Welcome to the course Working With Swine in Research Settings.

This is the swine module in a course series on the preparation of an animal use protocol. Swine represent one of the earliest recorded research models, having been used by Erasistratus in second century B.C. Greece to study the mechanics of breathing, and by Galen in second century A.D. Rome to demonstrate blood circulation. Today pigs are popular models for surgical research and teaching, cardiovascular studies and xenotransplantation work (transplant of tissues for which the donor is of a different species than the recipient - e.g. pig to man). The plate above shows Galen using a pig to teach students.

Each course in this series refers to a different animal species. Every course offers information that is both pertinent to all research animals and specific to the one animal species presented.

• The first 7 lessons are similar in all courses of this series. Differences in these lessons relate mainly to the regulatory coverage, housing requirements, and the zoonotic hazards of each animal species.

• The remaining lessons present information that is more specific to each animal species, such as biological features, anesthetic doses, and biomethodologies.

The goal of this course is to cover important information about using swine in biomedical research settings. If you are responsible for handling swine or if you must write an animal use protocol, this course will be useful by providing you with:

• Information on key regulatory issues.
• Guidance on searches for alternatives in the care and use of animals.
• Highlights of unique biological features of these animals.
• Overviews of acceptable basic methodologies.
• Requirements for supportive care procedures.

Hypertext links in this course provide you with supporting information, such as regulatory sources, drug doses, practical tips, etc.

This course will not provide you with detailed information on how to conduct the methods and procedures described. For this, you should use other courses offering in-depth information and hands-on instruction from your institution's animal facility staff.

Click here to view the credits for this course.

To ensure the humane treatment of laboratory animals, biomedical research and teaching involving swine is regulated by two federal agencies:

• The United States Department of Agriculture (USDA) / Animal Care; and
• The Public Health Service (PHS) / Office of Laboratory Animal Welfare.

However, swine used for research related to production of food or fiber are exempted by law from regulations promulgated under the Animal Welfare Act and administered by the USDA. Sometimes this creates some confusion among investigators and Institutional Animal Care and Use Committees (IACUCs).

If your institution receives any funding from the PHS or is voluntarily accreditated by the Association for Assessment and Accreditation of Laboratory Animal Care, International (AAALAC), then your research must also comply with the National Research Council publication, the Guide for the Care and Use of Laboratory Animals. This document will simply be referred to as the Guide in this course. Depending on the kind of research being conducted, standards described in the so-called "Ag Guide", the Guide for Care and Use of Animals in Agricultural Research and Teaching may be used in place of those in the NRC Guide.

The Public Health Service Policy requires institutions to have an occupational health and safety program for individuals working with laboratory animals. This requirement is also reiterated in the Guide.

It is the responsibility of principal investigators to assure that their laboratory staff are informed of and participate in their institution's occupational health and safety program.

Elements of an occupational health and safety program, including institutional responsibilities, are described in the guideline, Occupational Health and Safety in the Care and Use of Research Animals (shown at right), published by the National Research Council.

Working with swine is associated with the following hazards:

Allergies
People can develop an allergy to many animal species after having contact with them for some time. Allergy to pig antigens appears to be uncommon but it has been rarely reported in farm workers. Persons who develop allergy symptoms should seek medical counseling and may have to discontinue working with this species.

Injuries Swine are inquisitive and persistent animals. They tend to root at handlers working within their pens, and may cause injury by precipitating falls. While bites are not common, they are capable of biting and may try to "nibble" at handlers unless they are actively discouraged from doing so.

Swine grow to heavy weights rapidly and personnel also may be injured by lifting them - as when using the muscles of the back (instead of the legs) to pick up a pig from the floor. Except for very young animals, it is usually advisable for at least two people to be involved in lifting swine. Injuries are more likely when personnel lack the knowledge of how to handle, transport, and restrain swine.

Likewise, poor technique in handling, etc., can cause injury to the animal. Training staff to work effectively and humanely with swine is essential to prevent injuries to people and animals.

Zoonoses
In general, transmission of zoonotic disease from naturally infected laboratory animals is uncommon because of the ongoing efforts to improve the health status of animals by vendors and by facility staff.

Swine are often obtained from sources that may be less rigid in their animal health surveillance and preventive practices than is typical for laboratory rodents, so health surveillance programs within the research institution, routine sanitation, and personal protective equipment have important roles in preventing zoonoses.

