving
plants time to recover.
Paradoxically, sheep can both cause and solve
the spread of invasive plant species.
By disturbing the natural state of pasture,
sheep and other livestock can pave the way
for invasive plants.
However, sheep also prefer to eat invasives
such as cheatgrass, leafy spurge, kudzu and
spotted knapweed over native species such
as sagebrush, making grazing sheep effective
for conservation grazing.
Research conducted in Imperial County, California
compared lamb grazing with herbicides for
weed control in seedling alfalfa fields.
Three trials demonstrated that grazing lambs
were just as effective as herbicides in controlling
winter weeds.
Entomologists also compared grazing lambs
to insecticides for insect control in winter
alfalfa.
In this trial, lambs provided insect control
as effectively as insecticides.
== Behavior ==
=== Flock behavior ===
Sheep are flock animals and strongly gregarious;
much sheep behavior can be understood on the
basis of these tendencies.
The dominance hierarchy of sheep and their
natural inclination to follow a leader to
new pastures were the pivotal factors in sheep
being one of the first domesticated livestock
species.
Furthermore, in contrast to the red deer and
gazelle (two other ungulates of primary importance
to meat production in prehistoric times),
sheep do not defend territories although they
do form home ranges.
All sheep have a tendency to congregate close
to other members of a flock, although this
behavior varies with breed, and sheep can
become stressed when separated from their
flock members.
During flocking, sheep have a strong tendency
to follow and a leader may simply be the first
individual to move.
Relationships in flocks tend to be closest
among related sheep: in mixed-breed flocks,
subgroups of the same breed tend to form,
and a ewe and her direct descendants often
move as a unit within large flocks.
Sheep can become hefted to one particular
local pasture (heft) so they do not roam freely
in unfenced landscapes.
Lambs learn the heft from ewes and if whole
flocks are culled it must be retaught to the
replacement animals.Flock behaviour in sheep
is generally only exhibited in groups of four
or more sheep; fewer sheep may not react as
expected when alone or with few other sheep.
Being a prey species, the primary defense
mechanism of sheep is to flee from danger
when their flight zone is entered.
Cornered sheep may charge and butt, or threaten
by hoof stamping and adopting an aggressive
posture.
This is particularly true for ewes with newborn
lambs.In regions where sheep have no natural
predators, none of the native breeds of sheep
exhibit a strong flocking behavior.
==== Herding ====
Farmers exploit flocking behavior to keep
sheep together on unfenced pastures such as
hill farming, and to move them more easily.
For this purpose shepherds may use herding
dogs in this effort, with a highly bred herding
ability.
Sheep are food-oriented, and association of
humans with regular feeding often results
in sheep soliciting people for food.
Those who are moving sheep may exploit this
behavior by leading sheep with buckets of
feed.
=== Dominance hierarchy ===
Sheep establish a dominance hierarchy through
fighting, threats and competitiveness.
Dominant animals are inclined to be more aggressive
with other sheep, and usually feed first at
troughs.
Primarily among rams, horn size is a factor
in the flock hierarchy.
Rams with different size horns may be less
inclined to fight to establish the dominance
order, while rams with similarly sized horns
are more so.
Merinos have an almost linear hierarchy whereas
there is a less rigid structure in Border
Leicesters when a competitive feeding situation
arises.In sheep, position in a moving flock
is highly correlated with social dominance,
but there is no definitive study to show consistent
voluntary leadership by an individual sheep.
=== Intelligence and learning ability ===
Sheep are frequently thought of as unintelligent
animals.
Their flocking behavior and quickness to flee
and panic can make shepherding a difficult
endeavor for the uninitiated.
Despite these perceptions, a University of
Illinois monograph on sheep reported their
intelligence to be just below that of pigs,
and on par with that of cattle.
Sheep can recognize individual human and ovine
faces, and remember them for years.
In addition to long-term facial recognition
of individuals, sheep can also differentiate
emotional states through facial characteristics.
If worked with patiently, sheep may learn
their names and many sheep are trained to
be led by halter for showing and other purposes.
Sheep have also responded well to clicker
training.
