Cryptorchidism is a congenital condition where one or both of a male pig’s testicles do not descend into the scrotum. This is a common issue in swine production, with incidence rates varying between 2% and 12%. Because the testes should be fully descended at birth, this condition presents challenges related to the animal’s health, reproductive future, and the economics of pork production.
Why Cryptorchidism Occurs in Pigs
The normal development of a male pig involves the descent of the testes from inside the abdomen down into the scrotum. This complex migration is guided by anatomical structures and hormonal signals during fetal growth. The process can be disrupted, causing a testis to be retained in the abdominal cavity, the inguinal canal, or in a subcutaneous position. When this process fails for one testis, it is unilateral cryptorchidism; when both fail, it is bilateral.
Genetics is the primary driver of cryptorchidism, as the condition is a heritable defect passed down from parents. While the exact mechanism involves multiple genes, it is a recognized hereditary issue. Research shows that specific breeding pairs can produce a higher percentage of cryptorchid males, and inbreeding also increases the likelihood of the condition.
Beyond genetics, hormonal factors are involved in testicular descent. Hormones like testosterone and Müllerian inhibiting substance guide this process, and any disruption can interfere with migration. Environmental factors may also play a part, including chemical exposure or maternal vitamin A deficiency during gestation, though these links are less defined than genetic causes. The left testis is more frequently retained, possibly because its developmental path is longer.
Detecting Cryptorchidism in Piglets
Identifying cryptorchidism is done through physical examination of piglets, often during the first few weeks of life or at castration. The most direct method is palpation, which involves carefully feeling the scrotum to confirm the presence of two testicles. In a normal piglet, both should be palpable from birth, so an empty or partially empty scrotum is the clearest indicator.
A visual inspection can also reveal asymmetry in the scrotal area, suggesting the absence of a testis. A retained testis can be located in several places along its descent path. Common locations include high in the inguinal region, where it may be felt as a small lump, or deep within the abdominal cavity, where it cannot be detected by external palpation.
For producers, this check is a routine part of processing new litters. It is important to distinguish cryptorchidism from a temporary retraction of the testes, which can happen in very young piglets. In a true cryptorchid animal, the testis will not descend on its own. Advanced tools like ultrasound can be used to locate abdominally retained testicles, which is useful before a surgical procedure.
Consequences for Affected Pigs and Farms
The most significant consequence for pork producers is the risk of boar taint, an unpleasant odor and flavor that can develop in the meat of intact male pigs. Retained testicles, even if not fully functional, can still produce the hormones responsible for this taint. Carcasses affected by boar taint may be devalued or condemned, leading to direct financial losses.
From a reproductive standpoint, the condition impacts fertility. Pigs with both testicles retained (bilateral cryptorchids) are sterile because the higher temperature inside the body prevents sperm production. Those with only one retained testicle (unilateral cryptorchids) may still be fertile, but their sperm production can be reduced. These animals should not be used for breeding because they will pass the genetic defect to their offspring.
Attempting to castrate a cryptorchid pig also introduces complications. The procedure is more complex and invasive than a standard castration, especially if the retained testicle is in the abdomen. This often requires veterinary intervention and increases the risk of surgical complications, raising costs and potential health issues for the animal.
Approaches to Managing Cryptorchidism
The primary management strategy is careful identification and action during castration. It is necessary to confirm that both testicles have been removed. For a cryptorchid pig, the descended testis is removed normally, while the retained one must be located and surgically excised. This procedure, a cryptorchidectomy, is more expensive and may require a veterinarian if the testis is abdominal.
Culling is a common practice for managing the genetic aspect of this condition. Boars identified as cryptorchid are removed from the breeding pool to prevent them from passing the trait on. Producers may also choose to cull the sire and dam that produced cryptorchid offspring, especially if they show a pattern of doing so. This selective pressure helps reduce the condition’s incidence within the herd.
While surgical correction to move the retained testicle into the scrotum is possible, it is not an economically viable practice in commercial pig farming. The most effective long-term approach is genetic selection. By carefully selecting breeding stock and keeping detailed records, producers can actively work to eliminate the genes responsible for cryptorchidism from their herds.