Swine can be a reservoir of the following infectious agents which are transmissable to people:

Viruses

Influenzavirus type A has been reported in humans exposed to swine infected with the same serotype. The disease in people is an acute, respiratory infection characterized by fever, chills, headache, muscle aches, pharyngitis and cough. Transmission is by aerosol or direct contact with droplets. Recovery is usually complete after one week and mortality is usually low. However, mortality may be high in immunosuppressed persons, and type A influenza caused a pandemic in 1918 with high mortality. The image above shows a transmission electron micrograph of Type A Influenzavirus

Vesicular stomatitis is caused by an RNA virus in the family Rhabdoviridae. Most human infections have been acquired in the laboratory. Transmission in humans has been by aerosol or through breaks in the skin. The disease in humans is characterized by sudden onset of fever, headache, retro-orbital pain, and muscle aches. Vesicles may appear in the mouth , pharynx or on the hands and nausea, vomiting and diarrhea sometimes occur. Vesicular stomatitis is currently not endemic in the United States, but breaks in U.S. swine have occurred historically.

Erysipelothrix rhusiopathiae causes erysipelas in swine and erysipeloid in humans. The disease in humans may be localized and cause a progressive, erythematous swelling, burning pain and/or itching. When generalized it causes fever, headache, and myalgia. In the pig it produces so-called "diamond skin disease" and endocarditis. It is transmitted by direct contact with infected animals or their excreta. The photo shows the hand of an infected handler.

Brucella suis causes a systemic disease in humans that is characterized by undulating fever, chills, sweating, myalgia. There are typically spontaneous relapses and it may be complicated by arthritis or cardiac involvement.

Campylobacter jejuni, Escherichia coli, and Salmonella spp. are all causes of gastroenteric infections that may be asymptomatic or cause severe diarrhea, vomiting and occasionally sepsis. Transmission is by oral/fecal exposure.

Bacillus anthracis is the agent that causes anthrax. The organism affects domestic and wild ruminants and swine. It causes cutaneous, intestinal and pulmonary syndromes in humans with mortalities of 5-20% for untreated cutaneous disease, 50% for intestinal disease and 100% for pulmonary disease. Transmission is by direct contact with infected tissues or inhalation of spores.

Protozoa

Balantidium coli is a ciliate that may be carried asymptomatically in swine or it may be associated with diarrhea. Humans are generally resistant except when immunosuppressed when it may be associated with mucoid or bloody diarrhea, dystentery, or even hepatic abscessation and death. It is transmitted by oral/fecal exposure. The image shows a photomicrograph of a B. coli trophozoite from an infected stool sample.

For more information, on zoonoses associated with laboratory animals refer to Occupational Health and Safety in the Care and Use of Research Animals, published by the National Research Council.

Federal regulations require investigators to provide a written assurance that alternatives are not available for proposed procedures in animals that are likely to cause pain and/or distress. If alternatives are available but are not satisfactory for the proposed research, the investigator is required to explain why the proposed procedures must be used instead of the less distressful alternatives.

Your protocol form, therefore will ask you for an assurance that you have considered alternatives to the use of animals if painful or distressing procedures are proposed in order to satisfy the mandate by the Animal Welfare Act and PHS Policy to avoid or minimize discomfort, pain, and distress consistent with sound scientific practices.

Alternative procedures are those which may replace animals with nonanimal methods, reduce the number of animals used, or refine the methodology to minimize animal pain or distress.

For more information on what is meant by alternatives to the use of animals, please refer to the course Working with the IACUC, which is part of this series.

The assurance must take the form of a written narrative that describes which sources were used to determine that alternatives were not available.

Although other methods may be acceptable (for instance, expert knowledge in a very specialized field) the USDA considers a computer database search to provide the best information, and typically, you may be asked to provide the results of a database search.

If a database search is used, the following elements of the search must be described:

1. The databases that were searched.
2. The date the search was performed.
3. The years of citations covered by database searches.
4. The key words and/or search strategy used when searching a database.

The IACUC is responsible for determining whether or not a thorough search for reasonable alternatives was conducted and the USDA looks at the above elements when it reviews the IACUC's performance. It is strongly recommended that this information be sought during development of a protocol.

Organizations that can assist you in performing an alternatives search are:

• ALTWEB, Center for Alternatives to Animal Testing, Johns Hopkins University
• Animal Welfare Information Center, National Agricultural Library
• Center for Animal Alternatives, University of California – Davis

The following is a case study of alternatives searches that may guide you in the development of a search strategy that is pertinent to your own research.

Click on a link below for a sample search on key terms for this example.

The links will take you to the named database where you can conduct a search in real time.

Example Search:
Study of intravascular stents in swine.

PubMed

BIOSIS

More Example Searches:
Additional search routines are available elsewhere in this course to provide you with guidance on performing searches on alternatives in the care and use of animals related to the lesson topic.

All of the federal laws, regulations, policies and guidelines applicable to animal research have as their core intent the humane treatment of the animals involved in a study. Accordingly, your IACUC will have requirements for the proper care of your animals prior to, during, and after a research procedure.

What is a procedure? A procedure is any activity carried out on the animal, including (but not limited to) venipuncture, anesthesia, or surgery.

Peri-procedural care requirements include:

• Properly preparing the animal to undergo the procedure humanely;
• Supporting the animal's physiological function during the procedure; and
• Providing additional supportive care to aid the animal in recovering from the procedure.

