Phosphorus digestibility and phytate degradation by yearlings and mature horses.

This research looks into the capacity of young and mature horses to digest phosphorus, particularly in the form of phytate. The study suggests that both young and old horses can effectively digest organic phosphorus, negating the need for additional inorganic phosphorus in their diet.

Background

• The research starts with the issue of phosphorus supplementation for horses, where inorganic phosphorus is often incorporated in the diet of growing horses.
• The rationale behind this is the belief that horses digest organic phosphorus or phytate-phosphorus less efficiently. The study questions this belief, suggesting that if horses, regardless of age, can digest organic phosphorus effectively, this would reduce the need for supplementation with inorganic phosphorus.

Study Design

• The research was designed to specifically investigate this question. It involved four yearling geldings and four mature geldings which were fed a diet of alfalfa cubes, timothy cubes, and a pelleted concentrate.
• The diet was formulated to contain 0.28% total phosphorus, out of which 17.4% was in the form of phytate-phosphorus.
• The authors allowed a 14-day period for diet adaptation and then a 4-day fecal collection period. The apparent total tract phosphorus digestibility and phytate-phosphorus disappearance were then measured and compared between the yearlings and the mature geldings.

Results and Implications

• The results showed a higher apparent total tract phosphorus digestibility for yearlings than mature geldings. However, the disappearance of phytate-phosphorus did not significantly vary between the two age groups.
• In terms of calcium digestibility, it was found to be lower in mature geldings, while the digestibility of magnesium did not show a significant difference based on age.
• These findings suggest that phosphorus, particularly derived from the organic form or phytate form, is broken down in the gastrointestinal tract.
• However, low phosphorus digestibility implies that the liberation of phosphorus either happens after its absorption site or the liberated phosphorus is recycled back into the gastrointestinal tract.
• The study concludes that yearlings appear to utilize organic phosphorus as effectively as mature horses, suggesting that diets without the need for inorganic phosphorus supplementation can be suitable for growing horses.