TECHNICAL PAPER # 71
 
                     UNDERSTANDING SHEEP PRODUCTION
 
                                 By
                          Claudia S. Ingham
 
                         Technical Reviewers
                            Paul Abrahams
                       Loren and Joanna Sadler
                        Bruce I. Sanborn, Ph.D.
 
                                VITA
                    1600 Wilson Boulevard, Suite 500
                      Arlington, Virginia 22209 USA
                  Tel:   703/276-1800 * Fax:  703/243-1865
                        Internet:  pr-info@vita.org
                     
                    Understanding Sheep Production
                          ISBN:  0-86619-314-6
              [C] 1990, Volunteers in Technical Assistance
 
                       
                           PREFACE
 
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.  The
papers are intended to be used as guidelines to help people choose
technologies that are suitable to their situations.   They are not
intended to provide construction or implementation details.  People
are urged to contact VITA or a similar organization for further
information and technical assistance if they find that a particular
technology seems to meet their needs.
 
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Patrice Matthews and
Suzanne Brooks handling typesetting and layout, and Margaret Crouch
as senior editor and project manager.   VITA Volunteer Dr. R.R.
Ronkin, retired from the National Science Foundation, lent his
invaluable perspective, as a volunteer, to the compilation of
technical reviews, conversations with contributing writers,
editing, and in a variety of other ways.
 
The author of this paper, VITA Volunteer animal scientist Claudia
Ingham, specializes in the care of horses and small stock in
Oregon.  Loren Sadler is an agricultural engineer who has been a
VITA Volunteer for many years.   He is retired, and with his wife
Joanna runs a small farm in Pennsylvania.   VITA Volunteers Bruce
Sanborn, a chemical engineer, and Paul Abrahams, a soil scientist,
have a special interest in raising sheep.
 
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA offers
information and assistance aimed at helping individuals and groups
to select and implement technologies appropriate to their situations.
VITA maintains an international Inquiry Service, a specialized
documentation center, and a computerized roster of volunteer
technical consultants; manages long-term field projects; and
publishes a variety of technical manuals and papers.
 
 
                     UNDERSTANDING SHEEP PRODUCTION
 
                   by VITA Volunteer Claudia S. Ingham
 
 
1.  BACKGROUND
 
The sheep was one of the earliest animal species to be domesticated,
with evidence that they were kept and not hunted as early as
10,700 years ago in the gorge of the Greater Zab River in Northern
Iraq.  Wool has been found in the remains of 20,000-year old
villages in Switzerland (Blakely and Bade, 1986).   Sheep are in fact
well-suited for use by people because they can digest fibrous
portions of plants.  Bacteria and fungi in the gut of sheep allow
them to use feed resources that are of little or no direct value as
human food  sources.  In this way sheep can be raised on marginal
lands or make use of crop by-products while producing meat, milk,
wool, hides, and manure.
 
Many breeds of sheep, particularly those that are native to the
desert regions of the world, use water very efficiently and can go
for several days without drinking.   They can graze far from watering
holes and place less stress upon soil and vegetation near water.  In
arid regions or those experiencing desertification, raising sheep
would help alleviate erosion and health problems common to areas
where animal and human density is too high to be supported by the
local resources.
 
Drawing on the genetic resources of the world's many sheep breeds
and using cross-breeding to achieve a desired combination of traits
can bring great benefits to people.   Whether on small plots in wet
tropics or on ranges of many hectares in drier, more varied
climates, sheep can be used to alleviate food crises or provide
products for trade or barter.
 
2.  SHEEP BREEDS AND THEIR USES
 
Among the hundreds of breeds of sheep, many produce wool that can
easily be used by the people who raise them.  Moreover, wool is
easily stored and transported.   Throughout North Africa and Asia
sheep are raised for their coarse, durable wool ("carpet wool")
that is used to make carpets, tent panels, and other heavy fabrics.
This is in sharp contrast to the United States where only 7 percent
of the wool consumed is carpet wool (Ensminger and Parker, 1986).
The Awassi is a breed commonly found in the Middle East where sheep
are raised as dual- or triple-purpose animals providing milk and
meat in addition to fiber.
 