The investigator has the responsibility to see that staff working with the animals are properly trained not only to perform the procedure humanely but also to provide the necessary supportive care to the animals.

When performing any procedure, such as a blood collection, you should think through the steps that are necessary to protect the animal's welfare. For example, for blood collection, you should limit the volume to the minimum that may be taken safely. That amount may vary depending upon whether a single sample is taken or multiple, chronic collections are done and, with any venipuncture, you should be prepared to care for the animal in the event of trauma to the vein area or excess hemorrhage.

Humane concerns are not limited only to experimental procedures. All aspects of handling should be conducted in such a way as to minimize pain, fear, anxiety and other manifestations of distress. Conversely, the animal's comfort should be made a priority by providing adequate feed, water and environmental conditions.

Refer to your institution's IACUC and attending veterinarian for specific guidelines.

All other factors being equal, swine tend to organize themselves into matriarchal groups of 3-6 sows plus their offspring. In a research environment, swine may be housed singly or in pairs or groups, and in cages or pens.

When housed together, compatibility among cage mates is an important consideration for minimizing inter-animal aggression. When groups are first formed, aggression can be intense for 2-6 hours until a social hierarchy has been established. Animals in stable groups should not be re-mixed into new groups if possible. Females should not be housed with sexually intact males except for breeding.

Animal Welfare Act regulations do not provide specific standards for housing swine, but the Guide does offer guidelines for space and other aspects of swine housing and these may be applied by regulators.

Cages or pens should allow for normal bodily function and protection from injury. The animal should be comfortable and free to make normal postural adjustments and movements. Housing should be secure, durable and in good condition. Cages and pens should be constructed to facilitate cleaning and sanitation. They should have smooth surfaces that are impervious to moisture and have no crevices which accumulate soil.

Flooring should not be so slippery as to predispose the animals or personnel to injury, nor so rough as to cause foot injury or impede sanitation. If slotted floors are used, attention should be given to the size of the openings relative to the foot size of animals to be housed on them to prevent injury to the animals.

Baby pigs are poor thermoregulators and require a very warm thermal environment. The need for external sources of warmth diminish as the pigs mature.

Swine used in research may be obtained from sources that breed specifically for research or from local farm herds or other commercial producers. Animals bred specifically for research often have a more clearly defined health status, known pedigrees and standardized vaccination status than randomly obtained farm animals.

There are a large number of different farm breeds any of which might potentially be used for research. A good source for information about specific swine breeds is available at the University of Oklahoma's Animal Science Department web site.

For biomedical studies, domestic breeds often grow too rapidly and too large. In that case there are a several "mini" and "micro" breeds from which to choose. Some of these include the, Yucatan, Hormel, Goettingen and Hanford varieties. These breeds attain adult sizes that roughly approximate adult human weights and may therefore be more appropriate models for studying certain aspects of human pathology and physiology. Click here for detailed information on some of these breeds.

Ideally, swine should be obtained from herds that meet the standards of the National Specific-Pathogen Free (SPF) Swine Accrediting Agency. This organization provides accreditation for herds that meet established standards as determined by slaughter checks and veterinary inspections every 90 days.

SPF is a proprietary term developed by the above agency and it refers to herds that are certified free of certain specific diseases and infectious agents to include: external parasites, swine dysentery, atrophic rhinitis, pneumonia, pseudorabies and brucellosis. These herds are closed colonies originating from caesarian-derived stock.

An SPF designation doesn't certify pigs free of all disease-causing agents as would be mandatory in pig-to-human xenotransplantation (transplanting tissues between individuals of different species - e.g. pigs to humans), but it does indicate that pigs are of higher quality than those obtained from unaccredited herds. Unfortunately, SPF swine are not always readily available for use in biomedical studies.

The photograph shows the lungs from an animal with enzootic pneumonia, a highly prevalent infection in domestic swine caused by Mycoplasma hyopneumoniae, one of the conditions excluded from certified SPF herds.

Your institutional veterinarian can assist you in finding a reliable source for your animals.

Upon arrival at your facility, your swine should have an acclimation period before they are used in research studies. This period of time allows animals to adapt to a new environment. Effects of transportation stress include alterations in various blood parameters, immune cell function and animal behavior. Swine are particularly susceptible to stress-induced gastric ulcers. If the animals are to be group-housed, they will need a period of time in which to establish a compatible, stable, social hierarchy.

The period of time necessary for biological stabilization will depend on the parameters to be studied. Refer to your institution's attending veterinarian for recommendations that are appropriate for your project. Typically, acclimation periods range from 4 days to 1 week.

