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Study
Guide
- Taxonomy:
Swine belong to the Order Artiodactyla. Artiodactylids are
cloven-hooved animals, with the third and fourth toes supporting the
animals weight. Other animals in Order Artiodactyla are
cattle, sheep and deer.
Porcine is an adjective used to describe pigs.
The complete taxonomic classification of the domestic pig is:
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Artiodactyla
Family Suidae
Genus Sus
Species Sus scrofa domesticus
- History of Swine:
Swine were domesticated over 3000 years ago. They have been
used in research since Erisistratus demonstrated the flow of air in
the trachea of swine in 300 BC. Miniature pigs were developed
in the United States in the 1950s to create research swine of more
manageable size.
- The Role of Swine in Research:
Swine are increasingly used in research. Humans and swine
have similar anatomy, physiology, biochemistry and pathology.
We respond to drugs in the same way. We have similar lung size
and functional capacity, analogous renal and pancreatic
physiology; we are both monogastric omnivores and our skin is
of the same thickness and porosity.
The pig's short reproductive cycle, ease of breeding, large
litter size, diverse gene pool and early maturity contribute to its
usefulness in the lab. Pig usage in research has increased
over the last several years because they are a nonrodent alternative
to the often more expensive and more ethically objectionable dogs
and primates.
Some uses of swine in research include:
- The study of vonWillebrand's disease (a coagulation disorder
of man and dobermann pinschers)
- The study of type II diabetes (swine have also be used as a
source of natural insulin)
- Development of dermal motion sickness patches (using the pig's
hairless abdominal skin, which is analogous to human skin in
texture, permeability and thickness)
- The study of the relationship between stress and hypertension
- Development and practice of microsurgery techniques on the
urethra and oviducts
- Fetal surgery (because swine and human neonates are at a
similar development stage)
- Organ transplantation research
- Source of heart valves, livers and other structures for
xenotransplantation (transplantation of animal cells and tissues
into humans)
- Study of the role of diet, exercise and treatment of
osteoporosis in older sows
- Study of atherosclerosis and the role of dietary cholesterol
- Development and practice of wound healing and plastic surgery
techniques
- Study of obesity, anorexia and peptic ulcers and the
development of the endoscope
- Swine Statistics
| Criterion |
Swine |
Minipigs |
| Life Span |
10 - 15 years |
| Adult Size |
100 - 250 kg |
40 - 100 kg |
| Temperature |
101.6 - 103.6°
F |
100.6 - 1-2.6°
F |
| Pulse |
60 - 80 bpm |
70 - 90 bpm |
| Respirations |
8 - 18 rpm |
20 - 30 rpm |
| Estrous Cycle |
21 days |
| Gestation |
113 days (3 weeks, 3
months, 3 days) |
| Weaning Age |
6 weeks |
4 weeks |
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- Breeds Used for Research:
Swine used in research can either be domestic pigs produced from
agricultural stock or miniature swine, developed specifically for
research.
Domestic swine, such as the Yorkshire, Landrace and Duroc breeds,
are large agricultural animals with adult weights of up to 700 or
more pounds. Many farm-purchased pigs are mixed breeds.
These pigs are primarily used in acute studies in which maturity or
puberty are not important.
Miniature swine (minipigs and micropigs) were developed over the
past fifty years to provide a conveniently-size pig for
experimentation. These breeds are used in chronic studies that
relate to adult metabolism and physiology. At an adult weight
of 100 to 200 pounds, these pigs have organs that are approximately
the same size as human structures. Piglets are bone with a
similar degree of maturity and have similar growth patterns to human
neonates.
Several breeds of miniature pigs are available for use in
research. The Yucatan (Mexican hairless) pig is the only
naturally occurring miniature pig. It is native to Central
America and formed the foundation of several breeds of minipigs.