Throughout the world finer grades of wool are used in clothing.  The
breeds of sheep that grow it are very different from those that
grow coarse wool.  Fine wool breeds in the Americas trace their
ancestry to the Spanish Merino.   Sheep of this breed were first
taken to the Americas by European explorers.   The Debouillet-Merino
was developed from European breeding stock and is common in the
American West.  Many other breeds produce fine wool of high quality
while thriving in diverse environmental conditions.
 
The Karakul, originally from what is now the Southeastern Soviet
Republics and Iran, is raised for its pelt.   Young animals (lambs)
are generally slaughtered at a few weeks of age when the hide is
soft and pliable.  Many fat-tailed sheep thrive in desert regions of
Africa and Asia.  Although belonging to the same species as the
breeds mentioned previously, they have a broad base to the tail
that allows them to store more fat than other breeds.   This energy
store allows the animals to survive harsh conditions; they can go
for long periods of time without replenishing their body water.
 
Breeds commonly used in meat production are cross-bred to take
advantage of a variety of genetic traits.   The Suffolk is popular in
the United States because it is a tall, large-framed breed.  Its
size provides the kind of lean carcass desired by consumers.  This
would not be the ideal meat breed in a country where the fat
content of the carcass is of great value.   Even where the market
demands large, lean carcasses, Suffolks are cross-bred for other
traits.  They are not known for their mothering ability and so may
be cross-bred to ensure that lamb survival rates are as high as
possible.  Range flocks often use a cross-bred Dorset ram (adult
male) because they have sturdier legs and will be able to breed
more ewes (females) in a lifetime.
 
The Hampshire is another popular meat breed in the United States
that also yields a coarse to medium wool.   Its dual purpose and
adaptability to wet climates are assets where such traits are
desirable.  It is generally raised in farm flocks and not on range.
 
The Finnsheep has found popularity in some breeding programs,
including those in Third-World countries.   Though not a very hardy
sheep due to its extremely fine bones it is prolific; ewes have 3-4
lambs at a time and are good mothers.   These positive reproductive
characteristics have made it popular in cross-breeding projects.
Such positive traits must be considered with regard to the production
system and resources available.   If these sheep were to be
raised in an area where inadequate feed was available for lactating
ewes, then the death loss due to inadequate milk supply would not
warrant the investment in the Finn ewes.
 
Throughout the Third World there are many breeds of sheep appropriate
to the needs of family or commercial producers.   It is estimated
that there are 300 million sheep in Third-World countries (Smith,
1985); this is 30 percent of the world's sheep population.  Drawing
on this vast resource it is possible to choose breeds best suited
to the environmental conditions of an area as well as the product
needs of the people raising the animals.   Cross-breeding is one of
the most effective tools we have for improving or altering sheep
products.  Its application must take into account many variables
including available resources and any diseases endemic (naturally
occurring) to an area.  The prudent use of cross-breeding can allow
the shepherd to combine the traits most desirable to a specific
production system.
 
3.  RESOURCES FOR SHEEP PRODUCTION
 
Fencing of Pasture and Range
 
The area intended for raising sheep should be evaluated before the
first animal is purchased.  One might decide to buy one pregnant
ewe, in which case a small pen would be sufficient if feed is to be
brought to the animal.  A flock requires a large pasture or range.
 
If the sheep are to be confined, not herded by a shepherd, fencing
must be adequate to keep the animals within an area.   Less labor is
required for daily herding with a fenced range or pasture.   The one-time
costs of materials and labor to construct the fencing are
significant.  The costs of repairs and availability of fencing
material in the future (over many years) should also be considered.
 