Sheep have been used as pack animals; Tibetan
nomads distribute baggage equally throughout
a flock as it is herded between living sites.It
has been reported that some sheep have apparently
shown problem-solving abilities; a flock in
West Yorkshire, England allegedly found a
way to get over cattle grids by rolling on
their backs, although documentation of this
has relied on anecdotal accounts.
=== Vocalisations ===
Sounds made by domestic sheep include bleats,
grunts, rumbles and snorts.
Bleating ("baaing") is used mostly for contact
communication, especially between dam and
lambs, but also at times between other flock
members.
The bleats of individual sheep are distinctive,
enabling the ewe and her lambs to recognize
each other's vocalizations.
Vocal communication between lambs and their
dam declines to a very low level within several
weeks after parturition.
A variety of bleats may be heard, depending
on sheep age and circumstances.
Apart from contact communication, bleating
may signal distress, frustration or impatience;
however, sheep are usually silent when in
pain.
Isolation commonly prompts bleating by sheep.
Pregnant ewes may grunt when in labor.
Rumbling sounds are made by the ram during
courting; somewhat similar rumbling sounds
may be made by the ewe, especially when with
her neonate lambs.
A snort (explosive exhalation through the
nostrils) may signal aggression or a warning,
and is often elicited from startled sheep.
=== Senses ===
In sheep breeds lacking facial wool, the visual
field is wide.
In 10 sheep (Cambridge, Lleyn and Welsh Mountain
breeds, which lack facial wool), the visual
field ranged from 298° to 325°, averaging
313.1°, with binocular overlap ranging from
44.5° to 74°, averaging 61.7°.
In some breeds, unshorn facial wool can limit
the visual field; in some individuals, this
may be enough to cause "wool blindness".
In 60 Merinos, visual fields ranged from 219.1°
to 303.0°, averaging 269.9°, and the binocular
field ranged from 8.9° to 77.7°, averaging
47.5°; 36% of the measurements were limited
by wool, although photographs of the experiments
indicate that only limited facial wool regrowth
had occurred since shearing.
In addition to facial wool (in some breeds),
visual field limitations can include ears
and (in some breeds) horns, so the visual
field can be extended by tilting the head.
Sheep eyes exhibit very low hyperopia and
little astigmatism.
Such visual characteristics are likely to
produce a well-focused retinal image of objects
in both the middle and long distance.
Because sheep eyes have no accommodation,
one might expect the image of very near objects
to be blurred, but a rather clear near image
could be provided by the tapetum and large
retinal image of the sheep's eye, and adequate
close vision may occur at muzzle length.
Good depth perception, inferred from the sheep's
sure-footedness, was confirmed in "visual
cliff" experiments; behavioral responses indicating
depth perception are seen in lambs at one
day old.
Sheep are thought to have colour vision, and
can distinguish between a variety of colours:
black, red, brown, green, yellow and white.
Sight is a vital part of sheep communication,
and when grazing, they maintain visual contact
with each other.
Each sheep lifts its head upwards to check
the position of other sheep in the flock.
This constant monitoring is probably what
keeps the sheep in a flock as they move along
grazing.
Sheep become stressed when isolated; this
stress is reduced if they are provided with
a mirror, indicating that the sight of other
sheep reduces stress.Taste is the most important
sense in sheep, establishing forage preferences,
with sweet and sour plants being preferred
and bitter plants being more commonly rejected.
Touch and sight are also important in relation
to specific plant characteristics, such as
succulence and growth form.The ram uses his
vomeronasal organ (sometimes called the Jacobson's
organ) to sense the pheromones of ewes and
detect when they are in estrus.
The ewe uses her vomeronasal organ for early
recognition of her neonate lamb.
== Reproduction ==
Sheep follow a similar reproductive strategy
to other herd animals.
A group of ewes is generally mated by a single
ram, who has either been chosen by a breeder
or (in feral populations) has established
dominance through physical contest with other
rams.
Most sheep are seasonal breeders, although
some are able to breed year-round.
Ewes generally reach sexual maturity at six
to eight months old, and rams generally at
four to six months.
However, there are exceptions.
For example, Finnsheep ewe lambs may reach
puberty as early as 3 to 4 months, and Merino
ewes sometimes reach puberty at 18 to 20 months.
