Absorption and secretion of 65Zn in the stomach and intestinal tract of sheep exchanging digesta via duodenal re-entrant cannulas.

The absorption and secretion of 65Zn in the stomach and intestinal tract regions was studied in sets of two and three sheep which were exchanging digesta via re-entrant cannulas in the proximal duodenum. One sheep from each of the three three-sheep sets was dosed intraruminally with the radioisotope. One sheep from the three two-sheep sets received an intravenous dose. Measurements of 65Zn in blood plasma from intraruminally dosed sheep showed that there was no apparent absorption from the stomach region. Measurements from sheep receiving radioactive digesta intraduodenally showed that mean apparent absorption of 65Zn was 0.07 and mean true absorption was 0.103. There was a large variation in endogenous recycling of 65Zn into the stomach region. Secretion of 65Zn into the stomach and intestinal regions in the intravenously dosed sheep of the two-sheep sets was calculated on the basis of total recovery over 10 d in the digesta and faeces. The present study showed that for every 1 molecule Zn secreted into the stomach region, 2.1 molecules were secreted into the intestinal tract region.