Fences can be built from a variety of materials.   Wherever possible,
local material should be used as this will make the fence more
affordable and any fence repair can be done easily because supplies
are readily available.  Wood panel fencing is ideal for sheep
although it is usually the most costly type of fencing.   Barbed wire
and rolled wire are commonly used.   In a pasture where lambs will be
kept, the strands or boards will need to be close together so that
the lambs do not escape.  Mesh fencing is commonly used for young
lamb pasture.  The mesh should be small enough that the lambs do not
push their heads through and get stuck.   A mesh of 15 cm is generally
better than a larger size mesh (Ensminger and Parker, 1986).
 
The lowest strand or board in the fence should be no more than 10
cm from the ground, to ensure that sheep neither push the wire up
and escape, nor--worse--become entangled and injured.   A fence 120
cm in height is usually tall enough to maintain a flock.  The height
depends on the breed to be raised.   Large aggressive rams may need
to be kept behind a more sturdy fence, perhaps of wooden plank.
 
Securely planted posts and well-built gates are essential to good
fencing.  The width of openings will depend on how many animals are
to be herded through them and what, if any, machinery will need to
pass through gates.
 
Fencing is not always necessary for sheep production.   In the
Western United States many flocks are maintained on open range and
are never confined until put in pens at a finishing feedlot or
packing house.  Nomadic peoples herd sheep throughout Northern
Africa and Asia without fencing.   Sheep herded this way have a
strong flocking instinct, which makes a migratory existence practical
for the herder.  Their tendency to stay near other sheep,
particularly when confronted by danger or at night, increases the
survival rate of animals where predators or harsh climate are daily
challenges.
 
Nomadic shepherding requires knowledgeable herders and great
adaptability on the part of the sheep and their keepers.  Although
44 percent of the world's sheep are kept in this fashion (Smith,
1985) it is not likely that a new sheep program would include such
an extensive production system.   A possible exception would be where
groups of nomads already herding camels, cattle, or goats wish to
add sheep to their herds.  This might be done where cattle are
inappropriate due to drought conditions or where a new market
exists for the sheep or their wool or milk.
 
Quality of the Feed Resource
 
The quality of forage and seasonality of plant growth should be
determined when selecting the pasture or range on which the sheep
will be kept.  The species of plants, rainfall variation, and soil
type will all affect the nutritional composition of the pasture.
Although one species may reach its peak in protein content in the
spring, others may be just starting to grow then.   Most vegetation
is of highest digestibility just prior to flowering or the beginning
of reproduction.  All these factors must be considered in order
to maximize production from a pasture resource.
 
Although chemical analysis is the most accurate way to assess
nutrient composition of plants, experienced animal scientists and
herders can make assessments by inspection.   Accurate assessments
require familiarity with the grasses, legumes, or brush.  A grass
that is green and lush-looking may nevertheless not be digestible
by sheep for a variety of reasons.   Some plants produce toxins and
are not palatable to sheep.  In some cases the water content may be
so high that little nutritional value is realized.
 
Determining how many sheep can be fed on a given amount of pasture
also depends on the breed of sheep and the reproductive cycle of
the flock.  In areas where plant growth is constant throughout the
year and where day length varies little, sheep mate throughout the
year as well.  It is up to the manager to decide when lambs should
be born to best match the resources available.   Where there is a
market incentive to produce lambs "off season" the cost of supplemental
feed may be warranted.  In some locales supplemental feeding
will always be necessary.  This may include vitamins and minerals or
energy and protein supplements depending upon the flock's requirements.
 
Knowing the quality of the feed resource, the herd's requirements
and the timing of availability will go a long way toward meeting
the goals of the producer.  The willingness of the sheep to eat
particular feeds is not always predictable.   Although not known to
be fussy eaters, sheep do have preferences.   They will eat weeds and
brush but they prefer grasses and legumes.   Such factors need to be
included, whenever possible, when assessing the carrying capacity
of the land and the impact of the sheep on vegetation.
 
