The effect of dietary supplement with 17% high-amylose barley (Hordeum vulgare, HAB) 'Karmose' on boar taint was studied on 72 crossbred entire male pigs (Sus scrofa domestica) Swedish Yorkshire dams x Swedish Landrace sires). All pigs were fed the same commercial diet (12.4 MJ metabolised energy (ME) per kg, digestible crude protein (CP) 13.5%) twice a day until the average live weight (LW) in the pen reached 100 +- 11.8 kg. Then, 32 out of 72 pigs received an HAB diet. Half of these pigs received HAB for 14 days and the other half for 28 days. The pigs were slaughtered at an average LW of 122.3 +- 8.6 kg (age 167.2 +- 7.5 days). The HAB diet did not affect performance, carcass and meat quality characteristics, and puberty status, but reduced plasma skatole levels in the pigs (least squares means, 3.6 vs. 2.0 ng mlE-1, P = 0.037). However, this diet failed to reduce skatole, indole and androstenone levels in fat (P is greater than 0.10). Nevertheless, it is desirable to continue investigation of HAB to optimise the feeding procedure to improve efficiency of HAB effect on fat skatole levels. Additionally, validation of a greater amount of HAB in the diet should be performed.

Accumulation of skatole levels in porcine fat tissue is a major reason for boar taint, an objectionable odour in meat from entire male pigs. In contrast to males, female pigs do not accumulate skatole in increased amounts. Hepatic metabolism is critical for the regulation of skatole. Cytochromes P4502E1 (CYP2E1) and P4502A6 (CYP2A6) are key enzymes involved in skatole metabolism. The objectives of this study were to evaluate the effects of gender and hCG stimulation on the activities of CYP2A6. Liver samples were taken at slaughter and analyzed for skatole concentrations, and for activities of CYP2E1 and CYP2A6. It was found that female pigs expressed higher CYP2E1 activity whereas activity of CYP2A6 did not differ between sexes. Skatole levels in the liver were higher in male pigs than in female pigs. Neither skatole levels nor enzyme activities were affected by hCG stimulation. It was concluded that the incidence of boar taint may depend on both the amount of skatole reaching the liver, and the activities of enzymes involved in skatole metabolism.

Tryptophan is a precursor for the production of skatole and indole in the large intestine of pigs. Accumulation of these compounds in adipose tissue causes on objectionable odour in meat from entire male pigs. Potential market impact illustrates the importance in developing an accurate method of determining skatole and indole content in adipose tissue. In the present study, a method is described for determination of skatole and indole concentrations by liquid chromatography combined with mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The optimization of chromatographic and APCI conditions is reported. This method showed excellent linearity over the concentration range tested (from 10 to 1000 ng mlE-1 of liquefied fat for both skatole and indole).