Quick Summary
Phenotype: Affected piglets exhibit congenital, generalized edema because their lymphatic system failed to develop appropriately. Clinical presentation commonly includes marked abdominal distension (often referred to as “water belly”), and widespread subcutaneous and tissue fluid accumulation. On necropsy, pulmonary hypoplasia (markedly reduced lung development) is also observed. This condition reflects a disruption of the normal lymphatic function during pregnancy, resulting in an inability to properly regulate fluid balance during fetal development.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, ALY = Alymphoplasia (“water belly”) variant
Breeds appropriate for testing: Chester White and derivatives
Explanation of results:
• Pigs with N/N genotype will not have this inherited form of alymphoplasia (“water belly”) and cannot transmit this disease allele to their offspring.
• Pigs with N/ALY genotype are not expected to be affected by this inherited form of alymphoplasia (“water belly”) but are carriers. They may transmit this ALY allele to 50% of their offspring. When two carrier animals are bred, 25% of their offspring are predicted to be affected.
• Pigs with ALY/ALY genotype are stillborn.
Sample Collection
Pig DNA tests are carried out using cells from the roots of a hair sample (roughly 20-30 hairs).
Hair samples should be coarse hair from the body, tail area, between toes, or inside an ear.
Instructions
1. Clean (use comb if possible) by removing all loose hair and foreign matter.
2. Use fingers or pliers to grasp approximately 8-10 hairs close to the skin and pull. Pull (do NOT cut) hair strands. Examine the end of hair strands for presence of root bulbs. Hair roots are necessary for DNA testing. If the majority of hair strands lack the root bulbs, discard hair and start again.
3. Repeat until you have approximately 20-30 hairs with root follicles attached.
4. Place the 20-30 hairs with root follicles attached in the envelope and seal with the animal’s ID written on the envelope.
5. Repeat steps 1-4 for each additional animal being sampled.
Note:
- Hair should be dry.
- If hair has excess dirt and debris, please brush out if possible before pulling hairs for sample.
- Do not cut the hair! The roots contain the DNA for testing.
- When sampling several animals in the same session, make sure that there are no hair strands in your hands to reduce the possibility of sample contamination. Clean hands and/or pliers if possible.
Alymphoplasia, also referred to as “water belly”, is a heritable autosomal recessive disorder that affects pigs, in which affected piglets are typically stillborn and display severe fluid accumulation. A genetic variant associated with this condition has been identified by Dr. Jonathan Beever at the UTIA Genomics Center for the Advancement of Agriculture, University of Tennessee. Dr. Beever has shared the information with the VGL prior to publication so our laboratory can develop a genetic test to assist breeders in avoiding the production of affected piglets. Additional details will be provided following publication of the scientific study.
Testing recommendations:
Genetic testing for this condition allows breeders to identify carrier animals and make informed mating decisions to reduce the risk of producing affected piglets. Pigs with one copy of the variant allele (N/ALY) are expected to be phenotypically normal but are carriers and can transmit the variant to approximately 50% of their offspring. When two carrier animals are mated (N/ALY × N/ALY), there is a 25% chance of producing affected (ALY/ALY) piglets, a 50% chance of producing carriers (N/ALY), and a 25% chance of producing unaffected, non-carrier (N/N) offspring. To prevent affected litters, matings between known carriers should be avoided. Carrier animals can be retained within a breeding program if managed appropriately, for example by mating animals that are carriers of the variant (N/ALY) exclusively to animals that are homozygous for the normal version of the gene (N/N).