Effect of genetic line and steroidogenic capacity on response to dietary supplementation of biochar to control fat androstenone levels in boars

Boar taint, an unpleasant odor in heated pork, is caused primarily by androstenone accumulation in fat. Previous research demonstrated that biochar (BC), a charcoal-based adsorbent, can reduce androstenone accumulation in the fat when used as a dietary additive. The objective of this study was to compare the effectiveness of BC as a dietary treatment for boar taint in two genetic lines of boars from Alliance Genetics Canada (AGC) and Pig Improvement Company (PIC), and examine the influence of steroidogenic capacity on treatment response. All boars were fed a 5% BC diet for 4-wk starting at a bodyweight (BW) of 75.25 ± 1.42 kg and 111.10 ± 0.86 d of age (DOA), followed by a 2-wk recovery period where BC was removed from the diet. Plasma androstenone, estrone sulfate (E1S), and growth performance parameters were measured weekly, and fat androstenone was measured biweekly. We found that 71% of PIC boars and 47% of AGC boars never developed boar taint, as the fat androstenone concentrations remained below the threshold of 1 μg/g throughout the trial. Of those with the capacity to develop boar taint, 89% of AGC boars responded to BC treatment, compared to 67% for PIC. However, no differences in plasma or fat androstenone levels were observed between the two genetic lines. Additionally, all growth performance parameters were not different between AGC and PIC boars except gain: feed (G:F) during the treatment period and average daily gain (ADG) during recovery, where PIC boars performed better (P = 0.001). Plasma E1S concentrations measured at approximately 130 kg live weight were used to classify boars as either high (plasma E1S > 16 ng/mL) or low steroidogenic capacity (plasma E1S ≤ 16 ng/mL). High steroidogenic capacity boars had greater plasma E1S concentrations (P < 0.05) across all time points compared those with low steroidogenic capacity, although growth rates remained not different between groups. In both genetic lines, boars that never developed boar taint as well as those responded to BC treatment consisted of a mix of high and low steroidogenic capacity animals, while boars that did not respond to BC treatment were exclusively high steroidogenic capacity. These results suggest that steroidogenic capacity may help to predict BC treatment response, although additional research is needed to identify genetic and biological markers associated with treatment success in order to effectively tailor BC treatment to animals most likely to benefit.