Life-Cycle Nutritional Requirements
 
Ewes and rams require the least energy, protein, vitamins, and
minerals per unit of body weight.   For the ewes, these requirements,
amounting to 2.5 to 3 kg equivalent in dry forage per day for each
animal, increase during breeding and during pregnancy and lactation.
Young lambs have high nutritional requirements, particularly
of protein, for growth.
 
Most managers recommend that the nutritional level of ewes be
increased just before breeding.   This can be done in several ways.
Ewes may be placed on superior pasture two to three weeks before
introducing rams to the herd.   In many places ewes are grazed on
crop stubble so that they may make use of the residue.   Where
available, grain can be fed to condition the ewes.   The last method
is the least desirable.  First, it is likely the most costly alternative;
second, it is difficult to gauge how much grain each ewe
will consume and ewes are likely to become too fat.   The aim of
flushing, as the period of conditioning is known, is to increase
the ovulation rate of the ewes.   Although the mechanisms are not
fully understood, this is a generally accepted practice.  In order
for flushing to be successful it must be done 10 to 20 days prior
to introducing rams.  If it is begun any sooner the advantage of
increased ovulation rate is not realized.   Excessively fat ewes
produce fewer lambs, in fact.   Rams should also be conditioned, by
feeding an energy and protein supplement approximately one month
prior to breeding.
 
Gestation in sheep takes 144 to 155 days.   During the first two-thirds
of this period, the requirements of ewes do not increase
significantly.  They must have adequate feed and water but this
requirement is only slightly above that of maintenance.   During the
last third of the period of gestation, when most of the growth
occurs in the fetuses, the ewes require 1 1/2 times the feed of
maintenance.  It is important that grain or a crop by-product be fed
at this time if the pasture resource is not adequate.   The number of
lambs the ewe is carrying and climatic stress will also effect the
nutritional needs of the ewe.
 
Lambs require little care, but up to 20 percent of newborn lambs
may die if no attention at all is given.   Disinfect the umbilical
cords of newborns in iodine solution to prevent infection.  One good
method of preventing losses of new lambs is to put the mother and
the lambs in a small pen (1.5 m square) for two days after birth,
and frequently verify that the lambs are nursing.   If they are noisy
and have cold mouths they are not nursing and will die.   The teats
of the mother may need to be checked to make sure they are not
clogged and the lamb may need to have its mouth placed upon the
teat until it learns to suck.   The manager should ensure that all of
a ewe's teats are being used.   If lambs nurse and, starting at two
months, are kept free of worms, they will likely survive.
 
Lambs raised for meat may be fed 1 kg of grain (maize) daily for
the last two months, then slaughtered at about 50 kg live weight.
 
Detailed tables of the nutrient requirements of sheep for maintenance,
early and late pregnancy, and lactation in ewes as well as
for early and late weaned lambs and finishing (being fattened for
slaughter) lambs are available from the National Research Council
in Washington, D.C. Although these figures have been determined
through extensive research, they should not be applied blindly to
any situation.  The sheep involved in these trials were in superb
health, free of parasites, and maintained in a thermoneutral
environment.  A thermoneutral environment is one in which the animal
neither gains nor loses heat from or to its surroundings.
 
Sheep raised in the tropics or sub-tropics will undoubtedly have a
greater heat load than those in temperate zones; this difference
will influence their feed intake and thus the extent to which the
needs for growth, reproduction, or other body functions are met.
Climatic stress and health status will also influence the animal's
ability to eat and to utilize its feed.   This cannot be exactly
determined in terms of grams of feed, but should be considered when
determining feed requirements and desired levels of production from
the flock.
 
 
Terrain
 
Physical features of pasture or range can be as important as the
plants and fencing.  Such important features include rocks, slope of
hillsides, drainage, and elevation.
 