Ewes have estrus cycles about every 17 days,
during which they emit a scent and indicate
readiness through physical displays towards
rams.
A minority of rams (8% on average) display
a preference for homosexuality and a small
number of the females that were accompanied
by a male fetus in utero are freemartins (female
animals that are behaviorally masculine and
lack functioning ovaries).In feral sheep,
rams may fight during the rut to determine
which individuals may mate with ewes.
Rams, especially unfamiliar ones, will also
fight outside the breeding period to establish
dominance; rams can kill one another if allowed
to mix freely.
During the rut, even usually friendly rams
may become aggressive towards humans due to
increases in their hormone levels.After mating,
sheep have a gestation period of about five
months, and normal labor takes one to three
hours.
Although some breeds regularly throw larger
litters of lambs, most produce single or twin
lambs.
During or soon after labor, ewes and lambs
may be confined to small lambing jugs, small
pens designed to aid both careful observation
of ewes and to cement the bond between them
and their lambs.
Ovine obstetrics can be problematic.
By selectively breeding ewes that produce
multiple offspring with higher birth weights
for generations, sheep producers have inadvertently
caused some domestic sheep to have difficulty
lambing; balancing ease of lambing with high
productivity is one of the dilemmas of sheep
breeding.
In the case of any such problems, those present
at lambing may assist the ewe by extracting
or repositioning lambs.
After the birth, ewes ideally break the amniotic
sac (if it is not broken during labor), and
begin licking clean the lamb.
Most lambs will begin standing within an hour
of birth.
In normal situations, lambs nurse after standing,
receiving vital colostrum milk.
Lambs that either fail to nurse or are rejected
by the ewe require help to survive, such as
bottle-feeding or fostering by another ewe.After
lambs are several weeks old, lamb marking
(ear tagging, docking, and castrating) is
carried out.
Vaccinations are usually carried out at this
point as well.
Ear tags with numbers are attached, or ear
marks are applied, for ease of later identification
of sheep.
Castration is performed on ram lambs not intended
for breeding, although some shepherds choose
to omit this for ethical, economic or practical
reasons.
However, many would disagree with regard to
timing.
Docking and castration are commonly done after
24 hours (to avoid interference with maternal
bonding and consumption of colostrum) and
are often done not later than one week after
birth, to minimize pain, stress, recovery
time and complications.
The first course of vaccinations (commonly
anti-clostridial) is commonly given at an
age of about 10 to 12 weeks; i.e. when the
concentration of maternal antibodies passively
acquired via colostrum is expected to have
fallen low enough to permit development of
active immunity.
Ewes are often revaccinated annually about
3 weeks before lambing, to provide high antibody
concentrations in colostrum during the first
several hours after lambing.
Ram lambs that will either be slaughtered
or separated from ewes before sexual maturity
are not usually castrated.
Tail docking is commonly done for welfare,
having been shown to reduce risk of flystrike.
Objections to all these procedures have been
raised by animal rights groups, but farmers
defend them by saying they solve many practical
and veterinary problems, and inflict only
temporary pain.
== Health ==
Sheep may fall victim to poisons, infectious
diseases, and physical injuries.
As a prey species, a sheep's system is adapted
to hide the obvious signs of illness, to prevent
being targeted by predators.
However, some signs of ill health are obvious,
with sick sheep eating little, vocalizing
excessively, and being generally listless.
Throughout history, much of the money and
labor of sheep husbandry has aimed to prevent
sheep ailments.
Historically, shepherds often created remedies
by experimentation on the farm.
In some developed countries, including the
United States, sheep lack the economic importance
for drug companies to perform expensive clinical
trials required to approve more than a relatively
limited number of drugs for ovine use.
However, extra-label drug use in sheep production
is permitted in many jurisdictions, subject
to certain restrictions.
In the US, for example, regulations governing
extra-label drug use in animals are found
in 21 CFR (Code of Federal Regulations) Part
530.
In the 20th and 21st centuries, a minority
of sheep owners have turned to alternative
treatments such as homeopathy, herbalism and
even traditional Chinese medicine to treat
sheep veterinary problems.
Despite some favorable anecdotal evidence,
the effectiveness of alternative veterinary
medicine has been met with skepticism in scientific
journals.
