Factors affecting the digestibility, absorption and retention of calcium, oxalate, ethylen-diamine-tetracetic acid (disodium salt), nitril triacetic acid, lysine and protein quality

Abstract

Studies have been made in rats about the nutritive utilization of calcium, judged by the following indexes: efficacy of calcium absorption by small intestine in anaesthetized rats, calcium digestibility coefficient, increase in body calcium and calcification of the femur bone. We study the influence on these parameters of the following variables: protein quality, lysine content in the diet, sodium oxalate, ethylendiamine tetracetic acid disodium salt (EDTA-Na2) and nitril-triacetic acid. Sodium oxalate greatly decreased the efficacy of calcium absorption in small intestine (4.4 %) and calcium digestibility coefficient (D.C. = 13 %) and induced a very low retention of calcium in the body. EDTA-Na2 increased the efficacy of calcium absorption in presence of oxalate (16.5 %) but decreased the gained body calcium. The absorption efficacy of calcium given as a complex with EDTA-Na, (16.1 %) was smaller than the absorption obtained when calcium was given as a chloride (22.1 %). Digestibility coefficient of calcium given in the diet as carbonate (D.C. = 58.3 %) was higher than in the case when calcium was given as a complex with EDTA-Na2 (D.C. = 48.4 %). The nitril-triacetic acid caused a negative balance of calcium and a net loss of calcium in the bone. Protein quality had a strong influence; the calcium digestibility coefficient was higher in diets with peanut protein (D.C. = 58.3 %) than in those made with heated liver protein (D.C. = 35.3 %). Addition of lysine to the diet improved the calcium digestibility coefficient.