Abstract
BackgroundBoar taint is the undesirable smell and taste of pork meat derived from some entire male pigs. The main causes of boar taint are the two compounds androstenone and skatole (3-methyl-indole). The steroid androstenone is a sex pheromone produced in the testis of the boars. Skatole is produced from tryptophan by bacteria in the intestine of the pigs. In many countries pigs are castrated as piglets to avoid boar taint, however, this is undesirable for animal welfare reasons. Genetic variations affecting the level of boar taint have previously been demonstrated in many breeds. In the study presented in this paper, markers and haplotypes, which can be applied to DNA-based selection schemes in order to reduce or eliminate the boar taint problem, are identified.ResultsApproximately 30,000 SNPs segregating in 923 boars from three Danish breeds; Duroc, Landrace, and Yorkshire, were used to conduct genome wide association studies of boar taint compounds. At 46 suggestive quantitative trait loci (QTL), 25 haplotypes and three single markers with effects were identified. Furthermore, 40% of the haplotypes mapped to previously identified regions. Haplotypes were also analysed for effects of slaughter weight and meat content. The most promising haplotype was identified on Sus scrofa chromosome 1. The gain in fixed effect of having this haplotype on level of androstenone in Landrace was identified to be high (1.279 μg/g). In addition, this haplotype explained 16.8% of the phenotypic variation within the trait. The haplotype was identified around the gene CYB5A which is known to have an indirect impact on the amount of androstenone. In addition to CYB5A, the genes SRD5A2, LOC100518755, and CYP21A2 are candidate genes for other haplotypes affecting androstenone, whereas, candidate genes for the indolic compounds were identified to be SULT1A1 and CYP2E1.ConclusionsDespite the small sample size, a total of 25 haplotypes and three single markers were identified including genomic regions not previously reported. The haplotypes that were analysed showed large effects on trait level. However, little overlap of QTL between breeds was observed.
Highlights
Boar taint is the undesirable smell and taste of pork meat derived from some entire male pigs
30,000 single nucleotide polymorphisms (SNPs) segregating in 923 boars from three Danish breeds; Duroc, Landrace, and Yorkshire, were used to conduct genome wide association studies of boar taint compounds
Using SNPs genotyped in three different Danish pig breeds using the porcineSNP60 BeadChip we aim to identify genomic regions associated with skatole, androstenone, indole as well as the S/I index, which is a skatole equivalent measured by the slaughterhouse containing both skatole and indole
Summary
Boar taint is the undesirable smell and taste of pork meat derived from some entire male pigs. Skatole is produced from tryptophan by bacteria in the intestine of the pigs. 3-methylindole, called skatole, is a metabolite of tryptophan metabolism and is produced by intestinal bacteria in the hindgut of the pigs [1]. Androstenone, a more urine smelling compound is accumulated in adipose tissue. It is biosynthesised from cholesterol in boar testes (reviewed in [2]). It was previously found that levels of both compounds are linked to sexual maturity of male pigs [3] and that there is a relationship between their metabolisms [4]. The heritability of levels of both compounds is substantially ranging from 0.23 to 0.55 for skatole and from 0.49 to 0.67 for androstenone in the Landrace and Duroc breeds [3,7] but the level of accumulated compound varies between breeds [8]
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