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Newsletter February 2015

Breeding boars to smell well. KU Leuven and ILVO identify a gene linked with lower risk for boar taint

Selecting for pigs with a lower genetic predisposition to produce boar taint could be a big leap forwards for producing male pigs without surgical castration. In an ILVO-KU Leuven study, a marker gene for boar taint was identified. Pigs selected against boar taint showed fewer boar taint compounds in blood and fat, better slaughter quality and a higher meat percentage.

pigsSocial pressure to ban surgical castration of male piglets is growing. One possible sustainable alternative is raising entire males, but the meat of some entire boars produces an off-odour when heated (“boar taint”). Researchers are now working to find ways to raise entire males without boar taint.

For the last four years, ILVO worked with KU Leuven to find a genetic marker linked to the occurrence of boar taint. The study has yielded a promising marker: a polymorphism of the MC4R gene. In an experiment with animals selected for presence of this polymorphism, a clear link between the genotype and the level of boar taint components was observed. The concentration of the backfat boar taint components (skatole, indole and androstenone) was clearly lower in selected animals. In blood samples taken at different times in the feedlots, decreased serum skatole levels were also observed. Despite these observations, trained experts reported no significant differences between the boar taint odour scores after smelling heated fat of the boars.

Pigs selected against boar taint had a lower daily feed intake. This resulted in a lower daily growth in boars but not in gilts. This slower growth led to lower fat deposition and therefore better carcass quality measurements such as meat percentage (64.4% versus 62.8%) and a wider ham.

Because production of androstenone and male hormones is linked, the researchers assessed whether selection against boar taint has effects on behaviour and puberty. As a consequence of their slower growth, selected boars had the same age at the start of puberty but a lower bodyweight. The percentage of boars that reached puberty at slaughter did not differ significantly between selected and non-selected boars. No differences in plasma testosterone concentrations were observed. A higher percentage of selected gilts had reached puberty at slaughter (31% versus 8%). Pigs selected against boar taint showed more active behaviour like playing and manipulating the environment. They had slightly more skin lesions on their anterior and back area, which could possibly be caused by aggressive and sexual behaviour, although this could not be confirmed by behaviour observations. No effect on lameness was observed.

In conclusion, the project led to the identification of a promising marker for reduced occurrence of boar taint. Although boar taint cannot be ruled out completely, this marker is promising, especially because the selected animals showed favourable production characteristics and fertility properties. Still, management measurements could be necessary to reduce undesirable behaviour.

Title: Boar taint: selection as a sustainable alternative for castration of piglets
Funding: IWT
Term: 2009 – 2014
Partners: Division of Gene Technology, KU Leuven and ILVO
Contact: Alice Van den Broeke, Marijke Aluwé, Frank Tuyttens, Sam Millet