The need for traditional anti-parasite drugs
and antibiotics is widespread, and is the
main impediment to certified organic farming
with sheep.Many breeders take a variety of
preventive measures to ward off problems.
The first is to ensure all sheep are healthy
when purchased.
Many buyers avoid outlets known to be clearing
houses for animals culled from healthy flocks
as either sick or simply inferior.
This can also mean maintaining a closed flock,
and quarantining new sheep for a month.
Two fundamental preventive programs are maintaining
good nutrition and reducing stress in the
sheep.
Restraint, isolation, loud noises, novel situations,
pain, heat, extreme cold, fatigue and other
stressors can lead to secretion of cortisol,
a stress hormone, in amounts that may indicate
welfare problems.
Excessive stress can compromise the immune
system.
"Shipping fever" (pneumonic mannheimiosis,
formerly called pasteurellosis) is a disease
of particular concern, that can occur as a
result of stress, notably during transport
and (or) handling.
Pain, fear and several other stressors can
cause secretion of epinephrine (adrenaline).
Considerable epinephrine secretion in the
final days before slaughter can adversely
affect meat quality (by causing glycogenolysis,
removing the substrate for normal post-slaughter
acidification of meat) and result in meat
becoming more susceptible to colonization
by spoilage bacteria.
Because of such issues, low-stress handling
is essential in sheep management.
Avoiding poisoning is also important; common
poisons are pesticide sprays, inorganic fertilizer,
motor oil, as well as radiator coolant containing
ethylene glycol.
Common forms of preventive medication for
sheep are vaccinations and treatments for
parasites.
Both external and internal parasites are the
most prevalent malady in sheep, and are either
fatal, or reduce the productivity of flocks.
Worms are the most common internal parasites.
They are ingested during grazing, incubate
within the sheep, and are expelled through
the digestive system (beginning the cycle
again).
Oral anti-parasitic medicines, known as drenches,
are given to a flock to treat worms, sometimes
after worm eggs in the feces has been counted
to assess infestation levels.
Afterwards, sheep may be moved to a new pasture
to avoid ingesting the same parasites.
External sheep parasites include: lice (for
different parts of the body), sheep keds,
nose bots, sheep itch mites, and maggots.
Keds are blood-sucking parasites that cause
general malnutrition and decreased productivity,
but are not fatal.
Maggots are those of the bot fly and the blow-fly.
Fly maggots cause the extremely destructive
condition of flystrike.
Flies lay their eggs in wounds or wet, manure-soiled
wool; when the maggots hatch they burrow into
a sheep's flesh, eventually causing death
if untreated.
In addition to other treatments, crutching
(shearing wool from a sheep's rump) is a common
preventive method.
Some countries allow mulesing, a practice
that involves stripping away the skin on the
rump to prevent fly-strike, normally performed
when the sheep is a lamb.
Nose bots are fly larvae that inhabit a sheep's
sinuses, causing breathing difficulties and
discomfort.
Common signs are a discharge from the nasal
passage, sneezing, and frantic movement such
as head shaking.
External parasites may be controlled through
the use of backliners, sprays or immersive
sheep dips.A wide array of bacterial and viral
diseases affect sheep.
Diseases of the hoof, such as foot rot and
foot scald may occur, and are treated with
footbaths and other remedies.
These painful conditions cause lameness and
hinder feeding.
Ovine Johne's disease is a wasting disease
that affects young sheep.
Bluetongue disease is an insect-borne illness
causing fever and inflammation of the mucous
membranes.
Ovine rinderpest (or peste des petits ruminants)
is a highly contagious and often fatal viral
disease affecting sheep and goats.
Sheep may also be affected by primary or secondary
photosensitization.
A few sheep conditions are transmissible to
humans.
Orf (also known as scabby mouth, contagious
ecthyma or soremouth) is a skin disease leaving
lesions that is transmitted through skin-to-skin
contact.
Cutaneous anthrax is also called woolsorter's
disease, as the spores can be transmitted
in unwashed wool.
More seriously, the organisms that can cause
spontaneous enzootic abortion in sheep are
easily transmitted to pregnant women.
