This is a not uncommon condition seen in both gilts and boars up to six months of age. Mild forms can sometimes be seen in individual mature boars indifferent herds. It has been described in pigs as young as 3 – 4 weeks of age where there may be a genetic predisposition.
As the animal approaches maturity its body changes shape and it starts to give the appearance of two different pigs joined together at the middle. The back above and behind the ribs becomes increasingly dipped and the back above the middle and rear abdomen becomes humped. The condition is abnormal and unsightly but, in the absence of other diseases, the pigs remain healthy and normal in every other way.
In some cases it is a developmental condition and probably environmental although what factors in the environment cause it are not known. The affected farms may have a significant proportion of their growing breeding stock with it but closely related breeding stock on other farms all develop normally. In herds where the condition is common there may be a boar conformation involvement. Record and observe progeny from suspect boars. It has also been associated with excessive riding of boars and back damage. Early onset of puberty has been implicated in boars.
In severe cases partial or complete paralysis may be seen. Such animals should be destroyed. Mortality is usually low.