Breeding Responsibly
Avoid Hereditary Defects
Breeding mini pigs is a responsibility that should be taken seriously. Loving an animal or having friends/family that want one of his/her babies is not a valid reason to breed your mini pig. A lot of research, consideration, and thought should go into every breeding pair. Failure to breed responsibly may result in piglets that are deformed, fail to thrive, or suffer life long consequences of the ill-paired breeding. As Carla Glutting of Little Rooters Mini Pigs says, “Don’t breed it just because it breathes”.
A hereditary condition or genetic defect is described by The Pig Site as a condition that is inherited by the boar’s or sow’s genes. Boars and sows that throw defective genes should be spayed or neutered to prevent tainting the mini pig gene pool. NEVER breed a pig that is a carrier for a genetic defect. Very often a pig with a single genetic defect also carries other hereditary conditions. Sometimes it is not clear which parent is throwing the defective genes. In this case, trial and error may be needed. Clear records of breedings and the offspring will help you determine which parent(s) are the carriers of the genes. When breeders or piglets die suddenly and without obvious cause, it is important to have a necropsy done to determine the cause of death. If the cause is genetic, then spaying and neutering the breeder carriers will improve the long term health of your breeding lines.
As breeders of mini pigs, it is our responsibility to ensure only the best of the best are bred. We are lucky to have a very diverse gene pool to choose breeding pigs from. If you are looking to add breeding stock to your herd, consider an AMPA Registered Breeder. Search the map of AMPA Registered Breeders, or get to know the breeders in the Meet the Breeder blogs. Tracking breeding pairs, litters, health, and defects in the AMPA Mini Pig Registry Database will help determine which pigs or pairings should be bred, and which should not. The two most prevalent genetic defects in swine are cryptorchidism and inguinal/scrotal hernias according to Genetics Selection Evolution. All efforts should be made to eliminate these defects from all breeding herds.
Hereditary Defects in Mini Pigs
Do Not Breed List
Inguinal or Scrotal Hernias
Cryptorchidism Retained Testicle
Atresia Ani / Anal Atresia
Porcine Stress Syndrome
Inverted Teats
Umbilical Hernia
Cleft Lip / Palate
Hermaphroditism
Arthrogryposis
Epitheliogenesis Imperfecta
Inguinal or Scrotal Hernias – High Risk/Common
Inguinal or scrotal hernias are seen too often in mini pigs. The incidence of these hernias is far higher than in commercial farm hogs. Inguinal or scrotal hernias occur from a weakness of the musculature surrounding the inguinal canal, allowing the intestines to drop into the scrotum. This is seen as a bulge at the rear end or sometimes between the legs. In some cases, the hernia develops before neutering. In other cases, the hernia ruptures during or shortly after the neuter procedure. It is important to always have mini pigs neutered by the care of a veterinarian that will sew the inguinal ring closed to prevent this hernia. If hernias do happen, close observation should be taken to remove any carriers from the breeding stock. This genetic defect causes great pain to the pigs, potentially death, a higher cost of veterinary care, higher risk neuters, and puts new owners in a very bad place if they have adopted an intact pig. NEVER breed a pig that is a suspected carrier of hernias.
Inguinal or Scrotal Hernia Further Reading:
American Association of Swine Veterinarians
Genetics Evolution Selection Journal
The Agricultural College of Norway
Cryptorchidism – High Risk/Common
Cryptorchidism, also referred to as “crypto” is a well known genetic defect that is seen in swine and many other animals. Carriers of this genetic defect should be altered to prevent further breeding of the defect. Cryptorchidism is a condition in which one or both testicles fails to descend to the scrotum. The retained testicle(s) remain in the body cavity. Healthy mini pigs, unlike dogs, are born with both testicles descended. If one or both testicles is not descended, a call to the veterinarian is in order. The cost to neuter a pig with cryptorchidism is substantially higher than an uncomplicated neuter, the procedure is more painful, and carries more surgical risk as the veterinarian must enter the abdominal cavity to find the retained testicle. If left intact, a crypto boar may be fertile to impregnate a sow with the defective genes. Undescended testicles have a far higher incidence of testicular cancer, which would remain undetected for a longer period of time as they are out of view. Undescended testicles also are more susceptible to testicular torsion and inguinal hernias. In humans, undescended testicles are reported to cause abdominal pain. NEVER neuter a cryptorchidism leaving the undescended testicle behind. When neutered, both testicles must be removed. Never breed a cryptorchid boar, and never assume he is infertile. Many rescuers and adopters have sadly assumed a boar was neutered when he had an undescended testicle, resulting in a litter suffering from this genetic defect.
Cryptorchid Further Reading:
North Carolina State University
Genetics Evolution Selection Journal
Anal Atresia – High Risk/Severe
Anal Atresia or Atresia Ani is a fatal condition where pigs are born without an anus. In some cases, the anus is present but malformed or non functioning. This condition often proves fatal early in life either before weaning or shortly after weaning as the piglet starts to eat solid foods. Always check for fully functioning anus before adopting out piglets. In females, sometimes the digestive tract will reroute the feces to exit the vagina. This often goes unnoticed for some time by unaware breeders or new pig parents. Only when the piglet suffers loose stool for some time does the pig parent take the piglet to the veterinarian where atresia ani is diagnosed. In some cases, surgery is possible to correct the defect and create a new opening for the stool. In all cases, the genetic component should be closely evaluated to prevent this fatal defect from hurting more pigs.