Quarantine of new animals aims to prevent transmission of diseases between the new animals and established colonies. There are a large number of swine diseases that may be introduced by new arrivals including (but not limited to) pneumonia and arthritis caused by Mycoplasma spp.; enteric diseases associated with Salmonella, Campylobacter, E. coli, and Serpulina; generalized bacterial infections such as erysipelas or brucellosis; mixed infections like atrophic rhinitis; and viral infections such as Porcine Reproductive and Respiratory Syndrome, Pseudorabies, or Swine Influenza.

The photograph shows a young pig with arthritis caused by a species of Mycoplasma

A quarantine period provides a period for animals to be tested for infectious agents of interest, and to be observed for signs of illness that might have been inapparent at the time of their arrival. It also permits immunizations to be administered if deemed appropriate. Quarantine periods vary in length but usually run one to two weeks.

Acclimation, quarantine and conditioning periods usually run concurrently, although they serve different purposes. Most institutions do not allow experiments on animals while quarantined.

Extended conditioning periods are usually not necessary for swine since, unlike random-source dogs or cats, they are not obtained from a population of animals that may have been stray before they were collected by a vendor and they are generally already in good condition. However, a conditioning period may still be useful to permit animals to recover from shipping stress, adapt to the laboratory diet, and become accustomed to contact with humans.

If your proposed study involves a painful procedure, the protocol form may ask for a method of assessing if the pigs are experiencing pain or distress.

The signs of acute pain and distress can vary according to the nature and location of the pain, the animal's pain threshold, emotional state, and environment. You must know how swine appear and behave normally in order to recognize abnormalities that may signal pain and distress.

In the pig, signs of pain or distress include changes in gait, activity, posture, and attitude. Pigs may vocalize or become aggressive if a sore area is touched or moved, however this is more difficult to interpret since pigs are highly vocal animals normally and squeal in response to positive stimuli (such as feeding) as well as in response to fear or pain.

Behavioral signs of acute pain and distress in the pig may include:

• Hyperactivity, restlessness, nervousness, salivation, anxious facial expression, or self-mutilation.
• Hypoactivity, listlessness, reluctance to move or get up.
• Altered gait, favoring body part. The photo shows a pig that is knee-walking due to foot pain.
• Self-mutilation or licking.
• Aggressiveness when approached or touched.
• Vocalization – either unprovoked or when touched.
• Reduced intake of water and food.
• Loss of body weight.
• Changes in skin or hair coat – dull, dirty or greasy.

A chronic state of pain or distress may be more subtle and difficult to detect. A good knowledge of the animal’s normal appearance and behavior is especially important to recognize chronic pain or distress.

A knowledge of the characteristics of swine is helpful to effectively manage these animals and to plan experimental procedures for their use. Researchers should be aware of the following practical features.

Digestive

The canine teeth of adult swine grow very long and extend from the mouth as tusks. They may need to be clipped periodically to prevent injury to handlers and other pigs.

Pigs are omnivores with a monogastric stomach and digestive physiology that is similar in many ways to that of man. There is a muscular and glandular thickening in the area of the pyloris, called the torus pyloricus, that modulates patency of the pylorus.

The vascular supply divides into an arcade in the subserosa rather than the mesentery, and the colon elaborates a series of spirals that contains the cecum and is called the spiral colon before descending on the left side to become the rectum. The picture demonstrates the spiral colon.

The pancreatic duct enters the duodenum separately and several centimeters distally from the common bile duct, rather than joining it as is the case in humans.

Liver

The liver consists of four lobes and the lobular structures are separated by fine connective tissue that makes them grossly visible. The common bile duct enters the duodenum about 4-5 cm. distal to the pylorus.

Behavior

Pigs are intelligent, inquisitive and assertive animals with a natural preference for social grouping. They typically spend about 80% of their time lying or sitting. Young pigs may exhibit behavioral vices such as nosing the bellies, biting the flanks or chewing the tails of pen-mates. These behaviors can be mitigated to some extent by providing enrichment items for them to chew or play with.

Pigs modulate their thermal environment by behavioral means such as seeking water or mud wallows in the heat, and by huddling in the cold.

Pigs are also highly vocal animals and they emit a wide variety of grunts and squeals in response to social interaction, feeding, fear or pain. They do best when handled carefully and gently and are susceptible to development of peptic ulcer disease in response to sustained stress.

Cardiovascular

The pig heart is anatomically and functionally very similar to the human heart. The coronary artery distribution is similar to man and the pig is susceptible to induces atherosclerosis, making it a popular model for studying the pathology of heart disease and for pre-clinical testing of therapeutic devices and procedures. The photo shows a normal pig heart.

Larynx

The pig has a relatively large larynx that becomes a relatively narrow trachea, so smaller diameter endotracheal tubes must be used for pigs than for dogs of a comparable weight. The long, narrow oropharyngeal cavity with redundent soft tissue, and the presence of a partially obstructing cricoid cartilage ring can make endotracheal intubation challenging in the pig. This is discussed further in the section on anesthesia. The thyroid gland of the pig is situated on the ventral aspect of the trachea at the thoracic inlet rather than near the larynx as in most other mammals.