The first miniature pig to be developed what the Hormel pig in
1949. The Panepinto micropig was developed by Linda Panepinto
from Yucatan minipigs in 1978. These pigs are eighteen inches
tall and weigh less than 100 pounds. The Goettingen miniature
pig was developed in Germany in 1980 from crossbreeding a Vietnamese
pot-bellied pig with a miniature pig. Vietnamese pot-bellied
pigs are not used in research due to their excitable temperament.
- The Anatomy and Physiology of Swine:
There is considerable similarity between the anatomy and
physiology of swine and the anatomy and physiology of people.
Both swine and humans are monogastric herbivores. We both
develop peptic ulcers and may become obese. We have similar
adult sizes and organ functions. We have close-rooted
incisors, premolars and molars.
There are numerous differences between us as well.
Pigs have a mobile snout with a cartilage disk at its tip.
Swine have an excellent sense of smell, and are used to hunt
truffles (mushrooms) in France. Their canines may form large
tusks, especially in males, and are open-rooted.
Pig skin, like that of humans, is relatively hairless and is
fixed (it is not possible to lift a handful of skin away from the
body like we can in rodents, dogs and other animals).
Particularly on the abdomen, the pig's skin is very similar to human
skin in thickness and permeability. (Pig skin was the original
covering for footballs.)
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Sows are placed in farrowing pens to prevent them from squashing
their piglets. Farrowing crates are pens in which the sow is
able to stand and lie down, but not move sideways. The piglets,
however, have a greater area, usually with a heat lamp in the corner
to bring the local temperature to 85 - 95°
F. The maternal instinct of the sow is very strong, and she may
become aggressive if she feels that her piglets are threatened.
A sow is a mature female pig. A young female who has not yet
had a litter of piglets is called a gilt. Boars are intact male
pigs. When piglets are weaned, they are called shoats.
Boars can be aggressive and should be handled with caution.
Porcine courtship can be very dramatic and loud. The boar
urinates, grinds his teeth and foams at the mouth. His penis is
unique because it has a corkscrew tip.
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- Swine Temperament:
Pigs are curious, social and gregarious. They need interaction
with other pigs or humans (or both) and they are intelligent and
trainable. Most pigs are gentle, although they will nibble at
your boots and try to root under them. Some swine, however,
are dangerous, and agricultural hogs should always be treated with
respect.
Swine react adversely to rough handling or poor environmental
conditions. Be calm, relaxed and patient and train pigs to
cooperate with rewards, not punishment.
Pigs that are group housed will establish a dominance hierarchy;
until this occurs, fighting will occur, although injury to the pigs
rarely results.
Pigs are very vocal and will snort and grunt almost
constantly. When they are frightened or upset, pigs squeal
very loudly--hearing protectors may be needed.
- Swine Technical Procedures:
Identification methods used for swine include ear notching and
tags, tattoos, freeze brands and temporary crayon markers. Ear
notches and tags may be damaged by friendly chewing or dominance
displays.
The medial and lateral auricular veins are most commonly used for
blood collection and intravenous injections in swine. The
anterior vena cava is frequently used by swine veterinarians and may
be used to collect a large volume of blood; cardiac puncture is
extremely difficult in pigs.
Swine are resistant to handling--and are very vocal in their
displeasure. Gentle handling and habituating the pigs to touch
is essential. Hog panels can be used to move pigs from site to
site. These are wooden or plastic sheets that can be placed in
front of pigs to direct their movement. The pigs then freely
walk from (for example) one pen to another . A hog snare is a
device that can be used to restrain pigs for procedures. It
consists of a cable loop at the end of a pole. The loop is put
into the pig's mouth behind the incisors and over the top of the
snout. This is stressful for the pig, stressful for the handler
and should only be used when necessary. A preferred method of
pig restraint in the lab is the Panepinto sling, a hammock suspended
from a metal frame. The pig is taught to accept the sling, in
which it is place on its sternum (breastbone) with its legs through
holes in the hammock. This places the pig in a natural position
and a well-trained pig can be gently manipulated for the purposes of
the experiment, including blood collection.
