Effect of dietary phytate and phytase on proteolytic digestion and growth regulation of broilers

Abstract

This study was designed to investigate the effect of dietary phytate and phytase on proteolytic digestion and growth signalling in the gastrointestinal tract of broilers. Diets containing phytate phosphorus (2.2 or 4.4 g/kg) with phytase dose rates of 0, 500, or 1,000 FTU/kg were fed to 504 female Cobb chicks for three weeks. Diets containing high phytate reduced the activity of pepsin and trypsin, whereas the inclusion of microbial phytase increased the activity of pepsin, H⁺K⁺-ATPase, trypsin and alanyl aminopeptidase. In the intestine, phytate upregulated the mRNA expression of somatostatin, and down-regulated the mRNA expressions of ghrelin and target of rapamycin (TOR). Phytase down regulated the somatostatin gene, and upregulated the genes of ghrelin, TOR, p70 S6 kinase (S6K) and methionyl aminopeptidase. Significant interactions between phytate and phytase on the mRNA expressions of ghrelin, somatostatin and S6K in the jejunum were detected. The results suggest that dietary phytate and phytase can influence the gastrointestinal endocrine and exocrine systems, as well as the peripherally regulatory network of growth in broilers.

Keywords:

• broiler
• growth signalling
• phytic acid
• phytase
• proteinases

Acknowledgements

The authors are grateful to Dr A.J. Cowieson at AB Vista Feed Ingredients (Wiltshire, UK) for his constructive suggestions on the revision of this manuscript. The authors also are grateful to the staff of the Animal Biochemistry Laboratory of Henan University of Science and Technology (Luoyang, China) and the Poultry Nutrition Laboratory of Henan Agricultural University (Zhengzhou, China) for providing the experimental facilities and carrying out most of the practical work for this experiment.