Net flux of folates and vitamin B12 through the gastrointestinal tract of sheep

Abstract

In Trial 1, three wethers were equipped with ruminal and caecal cannulas, catheters in the right ruminal and caecal veins and a mesenteric artery, as well as blood flow probes around the right ruminal and caecal arteries. Blood samples were collected every 15 min from 30 min before to 60 min after the injection of 9 μmol of folic acid and vitamin B12 per kilogram body weight (BW) in the rumen and after injection of half this dose in the caecum. There was a net release of these vitamins from the rumen shortly after the injection (P < 0.05). In Trial 2, four wethers were equipped with a ruminal cannula, catheters in the right ruminal, mesenteric and portal veins and a mesenteric artery and blood flow probes around the right ruminal and the mesenteric arteries and the portal vein. Blood samples were taken 30 and 60 min before, and 30, 60, 120, 180, 240 and 300 min after the intraruminal injection of 0.32 g of folic acid and 0.98 g of vitamin B12. In Trial 3, blood samples were taken from two wethers previously used in Trial 2, before and 10, 40, 70 and 100 min after the intraruminal injection of 0.32 g of folic acid. These intraruminal injections led to a net release of the vitamins from the mesenteric and portal-drained viscera (P ≤ 0.17) but also from the other gastrointestinal tissues, probably mostly from the duodenum. Therefore, in sheep, the main site of absorption for folic acid is the proximal intestine whereas the absorption of vitamin B12 appears in a more distal part of the small intestine. Key words: Sheep, folic acid, vitamin B12, absorption