Skin

The integument of the pig is very similar to that of humans which has made the pig a popular model for studying wound healing, transdermal drug absorption and delivery, phototoxicity and dermal toxicology. The pig has a more firmly attached skin than do other laboratory species, making them less amenable to delivery of fluids or medications by subcutaneous clysis.

Malignant Hyperthermia

The pig shares a metabolic disorder called malignant hyperthermia with man. The condition is genetically mediated by an autosomally dominant gene and is more prevalent in certain breeds such as the Landrace, Yorkshire and Pietrain. The condition is characterized by sudden onset of elevated body temperature and muscle rigidity and untreated it is rapidly fatal. It is precipitated by stress and certain anesthetic and paralytic agents. Susceptible animals can be identified by genetic screening, and should be avoided as biomedical research models.

Pigs without human interaction tend to respond with fear to human presence. Therefore, pigs to be used in biomedical research should be subjected to positive interactions with people to decrease or eliminate the fear response. Pigs also have good memories so unpleasant interactions with people should be balanced with pleasant ones.

Oral medications can be administered in the feed. Pigs don't like bitter tasting materials so such agents should be enclosed in gelatin capsules. If the animal is restrained a "balling gun" can be used.

Certain behavioral characteristics and tendencies can be exploited to advantage when working with swine:

• Pigs will follow other pigs.
• Pigs respond to positive reinforcement. Sometimes they can be trained to submit to a procedure by providing food to occupy their attention.
• A pig's first response to stress is to vocalize and try to escape.
• Pigs tend to "explore" visually and by smell as they move, so patience is preferable to abruptness on the part of the handler.
• Pigs tend to move toward open areas and away from walls, so a "hog board" can be used to advantage when moving them.

The photo shows a portable panel or "hog board" that can be used to help herd pigs or to restrain them in a corner for injections or examination.

As has already been noted, restraint is very stressful to pigs, and once they attain any significant size, it is physically difficult to accomplish. Consequently, the need for restraint should be balanced against the consequences of restraint-associated stress. Chemical restraint may be the best choice in many instances.

When physical restraint is deemed necessary there are a couple of techniques that may be considered.

A snare - a loop of cable or rope attached to a pole - may be effective in very large animals. With the snare attached to the snout, the animal usually pulls backwards against it and effectively restrains itself, for simple procedures such as blood collection. This is not a good technique for smaller animals.

A humane device for restraining small and medium-sized pigs is the Panepinto sling. This is a heavy canvas sheet with openings strategically placed for the limbs and it permits an animal to rest comfortably while restricted from using its legs to escape. This is particularly useful for animals that are chronically instrumented and require restraint periods that are extended beyond a few moments. The photo shows an example of a Panepinto sling with a Yucatan mini-pig. Note: it is very important to acclimate pigs to a sling over time; otherwise they often struggle at first and can harm themselves in the process.

Injections can be administered to swine by the subcutaneous (SC), intramuscular (IM), or intravenous (IV) routes, but pigs don't like injections and so some degree of restraint may be needed to obtain precision of location.

This is particularly true for subcutaneous injections since the skin is relatively firmly attached to the underlying tissues and there is little free subcutaneous space. SC injections are best administered on the dorsal neck, behind the ears or in the flank area.

Pigs are bred commercially for meat and possess a large amount of muscle tissue for IM injection. The best sites are usually the rear leg muscles or the dorsal neck muscles. There is often a layer of back fat, expecially in larger swine that makes IM deposition of drugs less reliable when injected in the back muscles.

Pigs can either be confined into a corner of the pen, using a hog board, or injected while moving free in the pen. In the latter instance, many people find it convenient to use a butterfly needle with the syringe attached to the catheter to minimize chances of the needle becoming dislodged before or during the injection.

Available sites for IV injections are limited in the pig and the ear veins are used most often. Note that ear notching to identify pigs can damage some of these vessels. Alternative sites are the facial vein in well-restrained or the lingual vein in anesthetized animals. The photo shows the blood vessels of the ear.

Blood collection is not difficult in swine with a little practice, but it is complicated by the fact that, with a few exceptions, veins are not as superficial as in dogs and cats and consequently must be accessed by a "blind stick". Pigs are very animated and difficult to restrain manually without stress to the operator and the animal, and risk of injury to the blood vessels, so blood collection is greatly facilitated by chemical restraint.

The blood volume of a pig is approximately 65ml/kg. A maximum, safe volume for a single collection is approximately 8 ml/kg. When using the cranial vena cava a 2-inch, 22g-18g needle is adequate for animals less than 50-60kg. For larger animals a 4-inch needle should be used and for very large animals a 6-inch needle might be required.

Some of the veins that may be used to collect blood from young or adult pigs are shown in the table below. The photo shows the approach to blood collection from the jugular vein or cranial vena cava in a young animal. The pig is being held vertically, head-down, but the technique is equally effective with the chemically-restrained pig in dorsal recumbency (lying on its back).

