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Dietary hydrolysable tannins from chestnut have the potential to reduce the risk of boar tainted carcasses
Recent in vitro incubation studies of swine caecal inoculum with different concentrations of hydrolysable tannins (HT) suggested an inhibitory effect of HT on the total activity of caecal bacteria. These findings are of interest especially in the production of entire males where the synthesis of skatole (S) and indole (I), 2 compounds responsible for boar taint, could be reduced in the colon by dietary means. Results of a recent in vivo study revealed the potential of HT to reduce the incidence of boar taint. Thus, the goal of the present study was to determine possible threshold levels of supplemented dietary HT on S and I tissue deposition. For the study 44 Swiss Large White entire males from 11 litters were selected at 59.4 kg BW and assigned within litter to 1 of 4 treatments: unsupplemented control finisher diet (T0); finisher diet supplemented with 1.5 (T15), 3.0 (T30) or 4.5% (T45) chestnut powder. All pigs were reared in one pen equipped with 4 automatic feeders. They had ad libitum access to the assigned diets. The animals were weighed weekly and individual feed intake was monitored daily. At 103.5 kg BW, pigs were slaughtered and organ weights as well as carcass characteristics were assessed. In addition, concentrations of androstenone (A), S and I levels were measured in the backfat using HPLC. Despite similar feed intake, T45-pigs tended (P<0.10) to grow slower than T15-pigs, with intermediate values for T0- and T30-pigs (0.80, 0.92, 0.88, 0.83 kg/d). T45- and T30-pigs were less (0.34 kg/kg each; P<0.05) feed efficient than T0- and T15-pigs (0.38 and 0.37 kg/kg). Compared to the T0-group, lean meat percentage was lower (P<0.05) in carcasses of boars from the T15-group (56.7 vs. 58.4%), with intermediate values for the T30- and T45-group (57.3 and 57.5%). Weight of the liver, kidney and salivary gland were lighter (P<0.10) in the T45- compared to all other groups. Due to large variability in the A, S and I levels in the backfat, no significant (P>0.27) dietary effects were observed. However, taking into account the suggested boar taint thresholds for A (<1 ppm) and/or S (<0.25 ppm), fewer T45- than T0-, T15- and T30-pigs were above these thresholds (2 vs. 5, 6, 5). In conclusion, the current data show that despite the slight negative effect of the highest dietary HT supply on growth performance incidence of boar taint could be lowered at the highest HT inclusion level.
Keywords:
boar taint, hydrolysable tannin, pig