Individual difference in faecal and urine equol excretion and their correlation with intestinal microbiota in large white sows

Equol is an end metabolite of daidzein produced by the intestinal microbiota, exhibiting stronger antioxidant and estrogenic activities. It has been proposed that the beneficial effects of soybean/phytoestrogens may be dependent on the intestinal equol-producing ability, i.e. the equol hypothesis. The 'equol hypothesis' has been well applied to human clinical studies. However, the information of equol-producing ability in sows is quite limited. In this study, the individual differences and correlation between equol excretion and intestinal microbiota in large white sows were assayed. The results showed faecal equol levels of 0.14-17.85 mu g/g (coefficient of variation: 61.22%) and urinary equol levels of 0.53-8.19 mu g/mL (coefficient of variation: 54.72%). The levels of equol and daidzein correlated positively in both urine and faeces (P < 0.05). The levels of daidzein and ratio of equol : daidzein in both faeces and urine were significantly higher than equol status (P < 0.01). Cluster analysis of denatured gradient gel electrophoresis patterns showed that faecal samples with similar equol concentrations had similar microbial composition. The Shannon diversity and bands number in gel was significant negatively correlative with faecal equol status (P < 0.001). The population of total bacteria, Firmicutes and Bacteroidetes correlated negatively with faecal equol production (P < 0.05). Positive correlations were found between urinary equol production and the population of bacteroidetes and methanogen-producing bacteria (P < 0.05), demonstrating for the first time the relationship between equol excretions and gut interspecies H-2 transfer in sows.