Blood Collection Sites

Location	Young Pigs	Adults
Vena cava	yes	yes
Jugular vein	yes	yes
Facial vein	yes	yes
Orbital sinus	yes	no
Ear vein	difficult	yes

Terminology used for drugs that affect consciousness and pain perception is not consistent in the literature and is complicated by the fact that some drugs have effects that overlap categories. The terms used here are terms that are commonly used in a research environment and are not meant to be rigidly definitive.

This section includes swine dose rates for the common drugs and drug regimens. If you need to use other drug agents, check with your institution's veterinary staff for assistance in determining a dose rate appropriate for use in pigs.

Postoperative Analgesics

Available in two classes of drugs – the opioids and the nonsteroidal anti-inflammatory drugs (NSAIDs).

Opioids are drugs that derive from the opium poppy or synthetic analogs and that are useful for relieving moderate to severe pain. Depending on the specific agent, they are administered orally, IM, SC, IV or transdermally. Adverse effects include itching, nausea or vomiting and respiratory depression. These agents are federally controlled substances. The following agents and doses have been used in swine:

• Buprenorphine 0.05-0.10 mg/kg IM every 6-8 hours
• Butorphanol 0.1-0.3 mg/kg IM every 4-6 hours
• Oxymorphone 0.15 mg/kg IM every 4-6 hours
• Meperidine 10 mg/kg IM every 4-6 hours

NSAIDS are non-steroidal, anti-inflammatory drugs. These drugs derive from a diverse range of chemical classes but they share an ability to mediate inflammation and relieve mild to moderate pain. Adverse effects may include gastric ulceration, inhibition of platelet aggregation, kidney or liver toxicity. They are not controlled substances. Agents and doses that have been used in swine are:

• Aspirin 10 mg/kg by mouth every 4-6 hours
• Phenylbutazone 4-8 mg/kg by mouth every 24 hours
• Ketoprofen 1-3 mg/kg by mouth every 12 hours

Sedatives

Sedatives may obtund consciousness but in normal doses do not do so sufficiently to ablate the perception of pain or other sensations. When combined with general anesthetics, they may be used to induce "balanced" anesthesia where muscle relaxation, unconsciousness, and analgesia are enhanced. Used by themselves, these drugs may decrease anxiety, fear or excessive activity.

Sedatives that have been used successfully in swine include:

• Diazepam 0.5-10 mg/kg IM or 0.44-2.0 mg/kg IV.
• Midazolam 100-500 mcg/kg IM or IV
• Azaperone 2-8 mg/kg IM
• Acepromazine 0.1-0.5 mg/kg IM

Analgesic Sedatives

Some sedatives also have analgesic effects. When combined with general anesthetics, a balanced anesthesia is attained, and these sedatives enhance analgesia through specific effects.

Certain alpha-2 receptor agonists are sedatives which have analgesic effects. They may induce bradycardia, heart block and hyperglycemia. These agents are not as effective in swine as in other species so they are commonly mixed with other drugs in an anesthetic cocktail, in which their dose rates are reduced. An antagonist may be administered to reverse their pharmacological effects. For doses to be used in anesthetic cocktails, refer to your institutional veterinarian.

• Medetomidine 20-40 ug/kg SC, IM or IV. Reverse with atipamezole (0.1-0.2 mg/kg IV or IM).
• Xylazine 1.0-2.0 mg/kg SC or IM. Reverse with IV administration of yohimbine (50-100 mcg/kg).

Anesthetics:

An anesthetic regimen should be chosen to match the duration of drug effects with the length of the procedure. In particular, short acting agents (and regimens) should be not be used for long procedures because repeat drug administrations, necessary to prolong anesthesia, will produce uneven blood concentrations and therefore periodically inadequate anesthesia. For long procedures, gaseous anesthesia is often the most practical method to sustain uniformly adequate levels of anesthesia.

Endotracheal intubation should be performed when a pig is anesthetized to ensure an open airway. This also provides an avenue for administration of controlled inhalation anesthesia. Endotracheal intubation can be challenging in swine because of their long, narrow oropharyngeal cavity, superfluous soft tissue, and laryngeal anatomy.

Briefly, intubation is accomplished using a laryngoscope blade to depress the tongue and expose the laryngeal opening (Sometimes the blade must be used to free the epiglottis from entrapment behind the soft palate in order to make the laryngeal opening visible). Topical application of lidocaine at this point will help prevent laryngospasm and will ease intubation. An entotracheal tube, with a stylet, is advanced so that the bevel of the tube is parallel with the laryngeal opening. The tube is passed into the larynx and gently rotated to help ease its passage beyond the vocal folds and cricoid cartilage. The balloon tip is then inflated and the tube secured with gauze or tape to the snout.