Also of concern are the prion disease scrapie
and the virus that causes foot-and-mouth disease
(FMD), as both can devastate flocks.
The latter poses a slight risk to humans.
During the 2001 FMD pandemic in the UK, hundreds
of sheep were culled and some rare British
breeds were at risk of extinction due to this.
=== Predators ===
Other than parasites and disease, predation
is a threat to sheep and the profitability
of sheep raising.
Sheep have little ability to defend themselves,
compared with other species kept as livestock.
Even if sheep survive an attack, they may
die from their injuries or simply from panic.
However, the impact of predation varies dramatically
with region.
In Africa, Australia, the Americas, and parts
of Europe and Asia predators are a serious
problem.
In the United States, for instance, over one
third of sheep deaths in 2004 were caused
by predation.
In contrast, other nations are virtually devoid
of sheep predators, particularly islands known
for extensive sheep husbandry.
Worldwide, canids—including the domestic
dog—are responsible for most sheep deaths.
Other animals that occasionally prey on sheep
include: felines, bears, birds of prey, ravens
and feral hogs.Sheep producers have used a
wide variety of measures to combat predation.
Pre-modern shepherds used their own presence,
livestock guardian dogs, and protective structures
such as barns and fencing.
Fencing (both regular and electric), penning
sheep at night and lambing indoors all continue
to be widely used.
More modern shepherds used guns, traps, and
poisons to kill predators, causing significant
decreases in predator populations.
In the wake of the environmental and conservation
movements, the use of these methods now usually
falls under the purview of specially designated
government agencies in most developed countries.The
1970s saw a resurgence in the use of livestock
guardian dogs and the development of new methods
of predator control by sheep producers, many
of them non-lethal.
Donkeys and guard llamas have been used since
the 1980s in sheep operations, using the same
basic principle as livestock guardian dogs.
Interspecific pasturing, usually with larger
livestock such as cattle or horses, may help
to deter predators, even if such species do
not actively guard sheep.
In addition to animal guardians, contemporary
sheep operations may use non-lethal predator
deterrents such as motion-activated lights
and noisy alarms.
== Economic importance ==
Sheep are an important part of the global
agricultural economy.
However, their once vital status has been
largely replaced by other livestock species,
especially the pig, chicken, and cow.
China, Australia, India, and Iran have the
largest modern flocks, and serve both local
and exportation needs for wool and mutton.
Other countries such as New Zealand have smaller
flocks but retain a large international economic
impact due to their export of sheep products.
Sheep also play a major role in many local
economies, which may be niche markets focused
on organic or sustainable agriculture and
local food customers.
Especially in developing countries, such flocks
may be a part of subsistence agriculture rather
than a system of trade.
Sheep themselves may be a medium of trade
in barter economies.
Domestic sheep provide a wide array of raw
materials.
Wool was one of the first textiles, although
in the late 20th century wool prices began
to fall dramatically as the result of the
popularity and cheap prices for synthetic
fabrics.
For many sheep owners, the cost of shearing
is greater than the possible profit from the
fleece, making subsisting on wool production
alone practically impossible without farm
subsidies.
Fleeces are used as material in making alternative
products such as wool insulation.
In the 21st century, the sale of meat is the
most profitable enterprise in the sheep industry,
even though far less sheep meat is consumed
than chicken, pork or beef.Sheepskin is likewise
used for making clothes, footwear, rugs, and
other products.
Byproducts from the slaughter of sheep are
also of value: sheep tallow can be used in
candle and soap making, sheep bone and cartilage
has been used to furnish carved items such
as dice and buttons as well as rendered glue
and gelatin.
Sheep intestine can be formed into sausage
casings, and lamb intestine has been formed
into surgical sutures, as well as strings
for musical instruments and tennis rackets.
Sheep droppings, which are high in cellulose,
have even been sterilized and mixed with traditional
pulp materials to make paper.
Of all sheep byproducts, perhaps the most
valuable is lanolin: the waterproof, fatty
substance found naturally in sheep's wool
and used as a base for innumerable cosmetics
and other products.Some farmers who keep sheep
also make a profit from live sheep.
Providing lambs for youth programs such as
4-H and competition at agricultural shows
is often a dependable avenue for the sale
of sheep.