Anal Atresia further reading:
The Agricultural College of Norway
North Carolina State University
Porcine Stress Syndrome (PSS) – Sudden Death
Porcine Stress Syndrome is a nonpathogenic, neuromuscular disorder that causes sudden unexplained death in pigs, usually triggered by natural stressors (weaning, transport, vaccinations, etc). The defective dystrophin gene has been identified by USDA scientists. This stress disorder has been mapped by molecular biologist Dan Nonneman and his colleagues in the USMARC Reproduction Research Unit. Porcine Stress Syndrome causes several changes within the body including muscle weakness, abnormal heart rate, and an inability to tolerate anesthesia. Pigs will Porcine Stress Syndrome may have muscle tremors, elevated body temperature, signs of heat stress even in cold weather, rapid or erratic heart rate, rapid and labored breathing, blanching and reddening of the skin,collapse, muscle rigidity, or sudden death.
Scientists have shown that piglets are most susceptible around 8 weeks old. This is a very dangerous time frame for a piglet to endure stress as they are spayed, neutered, weaned, and moved to a new family. The defective gene is most common in males inheriting PSS from their mothers.
If you have piglets that do not handle anesthesia well or die unexpectedly when stressed, it is highly recommended to have necropsies done to determine the cause of death. If Porcine Stress Syndrome is suspected, testing of your breeding herd should be done to eliminate the gene from your breeding line.
There are currently atleast two laboratories that will genetically test for this disorder with a mailed in sample.
Porcine Stress Syndrome Further Reading:
Dr. G Mitchell & Dr. J. J. H. Heffron
North Carolina State University
Inverted Teats – Concern for Breeding Stock
Inverted teats are nipples that fail to project from the gland. In other words, the tip of the nipple is hidden. This hereditary defect is a major concern in breeding stock as they impair the mother’s ability to feed her piglets. Inverted nipples do not allow milk to flow naturally, thus affecting the piglet’s nutrition, health, and survivability. A spayed/neutered pet pig will not be affected by inverted teats, but the genetic line should be watched closely. If this defect is passed down it could affect other breeder pigs as a carrier gene. This is an example of breeding for the welfare and integrity of the breed as a whole.
North Carolina State University
Umbilical Hernia
Umbilical hernias are protrusions that occur when abdominal connective tissue fails to close around the umbilical ring. This presents as a bulge or growth around the umbilical area. This hernia may be very mild as only a small raised area or in more extreme cases there will be a very large bulge as the intestines press out of the abdominal cavity. Umbilical hernias are suspected as hereditary defects in some cases, although more often this condition is brought on by infection of the umbilical cord. Records of breedings will help to track and understand the genetic component, if any, in your breeding lines.
Umbilical Hernia further reading:
American Association of Swine Veterinarians
North Carolina State University
Cleft Palate / Cleft Lip
Cleft palate and cleft lip are congenital oronasal fistulas. These defects of the mouth are often, but not always, genetically passed down from parents. Other causes of cleft palate or cleft lip are nutritional or toxin ingestion during pregnancy. In pigs, swine, cleft palates are thought to be associated with consumption of certain plants, including lupine species, wild parsnip, poison hemlock, and the wild tobacco tree. Neurologic exams should be performed on affected piglets to rule out other defects or problems that often accompany cleft lip/palate such as hydrocephalus. These conditions are apparent at birth. The majority of affected piglets are euthanized or die of their condition shortly after birth.
Cleft Palate / Cleft Lip further reading:
Hermaphroditism
Hermaphroditism is an interesting defect in which an individual pig has both male and female gender parts. Studies have shown that pigs have a higher rate of hermaphroditism than other domestic animals. Hermaphrodite pigs are genetically female with male parts. It is estimated that 0.5 to 1% of a seemingly normal female herd will actually be hermaphrodites. Besides the obvious deformation, there is a higher risk of other genetic defects. Therefore, if a hermaphrodite piglet is born it is important to look for any genetic links or abnormalities.
Hermaphroditism further reading:
Characterization of True Hermaphrodite
North Carolina State University
Canadian Journal of Genetics and Cytology
Intersexes in Swine: A Problem in Descriptive Anatomy
Arthrogryposis
Arthrogryposis is a hereditary disease that affects the joints. A piglet with arthrogryposis will be born with stiff and crooked limbs. See photo here. This is one of the most common congenital defects in piglets. When two or more areas of the body are affected it is referred to as Arthrogryposis multiplex congenital (AMC).
Arthrogryposis further reading:
Epitheliogenesis Imperfecta
Epitheligenesis imperfecta is a common genetic defect in swine appearing as the absence of areas of skin. Instead of healthy skin, these lesions appear at birth as shiny red areas. Infection of the lesions is of great concern. Breeding pigs producing affected piglets should be removed from the breeding program.
Epitheliogenesis Imperfecta further reading:
In Conclusion
The American Mini Pig Association is the first database of its kind that will collect and store the health information of breeding stock and pets along with records of illness, birth defects, and cause of death. The hope is to use this data to improve the quality of mini pigs lives, allow for research of illness, and prevent birth defects, and unnecessary deaths.The more we are able to learn about these amazing animals, the more we can improve their lives. With facts and study comes betterment of the breed. The more we know, the more we can learn!
Learn more about the American Mini Pig Association or become a Breeder Member to register your mini pigs
in the official AMPA Mini Pig Registry.
