In pigs, the testicle initially develops within the abdomen. Prior to birth the testicle descends via the inguinal canal into the scrotum. If the testicle fails to descend the pig is described as a cryptorchid pig or retained testicle pig. If marketed with the retained testicle there is a severe financial penalty. When the testicle does descend normally the tissues of the inguinal ring subsequently tighten up in order to prevent the abdominal organs from descending into the inguinal canal (inguinal hernia) or into the scrotum (scrotal hernia). Inguinal hernias can sometimes be bilateral but usually occur only on one side. Hernias are 5 times more common on the left side than on the right side. In most cases it is portions of the small intestine that will descend into the hernia. The intestine contained in the hernia can be damaged at castration, it may become entrapped within the hernia and it may become twisted and cut off blood supply to the intestine. None of which are good outcomes.
Some genes have been related to inguinal / scrotal hernia. If a single boar or a family of boars that are close relatives have an abnormally high incidence of hernia then the probability of a genetic component increases. Sometimes the elimination of the suspect boar, boar family and other close relatives can reduce the incidence. There may be a genetic contribution from the sow herd. The occurrence of the defect in the pure lines that make up the crossbred pig can sometimes be lower that that of the crossbred offspring. This suggests that there may be a detrimental heterosis cause to this condition. It is possible to have two commercial herds using the same dam and boar lines but having significantly different incidences of hernia. This suggests that there may be predisposing genotype by environmental interaction that can alter the incidence. It is also known that adjusting the castration technique can reduce the incidence of herniation. Cutting the spermatic cord rather than pulling it to break it will reduce the incidence of inguinal hernia. Leaving the spermatic cord in the inguinal canal may be somewhat analogous to leaving the “Dutchman’s finger in the dyke.” Some farms have become very proficient at applying a tape truss bandage when detecting a scrotal hernia after castration. The bandage when tightly applied temporarily prevents herniation while some connective tissue is laid down within the area of the inguinal canal. When the bandage is removed the connective tissue prevents herniation.
Although many of the genes associated with inguinal / scrotal herniation have been identified it is not well understood how these genes actually allow for expression of the hernia. These Brazilian researchers wanted to investigate the expression profile of a set of genes potentially involved with inguinal / scrotal hernia and more specifically with the inguinal ring tissue. Tissue samples from the inguinal ring/canal of normal and scrotal hernia-affected male pigs at approximately 30 days of age were used. Relative expression analysis was performed using qPCR to confirm the expression profile of 17 candidate genes previously identified in an RNA-Seq study.
The researchers found the following:
- Myosin heavy chain 1 (MYH1), Desmin (DES), and Troponin 1 (TNNI1) genes were differentially expressed between groups and had reduced levels of expression in the hernia affected animals.
- These genes encode proteins involved in the formation of muscle tissue, which appears to be important for increasing the resistance of the inguinal ring to abdominal pressure. Abdominal pressure will be a force that will attempt to push abdominal organs into the inguinal canal and therefore stronger muscle tissue in the area of the inguinal ring can push back on this abdominal pressure.
Take Home Messages:
- The downregulation of muscular candidate genes in the inguinal tissue clarifies the genetic mechanisms involved with this anomaly in its primary site.
Reference: William Raphael Lorenzetti , Adriana Mércia Guaratini Ibelli , Jane de Oliveira Peixoto , Igor Ricardo Savoldi , Marcos Antônio Zanella Mores , Gabrieli de Souza Romano , Kamilla Bleil do Carmo , Mônica Corrêa Ledur The downregulation of genes encoding muscle proteins have a potential role in the development of scrotal hernia in pigs Mol Biol Rep . 2024 Jul 18;51(1):822. doi: 10.1007/s11033-024-09766-1.