Sheep can harvest feed in areas of somewhat rough terrain where
most animals cannot be successfully raised.   Pasture that is
extremely hilly or has many large rocks will reduce the animals'
ability to graze.  The sheep will tend to bunch up in the flatter,
less rocky areas and may overgraze these more accessible areas. The
animals' feet may become bruised from the rough terrain, making it
more difficult to move around and graze.   Lame animals are usually
the thinnest and least productive individuals in a herd.  Another
serious problem is the accumulation of feces and urine.   Excessively
wet soil encourages foot rot (caused by a soil bacterium and a
fungus) and survival of parasites.
 
Extreme slopes can obscure sunlight, thus retarding plant growth.
Shade plants may thrive in such an area and in such a situation it
would be worthwhile to determine if sheep will eat these plants
before planning the number of sheep to be kept there.   Supplemental
feeding is an option where forage or crop by-products are available
and affordable.  The cost of bringing the feed to the animals must
be included in planning.
 
Ensminger and Parker (1986) state that for every 305 meters gain in
elevation, vegetative development is delayed 10-15 days.  Although
this figure refers to rangeland in the Western United States, there
is also an elevation effect at or near the equator.   High elevations,
such as Mt. Kenya and Kilimanjaro in Africa and Kotopaxi in
South America, are examples.   Vegetation in the foothills and slopes
of these peaks is surely influenced by altitude.
 
Variation in growing season due to altitude and the type of terrain
are important in determining the feed resource available for sheep
production.  By taking these factors into account--as well as the
biological factors of the plants--one can determine the number of
animals that can be kept per hectare, known as the stocking
capacity.
 
Herding and Handling the Flock
 
Sheep that have been on range are most likely to gather into a
group when approached by people.   If frightened or chased by a
predator they will become scattered and more difficult to herd into
a corral.  In many countries, dogs are often used to assist in
herding of sheep.  These are well-trained animals that know how to
move sheep  slowly and at the command of the shepherd.  Untrained
dogs should never be around sheep because they will chase them like
prey.  Dogs are natural hunters and therefore enemies of sheep, so
great care must be taken if one plans to use sheep dogs for
herding.
 
Farm flocks of sheep may not be as accustomed to being herded.  The
more sheep are herded and handled, the calmer they will be and less
likely to be injured.  As with sheep on range, they should be
approached slowly and moved into a small corral for handling.
 
A herd should be put into a corral for routine care, such as foot
baths, vaccinations, or shearing, or prior to transport for sale.
Frightened sheep will run at fences and may try to jump out of
corrals.  Panic will result in injuries and makes the animals more
difficult to handle in the future.
 
Some herders recognize individuals by horns, wool on the face,
size, or coloring.  Ear tags or paint brands on the wool can also be
used.  Ear tags are the most reliable method if properly punched in
the animal's ear.  Paint washes out of the wool or brands become
distorted as the wool grows.   Where wool is a marketable product,
paint brands should easily wash out so as not to reduce the value
of the wool.
 
Chutes are useful to confine individuals.   They should be wide
enough for one sheep at a time to walk through but not turn around
and walk out the way it entered.   When the chute is full of sheep
they will not be able to move because they are held in place by the
animals in front of and behind them.   This is an ideal time to check
the health of individuals.
 
Routine Health Checks
 
One should have a system for examining an animal before moving on
to the next one.  Keeping records of individual health is very
useful in assessing performance.   Persistent problems will be
identified if records are kept from month to month.
 
The eyes and ears of the sheep should be examined.   Runny eyes may
indicate infection.  Some species of flies will lay their eggs in
the eyes; hatched larvae then cause swelling, hemorrhage, and
possibly blindness.  Eyes should be cleaned and ointments applied if
necessary.  Most sheep have some nasal discharge but thick or
discolored discharge may indicate disease.   Irregular breathing
accompanied by nasal discharge or coughing are signs of pneumonia.
 
