Effect of Phytase Supplementation On Protein Digestibility in Horses At Maintenance
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Protein digestibility in horses has been researched for years. Despite established requirements, the feeding of too much protein has become a major environmental concern for its role in excess nitrogen emissions. Recent studies have looked to improve protein digestibility in horses so as to reduce the amount of nitrogen released into the environment. The enzyme phytase has been extensively studied for its effects on improving the digestibility of phosphorus, but little has been done to observe its effects on protein digestibility. Phytate, the form in which plant phosphorus is found, has been observed developing complexes with amino acids and proteins. Because phytase has been found to improve the digestibility of phosphorous in this form, it could also improve protein availability. Six mature Arabian geldings were used in a 6 x 6 Latin square design to study protein digestibility during phytase supplementation. Horses were fed one of six rotating diets for a I4-day period. Each I4-day period consisted of an II-day adaptation period followed by a 3-day total collection. Throughout the study, each horse received all six diets without repeating. Body weights for each horse declined over the duration of the study resulting in a decrease in the amount of concentrate, hay, and nitrogen consumed each day. Nitrogen content of both feces and urine did not differ by diet nor did nitrogen output. Apparent nitrogen digestibility did vary by diet. This, however, was only due to the large hay content of diets five and six. No affect of phytase supplementation on protein digestibility in horses was found, as there was no illustrated effect on apparent digestibility by the addition of phytase into the horses' diets.