The photo shows a pig larynx and trachea in saggital section with an endotracheal tube inserted to the level of the vocal folds where rotation of the tube will assist its passage into the trachea.

Inhalation Anesthetics

Because of the ability to provide rapid control of anesthetic depth and consistent anesthesia of long duration, inhalation agents are usually preferable choices for most procedures. Isoflurane is probably the most commonly used agent, but others include: sevoflurane, enflurane, and halothane. Each of these agents has subtle differences from the others in terms of potency, cardiovascular effects, ventilatory effects, and speed of onset and recovery. You should discuss your specific needs relative to these factors with your institutional veterinarian.

Injectable Anesthetics

There are dozens of permutations and combinations of injectable anesthetic agents that have been used with more or less success in swine. Injectable agents are generally best used for inducing anesthesia prior to endotracheal intubation and use of inhalant agents, or for short, minor procedures. A comprehensive list of these regimens can be reviewed in some of the references at the end of this course. The following are some of the agents and combinations that have been used successfully in swine:

• Ketamine is a dissociative agent that is administered IM, SC or IV in dosages ranging from 11-33 mg/kg. By itself, ketamine produces poor muscle relaxation and poor analgesia, so it is usually combined with other agents in pigs.
• Another dissociative agent is tiletamine which is commercially available as Telazol, a proprietary combination of tiletamine with the benzodiazepine zolazepam. Tiletamine is more potent than ketamine and Telazol produces better muscle relaxation than ketamine. Telazol is administered in a dose range of 2.0-8.8 mg/kg, and is usually combined with other agents to produce balanced anesthesia.
• Propofol is an ultra-short acting agent that is available in an oil emulsion that must be administered intravenously. The dosage is 0.83-1.66 mg/kg IV followed by a continuous infusion of 14-20 mg/kg/hr.

Some commonly used injectable anesthetic combinations include:

• ketamine 20 mg/kg + xylazine 2.0 mg/kg IM
• ketamine 33 mg/kg + acepromazine 1.1 mg/kg IM
• ketamine 4 mg/kg + xylazine 4 mg/kg + oxymorphone0.15 mg/kg IM
• telazol 4.4 mg/kg + xylazine 4.4 mg/kg IM
• telazol 4.4 mg/kg + xylazine 2.2 mg/kg + butorphanol 0.22 mg/kg IM

Aseptic technique should be used when performing major survival surgery on swine. This is also required by the Animal Welfare Act (Federal law), but recall that swine are excluded from AWA regulations when used in research relating to food or fiber production, as compared to biomedical research. The standards described here are consistent with the Guide for the Care and Use of Laboratory Animals.

Survival surgery means that the animal regains consciousness after anesthesia. In nonsurvival surgery, the animal is euthanized before recovery from anesthesia.

Major surgery means penetrating and exposing a body cavity such as the chest or abdomen; or producing substantial physical or physiological impairment.

If you will be performing major survival surgery on swine, federal requirements are that:

• The surgery be carried out in a dedicated surgical facility.
• The surgeon must wear cap, mask, and sterile gown and gloves.
• The incision site is appropriately clipped, scrubbed, disinfected, and draped.
• Instruments and surgical materials are sterile.
• The animals receive proper supportive care and monitoring for anesthesia and vital signs through the procedure and afterward.

If you will be performing minor survival surgery, requirements are less stringent than outlined on the previous. According to the Guide, requirements still include: "aseptic technique and instruments and appropriate anesthesia. Although laparoscopic procedures are often performed on an 'outpatient' basis, appropriate aseptic technique is necessary if a body cavity is penetrated."

If you will be performing nonsurvival surgery, it may not be necessary to follow all the techniques outlined on the preceding screen for major survival surgery. According to the Guide, "at a minimum, the surgical site should be clipped, the surgeon should wear gloves, and the instruments and surrounding area should be clean."

Supportive care aims to:

• Maintain the animal's physiological status as nearly normal as possible.
• Minimize animal pain and distress.

Supportive care includes the monitoring of both physiological parameters and analgesia during anesthetic and surgical procedures. Monitoring of vital signs and pain should be conducted throughout the procedure and the recovery period.

Keep in mind that:

• General anesthesia causes disturbances of thermoregulation and other physiological functions.
• Warming devices (e.g., heated tables and pads) are recommended for routine use to maintain the animal's body temperature.Care should be taken to avoid devices that may cause thermal injury.
• During surgery, the animal may experience pain if anesthesia is inadequate at any time during the procedure.
• Postoperatively, the animal may experience pain, discomfort, and distress unless treated with analgesics and appropriate supportive care measures.

Due to the interaction of metabolic factors and drug effects that can cause animal mortality, pigs should receive good supportive care and monitoring during anesthesia, whether or not the procedure involves surgery.

During anesthesia and surgery, the following procedures are recommended.