Farmers may also choose to focus on a particular
breed of sheep in order to sell registered
purebred animals, as well as provide a ram
rental service for breeding.
A new option for deriving profit from live
sheep is the rental of flocks for grazing;
these "mowing services" are hired in order
to keep unwanted vegetation down in public
spaces and to lessen fire hazard.Despite the
falling demand and price for sheep products
in many markets, sheep have distinct economic
advantages when compared with other livestock.
They do not require expensive housing, such
as that used in the intensive farming of chickens
or pigs.
They are an efficient use of land; roughly
six sheep can be kept on the amount that would
suffice for a single cow or horse.
Sheep can also consume plants, such as noxious
weeds, that most other animals will not touch,
and produce more young at a faster rate.
Also, in contrast to most livestock species,
the cost of raising sheep is not necessarily
tied to the price of feed crops such as grain,
soybeans and corn.
Combined with the lower cost of quality sheep,
all these factors combine to equal a lower
overhead for sheep producers, thus entailing
a higher profitability potential for the small
farmer.
Sheep are especially beneficial for independent
producers, including family farms with limited
resources, as the sheep industry is one of
the few types of animal agriculture that has
not been vertically integrated by agribusiness.
== As food ==
Sheep meat and milk were one of the earliest
staple proteins consumed by human civilization
after the transition from hunting and gathering
to agriculture.
Sheep meat prepared for food is known as either
mutton or lamb.
"Mutton" is derived from the Old French moton,
which was the word for sheep used by the Anglo-Norman
rulers of much of the British Isles in the
Middle Ages.
This became the name for sheep meat in English,
while the Old English word sceap was kept
for the live animal.
Throughout modern history, "mutton" has been
limited to the meat of mature sheep usually
at least two years of age; "lamb" is used
for that of immature sheep less than a year.In
the 21st century, the nations with the highest
consumption of sheep meat are the Arab States
of the Persian Gulf, New Zealand, Australia,
Greece, Uruguay, the United Kingdom and Ireland.
These countries eat 14–40 lbs (3–18 kg)
of sheep meat per capita, per annum.
Sheep meat is also popular in France, Africa
(especially the Maghreb), the Caribbean, the
rest of the Middle East, India, and parts
of China.
This often reflects a history of sheep production.
In these countries in particular, dishes comprising
alternative cuts and offal may be popular
or traditional.
Sheep testicles—called animelles or lamb
fries—are considered a delicacy in many
parts of the world.
Perhaps the most unusual dish of sheep meat
is the Scottish haggis, composed of various
sheep innards cooked along with oatmeal and
chopped onions inside its stomach.
In comparison, countries such as the U.S.
consume only a pound or less (under 0.5 kg),
with Americans eating 50 pounds (22 kg) of
pork and 65 pounds (29 kg) of beef.
In addition, such countries rarely eat mutton,
and may favor the more expensive cuts of lamb:
mostly lamb chops and leg of lamb.Though sheep's
milk may be drunk rarely in fresh form, today
it is used predominantly in cheese and yogurt
making.
Sheep have only two teats, and produce a far
smaller volume of milk than cows.
However, as sheep's milk contains far more
fat, solids, and minerals than cow's milk,
it is ideal for the cheese-making process.
It also resists contamination during cooling
better because of its much higher calcium
content.
Well-known cheeses made from sheep milk include
the Feta of Bulgaria and Greece, Roquefort
of France, Manchego from Spain, the Pecorino
Romano (the Italian word for sheep is pecore)
and Ricotta of Italy.
Yogurts, especially some forms of strained
yogurt, may also be made from sheep milk.
Many of these products are now often made
with cow's milk, especially when produced
outside their country of origin.
Sheep milk contains 4.8% lactose, which may
affect those who are intolerant.As with other
domestic animals, the meat of uncastrated
males is inferior in quality, especially as
they grow.
A "bucky" lamb is a lamb which was not castrated
early enough, or which was castrated improperly
(resulting in one testicle being retained).
These lambs are worth less at market.
== In science ==
Sheep are generally too large and reproduce
too slowly to make ideal research subjects,
and thus are not a common model organism.
They have, however, played an influential
role in some fields of science.
