The effects of phytase and phytic acid on the loss of endogenous amino acids and minerals from broiler chickens

Abstract

1. The effects of myo-inositol hexaphosphate (IP₆) and phytase (EC 3.1.3.26) on the excretion of endogenous compounds were investigated using growing broiler chickens.

2. A total of 32 female Ross broilers were used in a precision feeding assay involving a 2×2 factorial arrangement of treatments. The materials administered were glucose, glucose + 1000 units of phytase activity (FTU), glucose + 1 g of IP₆ and glucose + 1 g of IP₆ + 1000 FTU. Excreta were collected quantitatively over a 48-h period following intubation of the test materials. The excretion of nitrogen, amino acids, minerals, sialic acid and phytate phosphorus was determined.

3. The ingestion of 1 g of IP₆ by broilers increased the excretion of endogenous nitrogen, amino acids, iron, sodium, sulphur and sialic acid compared with birds fed on glucose. Supplementation of IP₆ with exogenous phytase reduced the excretion of endogenous amino acids, calcium, sodium, phytate phosphorus and sialic acid compared with birds fed IP₆.

4. It can be concluded that IP₆ increases the excretion of endogenous minerals and amino acids in broiler chickens. Part of the beneficial effects of the addition of exogenous phytases to the diets of poultry appears to be mediated through a reduction in endogenous losses of these nutrients.

Acknowledgements

The Scottish Agricultural College receives funding from the Scottish Executive Environmental and Rural Affairs Department. Zymetrics Inc. provided financial support for the work. The statistical advice of Mr Ian Nevison, Biomathematics and Statistics Scotland, is gratefully acknowledged.