Introduction

Exotic swine breeds aren't just for zoos anymore! Although the most commonly kept member (outside of a production facility) of the suid family (Sus scrofa )is the pot-belly pig, there are many feral swine (European wild hog x domestic hog), wart hogs (Phacochoerus africanus) and collared peccaries (family: Tayassuidae; species: Tayassu tajacu) living in private homes. Other species that may be encountered in exotic animal collections include the African Red river hog (Potamochoerus porcus), and the Babirussa (Babyrousa babyrousa), bearded pig (Sus barbatus) and Javan warty pig (Sus verrucous) from South East Asia and white-lipped peccary (Tayassu pecari) from Central and South America.

Physical Restraint

Pigs are highly intelligent and sensitive animals and whenever possible, should be trained for routine husbandry procedures. Most species are food motivated and enjoy a good "tummy rub" and thus can fairly easily be trained to stand, sit and lie down on command. Physical exam, hoof trim and possibly blood collection are procedures that could be trained in a pig. However pigs are also a prey species and have a number of effective defense mechanism some of which make them very dangerous. All species have canine teeth that manifest as tusks of various shapes and lengths. Depending on species and sex, tusks can be knife sharp. Pigs do bite but when using their tusks they swing their heads to the side such that the tusk becomes a slashing weapon. Pigs also have a compact bullet shaped, dense body mass that they will not hesitate to use to flatten you as they try to escape. Physical restraint can be challenging, however with the proper equipment and pharmaceutical agents, immobilization and anesthesia are straight forward.

Piglets or small tame, pigs can be held for physical exam. Most pot-belly pigs can be flipped onto their backs for an exam and to perform non-painful procedures such as hoof or tusk trims, vaccination or blood collection. One person can flip a small pig but a heavier or longer bodied pig may require 2 people. To flip a pig, one person grasps the pig from above, behind the shoulders and lifts it up and onto its butt. The other person then cradles and supports the hips as the pig is gently lowered onto its back. One person then straddles the pig using their legs as supports to maintain the pig in dorsal recumbency while the other person performs the procedure. Most pigs will vocalize loudly at first and some will not stop. It is important to monitor the pig for signs of hyperthermia and respiratory distress as dorsal recumbency is an aversive position for a pig.

Pigs can also be temporarily pinned against a wall with a baffle board, placed in a chute or suspended in a sling. When cornered pigs will try and go under, over or through whatever is in their way. This can be dangerous to both humans and pigs. Pigs are not made to jump and can easily fall backwards suffering trauma to the rear limbs, hips and back. Pigs should not be grabbed and restrained or lifted by their limbs. In pot-belly pigs studies have shown that in addition to their chondrodystrophic skeletal confirmation, they have incomplete ossification of the humeral condyles which appear on radiograph as an intracondylar vertical lucency (similar to the condition described in cocker spaniels).⁴ Pot-belly pigs can suffer articular fractures of the distal, medial humeral condyle following relatively minor trauma. Sub-clinical condylar fractures with resulting degenerative joint disease are commonly seen.

Chemical Restraint

Chemical immobilization can be delivered via hand injection or dart. I prefer to hand inject pigs in the skin of the neck directly behind the ear. The skin in this area is thin and there is relatively little subcutaneous fat. Research in laboratory settings indicates that subcutaneous injections appear to cause less pain with no variability of drug absorption or clinical effect. In domestic swine, pot-belly pigs, peccaries and European wild hog breeds, adult boars have dermal plates which cover the lateral aspect of their shoulders and lateral aspect of the proximal portion of the rear leg. As the skin is extremely thick in these areas, they should be avoided when injecting or darting boars.

