Effects of high calcium intake on fat digestion and bile acid excretion in feces of veal calves.

We tested the hypothesis that apparent digestibility of fat by veal calves is determined by the participation of bile acids in the process of fat absorption and is, therefore, negatively associated with bile acid excretion in feces. Veal calves were fed milk replacers that contained whey protein and either a low (5.2 g of calcium/kg of air-dried diet) or high (12.4 g of calcium/kg of air-dried diet) concentration of calcium. The high calcium milk replacer contained extra calcium in the form of calcium formate. Final body weight was not significantly influenced by diet after the milk replacers had been fed for 27 wk. Feces were quantitatively collected during wk 23 of the trial. The high calcium milk replacer reduced apparent fat digestibility by 5.6 percentage units and increased bile acid excretion in feces by 90% compared with the low calcium milk replacer. The extra calcium intake decreased apparent absorption of magnesium and phosphorus. We proposed that a high intake of calcium by veal calves would increase the amount of insoluble calcium, magnesium, and phosphate complexes in the intestinal lumen, which, because of the binding of bile acids, would exclude bile acids from the process of fat digestion and inhibit reabsorption of bile acids. As a result, fat digestion is impaired, and bile acid excretion in feces is enhanced. The complex formation in the ileal lumen also explains why high calcium intake reduces magnesium and phosphorus absorption in veal calves.