In particular, the Roslin Institute of Edinburgh,
Scotland used sheep for genetics research
that produced groundbreaking results.
In 1995, two ewes named Megan and Morag were
the first mammals cloned from differentiated
cells.
A year later, a Finnish Dorset sheep named
Dolly, dubbed "the world's most famous sheep"
in Scientific American, was the first mammal
to be cloned from an adult somatic cell.
Following this, Polly and Molly were the first
mammals to be simultaneously cloned and transgenic.
As of 2008, the sheep genome has not been
fully sequenced, although a detailed genetic
map has been published, and a draft version
of the complete genome produced by assembling
sheep DNA sequences using information given
by the genomes of other mammals.
In 2012, a transgenic sheep named "Peng Peng"
was cloned by Chinese scientists, who spliced
his genes with that of a roundworm (C. elegans)
in order to increase production of fats healthier
for human consumption.In the study of natural
selection, the population of Soay sheep that
remain on the island of Hirta have been used
to explore the relation of body size and coloration
to reproductive success.
Soay sheep come in several colors, and researchers
investigated why the larger, darker sheep
were in decline; this occurrence contradicted
the rule of thumb that larger members of a
population tend to be more successful reproductively.
The feral Soays on Hirta are especially useful
subjects because they are isolated.Sheep are
one of the few animals where the molecular
basis of the diversity of male sexual preferences
has been examined.
However, this research has been controversial,
and much publicity has been produced by a
study at the Oregon Health and Science University
that investigated the mechanisms that produce
homosexuality in rams.
Organizations such as PETA campaigned against
the study, accusing scientists of trying to
cure homosexuality in the sheep.
OHSU and the involved scientists vehemently
denied such accusations.Domestic sheep are
sometimes used in medical research, particularly
for researching cardiovascular physiology,
in areas such as hypertension and heart failure.
Pregnant sheep are also a useful model for
human pregnancy, and have been used to investigate
the effects on fetal development of malnutrition
and hypoxia.
In behavioral sciences, sheep have been used
in isolated cases for the study of facial
recognition, as their mental process of recognition
is qualitatively similar to humans.
== Cultural impact ==
Sheep have had a strong presence in many cultures,
especially in areas where they form the most
common type of livestock.
In the English language, to call someone a
sheep or ovine may allude that they are timid
and easily led.
In contradiction to this image, male sheep
are often used as symbols of virility and
power; the logos of the Los Angeles Rams football
team and the Dodge Ram pickup truck allude
to males of the bighorn sheep, Ovis canadensis.
Counting sheep is popularly said to be an
aid to sleep, and some ancient systems of
counting sheep persist today.
Sheep also enter in colloquial sayings and
idiom frequently with such phrases as "black
sheep".
To call an individual a black sheep implies
that they are an odd or disreputable member
of a group.
This usage derives from the recessive trait
that causes an occasional black lamb to be
born into an entirely white flock.
These black sheep were considered undesirable
by shepherds, as black wool is not as commercially
viable as white wool.
Citizens who accept overbearing governments
have been referred to by the Portmanteau neologism
of sheeple.
Somewhat differently, the adjective "sheepish"
is also used to describe embarrassment.
=== Religion and folklore ===
In antiquity, symbolism involving sheep cropped
up in religions in the ancient Near East,
the Mideast, and the Mediterranean area: Çatalhöyük,
ancient Egyptian religion, the Cana'anite
and Phoenician tradition, Judaism, Greek religion,
and others.
Religious symbolism and ritual involving sheep
began with some of the first known faiths:
Skulls of rams (along with bulls) occupied
central placement in shrines at the Çatalhöyük
settlement in 8,000 BCE.
In Ancient Egyptian religion, the ram was
the symbol of several gods: Khnum, Heryshaf
and Amun (in his incarnation as a god of fertility).
Other deities occasionally shown with ram
features include the goddess Ishtar, the Phoenician
god Baal-Hamon, and the Babylonian god Ea-Oannes.
In Madagascar, sheep were not eaten as they
were believed to be incarnations of the souls
of ancestors.There are many ancient Greek
references to sheep: that of Chrysomallos,
the golden-fleeced ram, continuing to be told
through into the modern era.