Supportive Care:

• Provide a source of warmth to the pig from the onset of anesthesia to the end of anesthetic recovery.
• Infuse sterile physiological fluid (warmed to body temperature) to compensate for blood loss during a procedure and depressed fluid intake post-procedure.

Monitoring during Anesthesia:

• Analgesia is best evaluated in the pig by testing jaw muscle tone or by pinching the tail, ear tip or coronary band of the hoof.
• Respiration - gross changes in rate, character of breathing.
• Color of mucous membrane and skin – blue (poor oxygenation), pale (poor blood perfusion).
• Cardiac electrical activity should be monitored if procedures involving open or intravascular heart manipulation are to be done. Pigs are particularly sensitive to developing arrhythmias and may benefit from premedication with amiodarone or bretylium. Operators should be prepared to perform intra-procedural rescue using lidocaine, nitroglycerine or other agents as necessary.

After anesthesia and surgery, the following procedures are recommended.

Monitoring post Anesthesia:

• Pigs must be monitored until fully recovered from anesthesia as indicated by the ability to ambulate and maintain core body temperature.

Monitoring post Procedure:

• Assess appearance, activity, and behavior as indications of pain and discomfort (see lesson Detecting Pain and Distress).
• Assess food and water intake.
• Assess wound repair. Routine use of antibiotics is not indicated after uncomplicated aseptic surgery.

The term euthanasia is derived from Greek and means "good death." Animals should be euthanatized when killed for any purpose, including research. To euthanatize a pig, you must be trained in the concepts of euthanasia, the method to be used, and the proper handling of pigs.

The 2000 Report of the AVMA Panel on Euthanasia lists methods that are acceptable, conditionally acceptable and unacceptable for a large range of species, including swine. This lesson will not cover them exhaustively, but a complete list and discussion of these methods may be reviewed by clicking on the link to the American Veterinary Medical Association.

For swine, acceptable methods include barbiturates, CO2, and potassium chloride only in conjunction with general anesthesia. In biomedical research, it is rarely, if ever, necessary to use other methods, and an intravenous overdose of barbiturates is most commonly used. Commercially prepared formulations of concentrated solutions of pentobarbital sodium are available specifically for euthanasia.

Barbiturate overdose is most effective if the animal has been first sedated with an intramuscular injection of one of the agents or combinations listed in the earlier lesson on Analgesics, Sedatives and Anesthetics for chemical restraint so as to minimize the distress associated with physical restraint.

Unless you have scientific reasons for using other means, you should plan to use a euthanasia method that is accepted by the AVMA Panel Report. The inclusion of conditionally acceptable methods in your protocol may require scientific justification in order to obtain IACUC approval.

The goal of all euthanasia techniques is to cause death in the animal with as little pain or distress as is manageable - the ideal amount is none -and to minimize the distress in people who are observing or performing the procedure. Regardless of the method used, it is important to recall that the person performing the procedure must be proficient in its use.

Federal Laws, Regulations, Policies:

1. Animal Welfare Act, as Amended (7 USC, 2131-2156)
2. Animal Welfare Act Regulations and Standards, Code of Federal Regulations, Title 9, Part 2-Regulations, Sections 2.31-2.33
3. Health Research Extension Act of 1985, Public Law 99-158, November 20, 1985, "Animals in Research".
4. Public Health Service Policy on Humane Care and Use of Laboratory Animals, Revised September, 1986, Reprinted March, 1996
5. USDA Animal and Plant Health Inspection Animal Care Policy Manual
   Policy #11 - Painful/Distressful Procedures
   Policy #12 - Written Narrative for Alternatives to Painful Procedures
6. U.S. Government Principles For The Utilization And Care Of Vertebrate Animals Used In Testing, Research, And Training, Interagency Research Animal Committee

Guidelines:

1. Comfortable Quarters for Pigs in Research Institutions, Department of Animal Science, Colorado State University.
2. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching, FASS Publications.
3. Guide for the Care and Use of Laboratory Animals, National Research Council, 1998.
4. National Center for Infectious Diseases, Center for Disease Control and Prevention (CDC).
5. Occupational Health and Safety in the Care and Use of Research Animals, National Research Council, 1997.

Texts:

1. Flecknell, Laboratory Animal Anesthesia, 2nd Edn., Academic Press, 1996.
2. Fox, Cohen, and Lowe, Laboratory Animal Medicine, Academic Press, 1984.
3. Hawk and Leary, Formulary for Laboratory Animals. 2nd Edn., Iowa State University Press, 1999.
4. Pond and Mersman, Biology of the Domestic Pig, Cornell University Press, 2001
5. Plumb, Beterinary Drug Handbook, 3rd Ed.; Iowa State University Press, 1999
6. Swindle, Surgery, Anesthesia, & Experimental Techniques in Swine, Iowa State University Press, 1998
7. Wolfensohn and Lloyd, Handbook of Laboratory Animal Management and Welfare. 2nd Edn., Blackwell Science. 1998.