It is good practice to examine the sheep's hooves.   This requires
turning the animal on its back outside the chute.   Grasp the sheep's
jaw firmly in one hand.  (Never hold the sheep by its wool as this
will cause bruising.)  Turning the animal's head to face its rump
and push its hindquarters to the side, then flip the sheep onto its
tail.  The animal is relatively immobile in this position, with its
weight on its lower vertebrae.   At this time trim the hooves and
check for foot rot.
 
While a ewe is on her back, check the teats for injuries or infection.
Likewise examine rams' testicles for any abnormalities.   Treat
any wounds with antiseptic ointment.   For more serious infections
antibiotic injections may be necessary.   Individuals requiring
special care should be separated from the main flock as they leave
the chute or holding pen.  They are then kept in a small pasture so
they can be more easily treated.
 
Finally, examine the dock (area around the anus and vagina).
Diarrhea is common is recently weaned lambs that are adjusting to
a new diet.  Diarrhea in older animals may be an indicator of poor
nutrition or internal parasites.   Where feces have accumulated in
the wool around the dock, flies are likely to lay their eggs and
cause damage to the animal.  In wet climates or where flies are a
problem the wool is often cut away from the dock to prevent
infection.
 
Other Health Considerations
 
Although sheep diseases are numerous, losses from disease are
usually moderate to low.  Maintaining the health of a herd or a
single animal involves the same basic principles.   A visual
assessment of individuals, as described in the previous section,
will allow the animal manager to find problems and take action
before the animal's health and productivity suffer.
 
A thorough survey of even the major diseases is beyond the scope of
this short paper.  Some health problems require a veterinarian for
diagnosis and treatment.  Veterinary services are very costly,
especially related to the economic return from a single sheep.  For
this reason and because such services are not always readily
available, it is worthwhile for the manager to be acquainted with
common diseases and know how to prevent them or give simple
treatment.  Common or noteworthy diseases are listed below:
 
Anthrax is a very serious disease because the bacteria that cause
it multiply very rapidly in the body and death usually occurs in a
few hours.  The disease is highly contagious and is deadly to humans
also.  It is passed in contaminated water and animal products, such
as wool (hence the term "wool sorter's disease") and hides.  The
disease is widespread in the tropics, where the bacteria have many
reservoirs and multiply rapidly.   In these areas vaccination is
recommended (Robertson, 1976).
 
Brucellosis is a bacterial infection that causes abortion.  It is
highly contagious from animal to animal and to humans.   It is passed
in milk and other body fluids.   Animal handlers may be infected by
airborne transmission of infectious agents at lambing (birth of
lambs).  Some countries have brucellosis policies that require the
slaughter of all infected animals because of the seriousness of the
disease in humans.
 
Enterotoxemia, or overeating disease, is common where sheep are fed
grains.  Signs include sudden loss of appetite, staggering, convulsions,
and death.  Treatment consists of using antitoxins under
specialist supervision.  Vaccines are available to prevent the
disease.
 
Foot-and-mouth is a viral disease spread by direct contact between
infected animals, which contaminate their surroundings and spread
the disease.  Mouth lesions, mastitis, muscle degeneration, and
eventually foot lesions are symptoms.   Vaccinations are available
but offer immunity for only four to six months.   Where control
measures are enforced, animals are quarantined and infected animals
slaughtered if a disease-free zone is to be established.  This
disease has been studied extensively in cattle because they are
most often infected and are transported between countries in larger
numbers than sheep.
 
Foot rot is a common problem that can be prevented by proper
management.  Sheep kept on wet pasture or dirty bedding develop
foul-smelling decay between the wall and sole of the hoof.  Well-drained
soil and clean bedding will help prevent this disease.
Vaccinations are available but are costly and may not be available
throughout the world.
 
Lamb dysentery or scours is seen in the lamb as a loose stool and
fever during the first few days after birth.   Having too many sheep
in a small area favors the bacteria that cause the disease.  Death
can come quickly.  Prevention involves good sanitation and keeping
the living quarters dry.  Treatment with antibiotics is only
partially effective.
 
