Diet Composition and Mineral Balance in Guinea Pigs

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Abstract
Guinea pigs near maturity were used to study the effect of type of bulk, and of dietary levels of potassium, magnesium and phosphorus on apparent absorption and retention of calcium, magnesium, potassium, sodium and phosphorus. The most significant observation was that high dietary levels of phosphorus caused a negative balance of magnesium in guinea pigs that received about 0.1% of magnesium in the diet. The low retention was primarily due to the decreased absorption of magnesium in the presence of excess phosphorus regardless of the magnesium level. A similar though less marked effect was observed on the absorption and retention of potassium and calcium. Gum arabic was found to be highly digestible whereas celluflour was essentially indigestible. The absorption of all cations was about 10 percentage points higher from diets that contained gum arabic than from those that contained celluflour. Guinea pigs absorbed approximately 70% of the calcium and 90% of the magnesium consumed when they were fed a purified diet that contained 0.9% of calcium, 0.3% of magnesium and 0.4% of phosphorus. Large portions of the excreted calcium and magnesium, 62 and 87% respectively, were eliminated by way of the kidneys.