- Swine Husbandry:
Many swine, including those raised commercially for meat, are
specific-pathogen free animals and are kept in a barrier facility
with restricted access. Germ-free pigs are also available.
Pigs prefer a clean environment; the classic pig wallowing in the
mud is attempting to cool itself and would use clean water instead,
if it was available. Pens should be spot cleaned daily and
sanitized a minimum of twice per week (agricultural swine defecate
one to five pounds of feces and urinate two to six liters of urine
per day!!). If the pen is large enough, most pigs will
defecate in one area of their pen and sleep in a different site.
Because of their social nature, pigs should be group housed with
three to eight animals per pen. If single housing is used,
side-by-side pens that allow visual contact are best. The
floor should be nonslip. Solid flooring allows normal foot
wear and slatted floors let feces and urine drop to a waste pit
underneath. Many facilities use a combination of floor
types. Normal rooting behavior is enhanced by deep bedding,
such as straw or wood shavings.
Access by outside personnel should be restricted to avoid spread
of disease into the pig rooms. Many commercial agricultural swine
farms are barrier facilities, and this is recommended for laboratory
swine as well. Germ-free facilities will have the most
stringent access restrictions.
The temperature in most pig rooms should be 65 - 75° F,
measured at pig level. Yucatan minipigs need a temperature of
70 - 85° F
and neonates need a hot spot under a heat lamp of 85 - 95° F.
Humidity should be maintained at 40 - 70%; low humidity can
lead to cracking and peeling skin, especially in the Yucatan minipig.
It is essential to provide enrichment for pigs. Deep
bedding for rooting and visual and physical contact with other pigs
and humans is important. Toys such as bowling balls and
hanging chains are welcomed by pigs. Even brooms and caretaker
feet make good toys!
Swine are omnivores and feral swine will eat anything.
Agricultural and laboratory swine are fed commercial swine
chow. Obesity may be a problem in swine with limited ability
to move around their pen. Automatic waterers are preferred;
pigs may root under and dump water bowls! Pigs that are
deprived of water and become dehydrated may develop salt toxicity,
damaging their central nervous system. Affected pigs may
wander aimlessly, act disoriented, stagger and become comatose.
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- Swine Health and Disease:
Swine are very susceptible to a variety of disease that may lead
to upper respiratory disease or diarrhea. It is important to
maintain a barrier to protect these animals.
Atrophic rhinitis is an upper respiratory infection, often caused
by the bacteria Pasteurella multocida or Bordetella
bronchiseptica. Affected pigs cough and sneeze and may
develop dyspnea. Piglets with atrophic rhinitis have stunted
growth. Overcrowding and poor sanitation contribute to the
development of this disease. Prevention is critical;
however, if the disease develops, antibiotics can be used.
Severe diarrhea in farm animals is often called scours. Escherichia coli and Salmonella spp. are bacteria
that can cause diarrhea.
Transmissible gastroenteritis is a viral infection that can cause
vomiting, diarrhea and dehydration. Swine influenza (hog flu)
is a virus that causes respiratory disease. Pseudorabies is
caused by a Herpesvirus and produces rabies-like signs in infected
pigs. It is transmissible to all mammals except for horses and
humans.
Piglets are iron deficient at birth and are given supplemental
iron injections when they are first born. If pigs are not
exposed to sunlight or another source of ultraviolet light, they may
become deficient in vitamin D and growing piglets may develop
rickets.
The pig's relatively hairless skin allows them to contract a
variety of skin diseases, including sarcoptic mange, ringworm and
sunburn.
Malignant hyperthermia (porcine stress syndome) is a hereditary
sensitivity to some anesthetics, especially the inhalant anesthetic
halothane. It occurs most commonly in the agricultural pigs,
such as Yorkshires. This condition also occurs in
approximately one in 50,000 people anesthetized, with a mortality
rate of 65%. The signs in pigs and people are a rapid rise in
body temperature (to 108° F
in pigs), muscle rigidity, cardiac arrhythmias and tachypnea
(increased respiratory rate). Death may occur due to
myocardial damage.
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