The bile acid (BA) pool size is significantly increased in lactating rats. Bile acids were harvested from control female rats (C) (n = 8), rats at day 20 of gestation (G d20) (n = 4), and at days 6 (n = 4), 10 (n = 3), 14 (n = 6), and 19–23 (n = 4) of lactation (postpartum, PP). The bile acids were measured by HPLC analysis. Shown are the means ± SD. *P < 0.05 and **P < 0.001 vs. control female rats, determined by one-way ANOVA, followed by Bonferroni's multiple comparison post hoc test. d, day; BW, body weight.