Abstract
BackgroundInguinal and scrotal hernias are of great concern to pig producers, and lead to poor animal welfare and severe economic loss. Selection against these conditions is highly preferable, but at this time no gene, Quantitative Trait Loci (QTL), or mode of inheritance has been identified in pigs or in any other species. Therefore, a complete genome scan was performed in order to identify genomic regions affecting inguinal and scrotal hernias in pigs. Records from seedstock breeding farms were collected. No clinical examinations were executed on the pigs and there was therefore no distinction between inguinal and scrotal hernias. The genome scan utilised affected sib pairs (ASP), and the data was analysed using both an ASP test based on Non-parametric Linkage (NPL) analysis, and a Transmission Disequilibrium Test (TDT).ResultsSignificant QTLs (p < 0.01) were detected on 8 out of 19 porcine chromosomes. The most promising QTLs, however, were detected in SSC1, SSC2, SSC5, SSC6, SSC15, SSC17 and SSCX; all of these regions showed either statistical significance with both statistical methods, or convincing significance with one of the methods. Haplotypes from these suggestive QTL regions were constructed and analysed with TDT. Of these, six different haplotypes were found to be differently transmitted (p < 0.01) to healthy and affected pigs. The most interesting result was one haplotype on SSC5 that was found to be transmitted to hernia pigs with four times higher frequency than to healthy pigs (p < 0.00005).ConclusionFor the first time in any species, a genome scan has revealed suggestive QTLs for inguinal and scrotal hernias. While this study permitted the detection of chromosomal regions only, it is interesting to note that several promising candidate genes, including INSL3, MIS, and CGRP, are located within the highly significant QTL regions. Further studies are required in order to narrow down the suggestive QTL regions, investigate the candidate genes, and to confirm the suggestive QTLs in other populations. The haplotype associated with inguinal and scrotal hernias may help in achieving selection against the disorder.
Highlights
Inguinal and scrotal hernias are of great concern to pig producers, and lead to poor animal welfare and severe economic loss
The most significant regions were found on SSC2, with a multipoint Non-parametric Linkage (NPL) score of 3.16 at marker SW834, and on SSC15 which showed an NPL score of 3.47 at marker SW919
The affected sib pairs (ASP) method tests for markers linked to genes affecting deformity status, while the Transmission Disequilibrium Test (TDT) method tests for markers that are both linked to these genes and associated with a particular trait on a population level
Summary
Inguinal and scrotal hernias are of great concern to pig producers, and lead to poor animal welfare and severe economic loss. An inguinal hernia describes a situation where hernial contents are present in the inguinal canal, whereas scrotal hernia refers to a situation where hernial contents are present in the scrotum In these conditions, most frequently the distal jejunum and ileum pass through the vaginal ring and enter the inguinal canal. In many cases the undescended testes are associated with a patent processus vaginalis because the processus vaginalis does not obliterate unless the testis reach the scrotum [5] This particular form of inguinal and scrotal hernias is correlated with the occurrence of cryptorchism [1], and is a concern for the pig breeding industry as well
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