Table 1 lists published drugs and dosages for anesthesia in the exotic pigs. Telazol and Xylazine cocktails are frequently listed for general anesthesia. Studies indicate that tiletamine and zolazepam are both eliminated more slowly in pigs than in other species¹ frequently resulting in prolonged and stormy anesthetic recovery; characterized by swimming and paddling motions with repeated attempts by pigs to right themselves. My preferred combination is medetomidine, butorphanol and midazolam. This cocktail has been used extensively in all species of exotic swine and provides excellent anesthesia and analgesia and is fully reversible. Concentrated solutions of all 3 of these pharmacological agents are available thus greatly decreasing injection volume. Initial bradycardia from the medetomidine usually improves throughout the procedure and hypoxemia can be corrected with supplemental oxygen via mask for short procedures. This combination provides sufficient relaxation for intubation.

Preoperative Preperation

A pre-anesthetic workup is advised but usually not practical as collecting a blood sample in an un-anesthetized pig can be challenging and auscultation of the heart and lungs is often impossible due to loud vocalizations by the patient.

Adult pigs should be fasted for a minimum of 12 hours. If the pig is fed or has access, and eats alfalfa or other hay, then it should be withheld from the diet for a minimum of 2-3 days prior to anesthesia. The hay seems to delay gastric emptying and I have had a number of pigs vomit large amounts of partially digested alfalfa even though they were fasted for 12 hours.

Pigs can be weighed in a kennel or trained to stand on a scale.

Monitoring

Standard anesthetic monitoring equipment can be used on pigs. Pulse oximeter probes can be clipped to the lower lip, tongue, ear, nipple or vulva. IV catheters (20 or 22 gauge) can be placed in the auricular veins which are located on the dorsolateral aspect of the ear, cephalic or mammary vein. If the ear vein is used, roll gauze can be placed in the ear to provide support and the catheter glued and then taped in place. Pigs appear to tolerate this fairly well, thus the catheter can be left in place if continued fluid therapy is required post-operatively. Blood pressure monitors can be placed on the front and rear limbs.

In domestic swine studies indicate that ocular and pupillary responses do not appear to be useful indicators of anesthetic plane in pigs, rather jaw tone, lack of response to a "pinch and increased heart rate and blood pressure should be used as indicators of depth of anesthesia.

Although some species are often obese, pigs do not have a heavy hair coat and are prone to hypothermia while under anesthesia. During prolonged sedation or while under general anesthesia, pigs should receive supplemental heat and intra-operative and post-operative body temperature should be closely monitored.

Pigs also are prone to hypoglycemia under anesthesia even in animals that have not been fasted. Serum glucose values of < 50 mg/dl have been recorded. Administration of 50% dextrose (2g/kg) has been used to correct the hypoglycemia.² After minor procedures, I offer small amounts or fruit to pigs as soon as they can sit up.

Intubation

Pigs are obligate nasal breathers and the epiglottis of the pig is long compared to the dog, thus allowing anesthesia or supplemental oxygen, via mask even when the mouth is open. A mask designed for dogs can be used but the clear, soft, pliable, plastic cat masks (A.M. Bickford, Inc., 12318 Big Tree Rd., Wales, NY, U.S.A.) can easily be "buttoned" onto the snout creating a snug fit. Using these masks allows access to the mouth while still providing supplemental oxygen or anesthetic gas. Small, young or extremely tractable pigs can readily be masked down with isoflurane or sevoflurane. Standard dog masks can be used in smaller animals and a gallon heavy plastic bottle can be modified into a face mask for larger individuals.

Intubation is uncomplicated with the correct length laryngoscope blade and a well trained assistant. I have found that a 10" or 12" Miller style blade (A.M. Bickford, Inc., 12318 Big Tree Rd., Wales, NY, U.S.A.) will allow intubation of all sizes of pot-belly pigs. Pigs can be intubated while positioned in sternal or dorsal recumbency. In sternal recumbency, the upper jaw is held open utilizing gauze or string by an assistant. The tongue can be grasped and the epiglottis flipped down with the tip of the blade in a scooping motion. The endotracheal tube is advanced with a slight twisting motion and the tube tied in place behind the tusks and around the snout. If the pig is intubated in dorsal recumbency then the laryngoscope blade is advanced at a 45° angle toward the ventral aspect of the pig. This will straighten the laryngeal opening and allowing visualization of the glottis.⁶ Pigs are prone to laryngospasm. If the tube does not pass relatively easily then increasing anesthetic depth and applying a topical anesthetic may be helpful.

