Skatole levels in pigs selected for high lean tissue growth rate on different dietary protein levels

Skatole content in backfat was studied in purebred Yorkshire pigs, selected for lean tissue growth rate on either a low-protein diet containing yellow peas, or a conventional high-protein diet. The present study included 162 entire males and 91 females from generations 1, 2 and 4 in the selection experiment. The animals were slaughtered at approximately 103 kg live weight. Entire male pigs from the low-protein line had on average higher skatole levels than males fed the high-protein diet or females fed either diet (P ≤ 0.001). No difference was found between the sexes from the high-protein line. Only 2.8% of males in the high-protein line exceeded the threshold value suggested for skatole (≥ 0.20 ppm), which should be compared with 23.3% of the males in the low-protein line. In one replicate of the low-protein line as many as 10 out of 20 of the male pigs exceeded the threshold value. These 10 male pigs were half- or full-sib progeny of two sires that were half-brothers. The difference in skatole level between male pigs from the two selection lines might depend on an interaction between feed composition and some genetic influence. The results suggest that the genetic effect for skatole deposition may be due to a recessive gene - probably a major gene - having a pronounced effect especially under certain environmental conditions.