Ewes with mastitis (infected, swollen udder) may have injured
mammaries or may have been suckled by a lamb that spread the
disease.  Good sanitation and isolation will prevent spread.  If a
ewe has a persistent problem she should be culled (removed from the
flock and sold or slaughtered).
 
Pneumonia is a lung disease of sheep throughout the world.  It is
caused by any of several different bacteria.   Animals living in damp
conditions, particularly where ventilation is inadequate, are most
susceptible.  Proper sanitation and ventilation will help prevent
it.  Some pneumonias clear up as the weather changes; some will
cause the animal to stop eating and may cause death.   The disease
can be treated with antibiotics.
 
Pregnancy disease occurs in ewes during the last two weeks of
pregnancy.  The ewe trembles when exercised, shows weakness, and may
collapse.  If the ewe aborts her lamb(s) the symptoms will disappear
unless the disease has been neglected too long.   Prevention consists
of an adequate diet of grain during the last few weeks of pregnancy.
Treatment consists of feeding high-energy foods such as
molasses.
 
Sheep pox or sore mouth is a viral disease commonly seen in lambs.
It causes lesions and then scabbing around the mouth and on the
teats of ewes.  Humans are infected when handling infected animals.
The disease usually runs its course with no long-term ill effect
unless lambs are unable to suckle for a long period and become
emaciated.  Live vaccines are available for use if the problem is
serious in a flock.  Generally vaccine use is not warranted.
 
Sore mouth is often confused with blue tongue, which also causes
lesions but is not transmitted directly from sheep to sheep.  Infected
animals will not eat, have swollen tongues, become stiff, and
develop secondary infections, commonly pneumonia.  Muscle tissue is
also affected.  Animals should be vaccinated once per year and kept
on well-drained ground to avoid transmission by blood-sucking
insects (Robertson,1976).
 
Tetanus is a bacterial disease that attacks the central nervous
system of all infected animals causing paralysis and death.  It
enters the body through wounds and is commonly found in the soil.
Vaccination, good management and sanitation are the best preventive
measures.
 
Tetanus and other diseases, including black quarter, big head in
rams, and pulpy kidney disease, are caused by bacteria that belong
to the Clostridium genus.  Clostridia are found in soil and feces
and so exposure to these diseases is common.   The infection often
enters through a wound or, in the case of pulpy kidney disease, the
bacteria are ingested.  By keeping the animals' housing clean and
preventing injuries by not crowding, these diseases can be prevented.
Sudden changes in diet will precipitate some clostridial
infections and so any change should be made gradually.   If the sheep
are to be put on rich pasture where their intake cannot be controlled,
they should be allowed on it for only a few hours each day
until their digestive systems adjust to the dietary change.
 
Sheep owners should be aware of the diseases that are common in
their own areas.  Such internal parasites as liver flukes, lungworms,
and intestinal worms are problems throughout the world.
Where animals are in a continuously wet climate they are likely to
be infected throughout the year and in some cases develop an
immunity to certain parasites.   In seasonally wet climates the
parasite burden is worst after the onset of rains, when the animals
become infected.  Although a program of regular de-worming can
sometimes be replaced by frequent rotation of pasture land, the
threat of stomach worms usually requires that a sound de-worming
program be in place when sheep raising is started.   If a program is
established it should be maintained because the animals will lose
any immunity to infection if not exposed to the parasite.  Good
management can prevent many kinds of infection so a combination of
preventive and control measures should be used.
 
Infection with such external parasites as ticks, fleas, maggots,
mites, and lice should be treated as recommended for the geographic
area by a veterinarian or animal-care specialist.
 
Some diseases, many of which are not mentioned here, are controlled
by laws that require owners to vaccinate or otherwise treat their
livestock.  This is particularly true where animals are to be transported
between regions of a country or across international
boundaries.  Certificates proving vaccination, or negative blood-test
results for various diseases, are included in the law
enforcement procedure.
 
