Calcium metabolism in ponies fed a high phosphorus diet.

The study investigates how a high phosphorous diet affects the way calcuim is metabolized in young Shetland ponies.

Research Methodology

• The study used metabolic balance and kinetic methods to examine calcium metabolism in four young Shetland ponies. These methods allow researchers to measure the amount of calcium absorbed and excreted by the body, as well as how it is distributed and used.
• The ponies were given a diet of 0.4% calcium and either 0.2% or 1.2% phosphorus, following a 2 × 2 Latin square experimental design, which is a method of experimental design that ensures a balanced comparison of the effects of different levels of phosphorus.

Findings

• The ponies showed a greater retention and plasma concentration of phosphorus when given the high phosphorus diet. This indicates that the body was retaining more of the phosphorus it consumed, a common sign of phosphorus deficiency.
• High intake of phosphorous was found to decrease calcium absorption, urinary excretion and retention, and it increased the total and endogenous calcium excreted via feces.
• Despite these changes, the ponies remained in positive calcium balance when fed either the baseline or high phosphorus diet, suggesting that they were still able to absorb and utilize sufficient amounts of calcium to maintain overall health.
• In three out of four ponies, the turnover of the bone (determined by the rate of calcium deposition in the skeleton and removal of calcium from the skeleton) was found to be increased with the high phosphate diet.
• On being fed the high phosphorous diet, the plasma calcium concentration was found to decrease. However, it was noted that increased turnover of bone calcium did not correspond to consistent changes in the exchangeable calcium pool, compartments of this pool or the rates of exchange.

Implication

• This research suggests that, at least in young Shetland ponies, it is possible to manage the intake of phosphorous without severely disrupting calcium metabolism, as long as the diet overall is balanced and provides sufficient calcium. However, excessive phosphorous intake could potentially disturb bone health, due to its impact on the turnover of bone, and so needs to be managed with care.