The effects of thiosalicylic and hydroxyethylethylenediaminetriacetic acids on the absorption and excretion of 54Mn and 65Zn in the duodenally dosed sheep.

Abstract

Nine sheep, each prepared with a single cannula in the ascending duodenum and a reentrant cannula in the terminal ileum were fed a purified diet deficient in manganese and zinc for a period of 1 month. The sheep were then divided into three equal groups and duodenally dosed with a mixture containing MnSO4, ZnSO4, 54Mn, 65Zn, and water (control), thiosalicylic acid (TSA), or hydroxyethylethylenediaminetriacetic acid (HEDTA). Blood and ileal digesta were sampled for 24 h and total urine and feces were collected for 14 days after dosing. Plasma uptake of 54Mn 1 h after dosing was more than threefold higher in the HEDTA-dosed sheep than in other sheep, indicating higher absorption of 54Mn. This was accompanied by a lower flow of 54Mn through the terminal ileum during the first 12 h after dosing. However, total 14-day urinary and fecal excretion of 54Mn and 65Zn were apparently higher in the HEDTA-dosed sheep than in other sheep, each approaching 100% of the dose. Excretion of 54Mn and 65Zn in TSA-dosed sheep was apparently higher than in control sheep. Plasma uptake 65Zn was higher in TSA-dosed sheep and lower in HEDTA-dosed sheep than in control sheep. However, total 14-day excretion of 65Zn in feces and urine was slightly higher in TSA-dosed than in control sheep. It was concluded that chelation of Mn and Zn with HEDTA or TSA would aggravate rather than alleviate a Mn or Zn deficiency in sheep.