Analgesia

Clinical assessment of pain in domestic laboratory pigs is gauged by the following observations; decreased food and water consumption; hyperactivity and or restless / nervous behavior; vocalization / avoidance or aggressive behavior; listless behavior and failure to rise when people approach the pen; self mutilation of excessive licking or rubbing; altered gait or abnormal posture; and changes in skin texture and color.⁵ Although developed in order to monitor pain in laboratory pigs these are a good starting point for assessing pain in exotic suid and peccaries.

Providing analgesia to pigs is straight forward. In domestic swine studies indicate that pre-emptive (pre-operative or intra-operative analgesia leads to improved analgesia and a shorter recovery time.⁶ The non-steroidal drugs carprofen, meloxicam and flunixin meglumine are labeled in Europe for once a day dosing in swine. Ketoprofen and etodolac are also shown to be effective in swine.⁶ Due their omnivorous feeding strategy, most pigs will readily accept products formulated for oral use in dogs. The opiates morphine, fentanyl and meperidine when administered IM only provide 1-2 hrs of analgesia and application of fentanyl patches have produced variable results in domestic swine and are currently not recommended for pain control.⁶ Research facilities that perform minor to major surgeries on pigs recommend the opioid Buprenorphine (0.01 - 0.05 mg/kg) for 8-12 hours of potent analgesia, combined with local anesthetic infiltration at the incision site. For minor procedures, postoperative pain, or if primarily anti-inflammatory action is required, the NSAID carprofen 2mg/kg SID is recommended.⁶

Pot belly pigs are extremely prone to arthritis and oral Carprofen and meloxicam are easily administered and anecdotal reports indicate that they are beneficial. In geriatric animals with severe arthritis where NSAIDS no longer provide clinical relief I have had success with long term oral prednisone at (0.4-0.8 mg/kg, SID, BID or q 2days).

Euthanasia

Tiletamine/Zolazepam reconstituted with 1ml of (100 mg/ml) Ketamine and 1ml of (100mg/ml) Xylazine dosed IM at 1 ml per 50 to 100 # followed by pentobarbital IV or IC.

Table 1^(2,3,6)

References

1.  Kumar A.H., J. Mann and R.P. Remmel. 2006. Pharmacokinetics of tiletamine and zolazepam (Telazol) in anesthetized pigs. J Vet. Pharmacol. Therap. 29: 587-589.

2.  Morris, P.J. and A.L. Shima. 2003. Suidae and tassyuidae (wild pigs, peccaries). In: Fowler M.E. and R. E. Miller (eds.) Zoo and Wild Animal Medicine. Elsevier, St. Louis, Missouri. Pp 586-602.

3.  Padilla, L.R. and J.C.H. Ko. 2007. Non-domestic suids. In: West, G., D. Heard and N. Caulkett (eds.) Zoo Animal and Wildlife Immobilization and Anesthesia. Blackwell Publishing, Ames, Iowa. Pp 567-578.

4.  Samii, V.F. and W.J. Hornof. 2000. Incomplete ossification of the humeral condyle in Vietnamese pot-bellied pigs. Vet Radiol Ultrasound. Mar-Apr; 41 (2):147-53.

5.  Swindle, M.M. 2008. Pain Assessment in Swine. Tech. Bull. Sinclair Research Center, Inc., Columbia, MO, USA. (http://www.sinclairresearch.com).

6.  Swindle, M.M. 2006 Anesthesia and analgesia in swine. Tech. Bull. Sinclair Research Center, Inc., Columbia, MO, USA. (http://www.sinclairresearch.com).