ThePigSite Pig Health
Hereditary and Congenital Defects (Developmental abnormalities)(39) Hereditary (genetic) and congenital diseases are quite common in swine and cover a range of conditions. The term "Hereditary" means that the condition was inherited by the piglet from the sow's or boar's genes. The term "Congenital" means that is present at birth but implies it is a development abnormality that occurred during the growth of the foetus while in the uterus, rather than an hereditary defect or abnormality. However some developmental abnormalities are not evident at birth, (for example, an inguinal hernia) and develop at a later stage. They are described as delayed developmental abnormalities. If a congenital defect occurs frequently and is related to a particular line or breed then it is likely to be hereditary.
Defects in the piglet can arise form nutritional causes, poisoning, infectious agents or spontaneously due to abnormal metabolism, as well as hereditary defects.
Most hereditary or congenital defects remain at a low incidence because breeding programmes cull affected animals. Sometimes however, a boar can be identified as being associated with a higher incidence of an abnormality than usual. A typical example would be umbilical hernia. (This condition can also be precipitated by abdominal pressure).
Embryo mortality varies considerably both between breeds and individuals and heredity plays an important but as yet ill-defined part. In most herds, records show that congenital malformations range from 0.5 to 2.5% with an average of approximately 1.5%. However, if all the defects were recorded then levels would approach 3%. Common developmental defects are described in Fig.2-13, the causes of which are often multifactorial in origin.
Another type of problem that occurs at birth is difficulty in farrowing associated with a small or abnormal development of the pelvis.