Revealing genetic relationships between compounds affecting boar taint and reproduction in pigs1

Abstract

Boar taint is characterized by an unpleasant taste or odor in intact male pigs and is primarily attributed to increased concentrations of androstenone and skatole and to a lesser extent by increased indole. The boar taint compounds skatole and indole are produced by gut bacteria, metabolized in the liver, and stored in the fat tissue. Androstenone, on the other hand, is synthesized in the testis along with testosterone and estrogens, which are known to be important factors affecting fertility. The main goal of this study was to investigate the relationship between genetic factors involved in the primary boar taint compounds in an attempt to discover ways to reduce boar taint without decreasing fertility-related compounds. Heritabilities and genetic correlations between traits were estimated for compounds related to boar taint (androstenone, skatole, indole) and reproduction (testosterone, 17β-estradiol, and estrone sulfate). Heritabilities in the range of 0.47 to 0.67 were detected for androstenone concentrations in both fat and plasma, whereas those for skatole and indole were slightly less (0.27 to 0.41). The genetic correlations between androstenone in plasma and fat were extremely high (0.91 to 0.98) in Duroc and Landrace. In addition, genetic correlations between androstenone (both plasma and fat) and the other sex steroids (estrone sulfate, 17β-estradiol, and testosterone) were very high, in the range of 0.80 to 0.95. Furthermore, a genome-wide association study (GWA) and a combined linkage disequilibrium and linkage analysis (LDLA) were conducted on 1,533 purebred Landrace and 1,027 purebred Duroc to find genome regions involved in genetic control of the boar taint compounds androstenone, skatole, and indole, and sex hormones related to fertility traits. Up to 3,297 informative SNP markers were included for both breeds, including SNP from several boar taint candidate genes. From the GWA study, we found that altogether 27 regions were significant at a genome-wide level (P < 0.05) and an additional 7 regions were significant at a chromosomal level. From the LDLA study, 7 regions were significant on a genome-wide level and an additional 7 regions were significant at a chromosomal level. The most convincing associations were obtained in 6 regions affecting skatole and indole in fat on chromosomes 1, 2, 3, 7, 13, and 14, 1 region on chromosome 6 affecting androstenone in plasma only, and 5 regions on chromosomes 3, 4, 13, and 15 affecting androstenone, testosterone, and estrogens.

Influence of housing and season on pubertal development, boar taint compounds and skin lesions of male pigs

“…It is stored in the fat tissue and its concentration increases during the pubertal development. Our data show significant correlations between fat androstenone and the plasma levels of oestradiol measured during rearing and at slaughter as well as the plasma level of testosterone measured during rearing in agreement with the previous experiments (Zamaratskaia et al, 2004;Grindflek et al, 2011). Low correlation between plasma testosterone at slaughter and fat androstenone in our data may be explained by the high impact of stress on plasma testosterone, whereas a potential impact of stress on fat androstenone might be delayed, taking into account the delay in the increase between plasma and fat as shown after hCG stimulation (Bonneau et al, 1982).…”

A single nucleotide polymorphism in the CYP2E1 gene promoter affects skatole content in backfat of boars of two commercial Duroc-sired crossbred populations

“…Grindflek, Meuwissen, et al, 2011;Ramos et al, 2011;Tajet, Andresen, & Meuwissen, 2006) support the hypothesis of a major genetic influence on skatole levels in pigs. Even more, Lundström et al (1994) postulated already in the mid 1990s that a recessive gene might affect skatole deposition in the backfat.…”

A performance test for boar taint compounds in live boars

“…The use of molecular methods may allow selection for specific genes that affect only androstenone metabolism without affecting other sex hormones. In a genome scan by Grindflek et al (2011), quantitative trait loci (QTL) affecting skatole and indole did not seem to affect any other traits examined; however, all significant QTLs affecting androstenone identified also affected other sex hormones with one exception.…”