Veterinarians or regional livestock officers of an extension
service are good sources of information on local disease problems
and recommended management techniques.   The Handbook on Animal
Diseases in the Tropics provides good reference material.  It outlines
transmission, symptoms, prevention, control, and treatment.
 
4.  SCALE OF THE OPERATION
 
The scale of the production system will always place certain
restrictions on what can be achieved from raising sheep.  If one
raises a large number of sheep the cost of labor, feed, veterinary
care, and marketing will be high.   Whether or not the cost will be
higher per unit of product, as compared with a family flock of just
a couple of sheep, depends on the quality of management and factors
of the marketplace.  A wise choice of resources and attention to the
details of daily management are keys to success no matter how large
or small the endeavor.
 
A family may choose to raise one or two sheep.   Many village
cooperative projects have been established that allow individuals
to lease a ram for a few weeks to breed ewes.   In this way the cost
of buying and then maintaining the ram is not the burden of one
family.  Cooperative marketing is also helpful where wool is collected
from several families and sold at once to a processor.
 
In any size operation lambs may be slaughtered for meat, and milk
may be used for family consumption.   Timing of breeding can allow
for a year-round supply of these products.   Care must be taken not
to deprive lambs of necessary nutrients if milk is to be used for
human consumption.
 
Large commercial sheep operations are based on an assumed market.
It would not be profitable to raise lambs or regularly shear wool
if there were not a way of transporting and selling those products.
The costs of shipping live animals to a slaughter house and the
effect of this transport on the sheep should be considered.  If meat
or milk is to be shipped, refrigeration or other preservation
methods must be readily available.   Coordinating the production time
and the demands of the market, whether it be in a regional or
international market, is a complicated, but quite possible, task.
 
Marketing meat and wool is an especially challenging endeavor
because there are many countries that already have a large share of
the market.  New Zealand and Australia are two such countries.  A
wise approach might be to introduce a slightly different product
than is currently available to importing nations.   In this way one
can take advantage of a new niche in the market.   A thorough knowledge
of import restrictions is mandatory because many nations have
experienced serious disease problems from imported animal products.
 
Despite the complexity and cost of producing sheep it is possible
to benefit from their products.   A thorough knowledge of the sheep's
requirements for growth and disease prevention will aid every
manager in realizing the potential from these versatile animals.
Indeed, with any livestock program that is new in the area, a
highly experienced person should plan to be in residence for an
extended period.  Applying basic concepts to specific climatic and
cultural conditions requires adaptability and foresight on the part
of the animal manager.
 
                           REFERENCES
 
The following addresses are in the United States unless otherwise
shown.
 
Blakely, J., and Bade, David H.   The Science of Animal Husbandry,
4th ed. New York:  Prentice-Hall, 1986.
 
Cole, H.H., and Garrett, W.N. (eds.).   Animal Agriculture:   The
Biology, Husbandry and Use of Domestic Animals. San Francisco:
W.H. Freeman and Co., 1980.
 
Ensminger, M.E., and Parker, R.O. (eds.).   Sheep & Goat Science.
Danville, Illinois:  Interstate Printers and Publishers, 1986.
 
National Research Council.  Nutrient Requirements of Sheep.
Washington, D.C.:  National Academy Press, 1985.
 
Robertson, A.R. (ed.) Handbook on Animal Diseases in the Tropics.
Abingdon, U.K.:  Burgess & Son, 1976.
 
Smith, A.J. (ed.) Beef Cattle Production in Developing Countries.
Avonmouth, U.K.:  Western Printing Services, 1976.
 
Smith, A.J. (ed.) Milk Production in Developing Countries.
Trowbridge, U.K.:  Redwood Burn, Ltd., 1985.
 
Webster, C.C. and Wilson, P.N. Agriculture in the Tropics. New
York:  Longmans, 1980.
 
========================================