The effects of condensed tannins on the net flux of skatole and indole across the mammary gland and their secretion in milk of lactating ewes fed fresh sulla (Hedysarum coronarium)

Abstract

The effects of condensed tannins (CT) in fresh Sulla (Hedysarum coronarium) on the net flux of skatole and indole from the gastrointestinal tract to the mammary gland were investigated in ewes during mid to late lactation. Twelve ewes were prepared with catheters in the mesenteric artery and the mesenteric, portal, hepatic and mammary veins. A transonic flow probe was fitted around the pudic artery for measuring mammary blood flow. All ewes were fed Sulla (2000 g DM d-1; 80 g CT d-1) for 28 days. Half the ewes were orally drenched (4 times per d) with polyethylene glycol (PEG; 160 g d-1 in water) to remove the effects of CT whilst the remaining ewes received water. Milk yield was measured twice daily for three weeks. Milk samples were taken at the morning and evening milkings and pooled for measuring skatole and indole concentration. Overall, the CT in Sulla did not affect (P>0.05) milk yield and milk fat yield. Milk indole and skatole concentration and yield tended to be lower (P<0.1) with the CT treatment at day 14 but overall, only skatole parameters were reduced by the CT. On day 28, blood flow was measured and blood samples were taken to determine concentration of indole and skatole in plasma so their net plasma flux could be calculated. The plasma flow across the mammary gland was unaffected (P>0.05) by CT. The CT in Sulla decreased the concentration of indole (P<0.05) and skatole (P<0.1) in the mesenteric artery and mammary vein, but did not affect (P>0.05) the net flux of indole and skatole across the mammary gland. Results from this study indicate that CT in a Sulla diet reduces the concentration of skatole in plasma and milk, and that circulating skatole exchange into milk, but that it does not appear to be an active process.