Figure 3

Feeding antimicrobials (AMA) to pigs alter the synthesis of secondary bile acids and the profile of bile acids (BA) in a tissue-specific manner. Two independent cohorts of piglets were weaned and fed for 35 days cereal-based diets medicated with combinations of AMA, which were either zinc oxide, amoxicillin, and colistin (ZAC) or zinc oxide, chlortetracycline, and tiamulin (ZCT) at dosing levels routinely used for preventing bacterial enteritis and stimulating pig growth. Control pigs (CON) received no AMA. The concentration of BA was measured via UPLC-MS in samples taken on days 34 and 35. Data from the two experiments were combined in the figure. (A,B) Bile salt hydrolase activity (assessed by treating colonic digesta with labeled tauro-cholic-d5 acid and measuring the formation of cholic acid-d5 via UPLC-MS) and (C,D) primary to secondary BA ratios in colonic contents of pigs fed CON or medicated (ZAC and ZCT) diets. (E–J) Relative concentration of HCA (E,F), CDCA (G,H), and LCA (I,J) in liver, plasma, and intestinal mucosa of pigs fed ZAC (E,G and I) or ZCT (F,H and J). Data were analyzed with ANOVA. Least squares means ± SEM are plotted, ^*P < 0.05, ^**P < 0.01, n = 10–12, nd = not detected.