In many countries, male pigs are castrated to prevent boar taint, but this practice raises concerns about animal welfare and reduces the production efficiency of pork. The objective of this study was to develop dietary manipulations to prevent boar taint. We evaluated the effectiveness of adding activated carbon (AC) or Tween-60 (Tween; polyoxyethylene sorbitan monostearate) to pig finishing diets to reduce levels of androstenone (AND) and skatole in plasma and fat of entire male pigs. Boars (159 ± 2 days of age at the start of the experiment) were fed diets supplemented with either 5% AC or 5% Tween for 28 days followed by either 14 or 28 days of recovery. Plasma samples were collected at experimental days 0, 7, 14, 21, 28, 42 and 56, and backfat biopsies were taken at experimental days 0, 28, 42 and 56. Feeding AC significantly (P < 0.05) reduced the levels of AND in plasma by day 28 compared to day 0 and by day 42 in fat compared to day 0. AC treatment also decreased levels of oestrone sulphate (E1S) in plasma by day 7 compared to day 0. Treatment with Tween significantly decreased (P < 0.05) the levels of plasma AND by day 28 from levels at day 0. Tween treatment did not significantly affect levels of fat AND or plasma E1S compared to day 0; however, fat AND levels decreased between days 28 and 42 following treatment with Tween (P < 0.05). Levels of plasma E1S, plasma AND and fat AND for control boars remained constant throughout the experiment. Skatole plasma concentrations were very low and did not vary significantly (P > 0.05) from day 0 for any treatment, but fat skatole levels decreased by day 42 in the Tween treatment group. Importantly, there was no difference in growth rate between the control and experimental groups. We conclude that adding AC or Tween to finishing diets for boars can reduce the levels of plasma and fat AND, but further work is needed to confirm the effects of these treatments on reducing fat skatole levels.

Boar taint, an off-odor and an off-flavor in the meat from some uncastrated male pigs, is due to high levels of the testicular steroid hormone, androstenone, and the indole, skatole. Thus far, there are no known methods for controlling both androstenone and skatole through dietary means. We tested the adsorbent agents, cholestyramine (CH), activated carbon (AC), tween-60 (Tween), bentonite (BNT) and polyvinylpolypyrrolidone (PVPP) for binding androstenone, estrone (E1), estrone sulfate (E1S) and skatole from buffer solutions in an in vitro system. The goal was to determine the potential utility of these binding agents as feed additives to control boar taint. Michaelis–Menten analysis was utilized to determine the effectiveness of the adsorbents. At pH 7.4, E1S was bound to AC and CH with the highest Bmax (maximum binding), whereas Tween and AC had the greatest Bmax for E1. The Bmax for skatole at pH 7.4 was highest for AC, CH and PVPP. AC had a higher Bmax for androstenone than CH and Tween. The Bmax values at pH 3.0 with E1S for AC and CH were essentially 100%, whereas the binding of Tween to E1S at pH 3.0 decreased by 49.5% from binding at pH 7.4 (P < 0.05). The Adint values, which represent efficiency of binding, illustrated that AC bound E1, androstenone and skatole with greater efficiency than the other binding agents at pH 7.4, whereas AC bound E1S as efficiently as CH. We conclude that AC was the most effective adsorbent agent for binding E1, E1S, androstenone and skatole in vitro, followed by CH, Tween, PVPP and lastly BNT. These adsorbent agents may be useful for binding boar taint compounds in in vivo studies to decrease the risk of boar taint.