Effects of duodenal infusion of sunflower oil on β-glucuronidase activity and enterolactone concentration in dairy cows fed flax meal

• Microbial β-glucuronidase increases absorption of mammalian lignans.
• Abomasal infusion of sunflower oil has no effect on β-glucuronidase activity.
• Dietary flax meal decreases fecal β-glucuronidase activity.
• Flax lignans metabolism is not affected by sunflower oil in the small intestine.

Microbial β-glucuronidase activity is important for the absorption of enterolignans. This study was performed to evaluate the effects of dietary flax meal and abomasal infusion of sunflower oil (SO) on activity of β-glucuronidase in ruminal fluid and feces, and concentration of enterolactone (EL) in ruminal fluid, plasma, urine and milk. Eight rumen fistulated lactating Holstein cows were assigned to a double 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments: (1) control diet with no FM (CO); (2) diet containing 137 g/kg flax meal (FM); (3) CO and infusion of 250 g SO/d in the abomasum; and (4) FM and infusion of 250 g SO/d in the abomasum. Activity of β-glucuronidase in ruminal fluid was similar among diets. Cows fed the FM diets had lower fecal β-glucuronidase activity than those fed the CO diets. Infusion of SO lowered fecal β-glucuronidase activity. Supplementation with FM increased EL concentration in plasma, urine and prefeeding ruminal fluid, and SO reduced EL concentration in ruminal fluid before feeding. Dietary FM and SO infusion had no effect on milk EL concentration. Overall, the metabolism of flax lignans and the absorption of enterolignans were not affected by the presence of SO, a rich source of n-6 fatty acids, in the intestine as indicated by similar concentrations of EL in ruminal fluid (pool of 2, 4 and 6 h postfeeding), plasma and urine. These results suggest that the effect of fat on the metabolism of lignans may differ between results observed in the present experiment with ruminant animals and those obtained in previous studies with non-ruminant animals.