ABSTRACT: Fate of Microbial Phytase in the Gastrointestinal Tract of Chicks and Effects on Phosphorus Solubility

DWRC 2001 – 2002 Intern: Christina Eckstrand

Project Advisor: William Saylor

The broiler industry is a vital component of the agricultural enterprise in Delaware, producing approximately 260 million chickens per year, and generating in excess of one billion dollars for the State. As a result of the intensive animal density, however, a number of environmental concerns have been created, particularly in the environmentally-sensitive watersheds of the inland bays. The most pressing issue for the industry is the high concentrations of phosphorus (P) in soils created by years of land application of P-rich broiler litter, and the potential movement of that P into surface and ground waters. The high P concentrations in broiler excreta and hence litter is caused by the inefficient utilization of phytic acid P in the grain-based diets fed to broilers (and other non-ruminant animals). However, the advent of new technologies, including the feeding of microbially-derived phytase enzymes and low-phytate grains, reductions in the total amount of P that must be fed to broilers to meet their nutritional requirements are being realized.

Objectives

The use of phytase in the diet shows significant promise for improving P utilization in chickens. One concern that has been raised, and requires study, is the fate of these phytase enzymes in the gastrointestinal (GI) tract of chickens and whether any meaningful quantities are excreted into the environment. This objectives of this study are:

1. To investigate how much active phytase is excreted by phytase-fed chickens
2. To investigate the impact of excreted active phytase on litter and soil P.

It has been suggested that phytase entering the environment might continue to hydrolyze organic P in the litter and soil, and by increasing the concentration of soluble P, promote the movement of litter and soil P into surface and ground waters. The study investigates the fate of microbial phytase provided in the diet of broiler chicks through the length of the GI tract, and in the excreta.

One-day-old broiler chicks were fed diets containing graded level of microbial phytase together with graded levels of non-phytate P (nPP) for periods of one, two, three, and four weeks. Excreta samples were collected from each pen on a weekly basis for phytase activity and total and soluble P. At the end of each period, chicks were euthanized and the gastrointestinal tract including the proventriculus, gizzard, duodenum, ileum, and cecum, were removed. The gut contents were collected from each gut section and immediately placed in liquid nitrogen to prevent loss of enzyme activity. All samples were analyzed for phytase activity, total, soluble, and phytate P. Phytase activity, and total, soluble and phytate P concentrations in all diets were determined as well.