Astrologically, Aries, the ram, is the first
sign of the classical Greek zodiac, and the
sheep is the eighth of the twelve animals
associated with the 12-year cycle of in the
Chinese zodiac, related to the Chinese calendar.
In Mongolia, shagai are an ancient form of
dice made from the cuboid bones of sheep that
are often used for fortunetelling purposes.
Sheep play an important role in all the Abrahamic
faiths; Abraham, Isaac, Jacob, Moses, King
David and the Islamic prophet Muhammad were
all shepherds.
According to the Biblical story of the Binding
of Isaac, a ram is sacrificed as a substitute
for Isaac after an angel stays Abraham's hand
(in the Islamic tradition, Abraham was about
to sacrifice Ishmael).
Eid al-Adha is a major annual festival in
Islam in which sheep (or other animals) are
sacrificed in remembrance of this act.
Sheep are occasionally sacrificed to commemorate
important secular events in Islamic cultures.
Greeks and Romans sacrificed sheep regularly
in religious practice, and Judaism once sacrificed
sheep as a Korban (sacrifice), such as the
Passover lamb . Ovine symbols—such as the
ceremonial blowing of a shofar—still find
a presence in modern Judaic traditions.
Followers of Christianity are collectively
often referred to as a flock, with Christ
as the Good Shepherd, and sheep are an element
in the Christian iconography of the birth
of Jesus.
Some Christian saints are considered patrons
of shepherds, and even of sheep themselves.
Christ is also portrayed as the Sacrificial
lamb of God (Agnus Dei) and Easter celebrations
in Greece and Romania traditionally feature
a meal of Paschal lamb.
In many Christian traditions, a church leader
is called the pastor, which is derived from
the Latin word for shepherd.
Sheep are key symbols in fables and nursery
rhymes like The Wolf in Sheep's Clothing,
Little Bo Peep, Baa, Baa, Black Sheep, and
Mary Had a Little Lamb; novels such as George
Orwell's Animal Farm and Haruki Murakami's
A Wild Sheep Chase; songs such as Bach's Sheep
may safely graze (Schafe können sicher weiden)
and Pink Floyd's Sheep, and poems like William
Blake's "The Lamb".
== Gallery ==
== See also ==
Dry Sheep Equivalent
Sheepfold
Sheeple
Shrek (sheep)
Sonny Wool
U.S. Sheep Experiment Station
Venray sheep companies
== References ==
== Sources ==
Budiansky, Stephen (1999).
The Covenant of the Wild: Why animals chose
domestication.
Yale University Press.
ISBN 978-0-300-07993-7.
Ensminger, Dr. M.E.; Dr. R.O. Parker (1986).
Sheep and Goat Science, Fifth Edition.
Danville, Illinois: The Interstate Printers
and Publishers Inc.
ISBN 978-0-8134-2464-4.
Pugh, David G. (2001).
Sheep & Goat Medicine.
Elsevier Health Sciences.
ISBN 978-0-7216-9052-0.
Simmons, Paula; Carol Ekarius (2001).
Storey's Guide to Raising Sheep.
North Adams, MA: Storey Publishing LLC.
ISBN 978-1-58017-262-2.
Smith M.S., Barbara; Mark Aseltine PhD; Gerald
Kennedy DVM (1997).
Beginning Shepherd's Manual, Second Edition.
Ames, Iowa: Iowa State University Press.
ISBN 978-0-8138-2799-5.
Weaver, Sue (2005).
Sheep: small-scale sheep keeping for pleasure
and profit.
3 Burroughs Irvine, CA 92618: Hobby Farm Press,
an imprint of BowTie Press, a division of
BowTie Inc.
ISBN 978-1-931993-49-4.
Wooster, Chuck (2005).
Living with Sheep: Everything You Need to
Know to Raise Your Own Flock.
Geoff Hansen (Photography).
Guilford, Connecticut: The Lyons Press.
ISBN 978-1-59228-531-0.
== External links ==
American Sheep Industry
Sheep Industry (Queensland)
Canadian Sheep Federation
National Sheep Association (UK)
New Zealand Sheepbreeders Association
Sheep magazine, all articles available free
online
View the sheep genome in Ensembl
