Influence of high phosphorus intake on salivary and plasma concentrations, and urinary phosphorus excretion in mature ponies.

The research paper investigates how a high phosphorus intake can influence the salivary and plasma concentrations, as well as urinary phosphorus excretion, in mature ponies. The experiment indicated that plasma phosphorus concentration was increased and urinary phosphorus excretion heightened during high phosphorus feeding periods, yet there was no significant effect on salivary phosphorus concentration.

Experimental Design

• The study followed an A-B-A experimental design, where six ponies were initially fed a high phosphorus (HP) diet (HP1).
• This was followed by a low phosphorus (LP) diet, and then a return to the high phosphorus diet (HP2). Each treatment period lasted 30 days.

Effects of High Phosphorous Intake

• The high phosphorus diet provided 21 g of phosphorus per day, leading to an increase in urinary phosphorus excretion that equaled roughly 7% of phosphorus intake. This was a significant increase compared to the 0.5% seen with the low phosphorus diet.
• A higher concentration of plasma phosphorus was observed for the high phosphorus treatment. However, the salivary phosphorus concentration remained unaffected, with results ranging between 0 to 1.01 mmol P/l across the ponies. The study thus proposes that salivary excretion is not a crucial route for phosphorus removal.

Impacts on Calcium and Magnesium Levels

• Both the high and low phosphorus diets provided around 21 g of calcium and 6 g of magnesium each day.
• Different phosphorus intake levels showed contrasting effects on urinary excretion of these minerals. The percentage of calcium and magnesium in urine was found to be significantly higher during the low phosphorus treatment compared to the high phosphorus treatments.
• Based on these results, the paper suggests a possible role of salivary magnesium in maintaining magnesium homeostasis.