Calcium Utilization and Feed Efficiency in the Growing Rat as Affected by Dietary Calcium, Buffering Capacity, Lactose and EDTA

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Abstract
An experiment was designed to study the relationships of calcium, buffering capacity (BC), lactose and ethylendiaminetetraacetic acid (EDTA) in the nutrition of the growing rat. For the replicated, factorially arranged experiment, which involved calcium (0.19, 0.48 and 0.78%), buffering capacity (BC 1, 0.46, BC 2, 0.54 and BC 3, 0.76 ml of 1 N HCl required to reduce the pH of 5.0 g of the diet by one pH unit), lactose (0 and 12%), and EDTA (0 and 0.2%), 152 rats were used. Dihydrogen-to-monohydrogen phosphate ratios were varied to produce the different BC's, and a constant phosphorus (0.4%) was provided for all diets. As dietary calcium increased from 0.19 to 0.48%, retention and deposition of calcium in the total body and in the femur and efficiency of feed conversion showed improvement. However, 0.78% calcium did not prove beneficial over 0.48% calcium. The diets which produced the most acidic condition (BC 1) in the stomach, resulted in the most improved calcium retention, feed intake and efficiency of feed conversion. As judged from the reduced fecal calcium with BC 1 diets, the calculated increase in urinary calcium was not great enough to offset the increased calcium absorption in the intestine. Lactose increased calcium retention and improved bone calcification, and, for the total 6-week experimental period, EDTA decreased the retention and deposition of calcium.