Inhibition of calcium absorption in ponies fed diets containing oxalic acid.

The study tested the impact of oxalic acid on calcium absorption in Shetland ponies and found that oxalic acid increased their calcium excretion and decreased absorption, negatively affecting their calcium balance.

Objective of the Study

• The research sought to investigate the role of dietary oxalic acid in influencing calcium absorption, excretion, and retention in Shetland ponies. The effects were analyzed through two separate experiments where the control diet was compared against a diet laced with 1% oxalic acid.

Experimental Design

• In the first experiment, the researchers fed the ponies a control diet of oats, molasses, and a complete pelleted horse ration with 0.6% calcium. This was then compared against the results obtained from feeding the horses the same diet but with a 1% oxalic acid addition.
• In the second experiment, the calcium content was reduced to 0.45% while maintaining the presence of oxalic acid in one of the diets.

Study Findings

• The addition of oxalic acid resulted in a higher fecal excretion of calcium and decreased levels of calcium absorption in the ponies.
• The study noted that the dietary oxalic acid did not affect the endogenous fecal excretion of calcium, suggesting that the increase in fecal calcium was due to unabsorbed dietary calcium.
• Ponies on diets containing 1% oxalic acid and 0.45% calcium ended up having a negative calcium balance.
• Contrary to expectations, the ponies did not conserve calcium by reducing urinary excretion when they were fed with oxalic acid.

Additional Findings

• The study also made observations on the magnesium balance in the three ponies using the first experimental design.
• Intake of oxalic acid resulted in an increased urinary excretion of magnesium and decreased magnesium retention in the ponies.

Conclusion

• The research concludes that dietary oxalic acid has a substantial negative effect on calcium absorption and retention in ponies, leading to conditions of negative calcium balance. Moreover, oxalic acid intake also alters magnesium balance in these animals.