Use of Endogenous Vertebrate Phytase to Increase Capacity To Utilize Phytic Acid in Livestock Feed
Description of Invention:
This invention discloses the concept of creating transgenic farm animals that secrete a native phytase enzyme into their digestive tracts. It has long been recognized that monogastric animals (e.g. pigs and chickens) do not utilize dietary phosphorus as efficiently as possible. This is because a high percentage of total phosphorus (70% in cereals, 50% in legume seeds) is present as phytic acid and its salts - phytate. Monogastric animals utilize phytate inefficiently because they lack the enzyme phytase in their digestive systems. Phytase liberates the phosphorus from phytate, thereby making dietary phosphorus available to the animals. This has the dual effect of both promoting more efficient growth of the animals, as well as imposing less of an environmental burden in the form of excess phosphorus in water streams.
Use of phytase as a growth feed supplement is well known. However, in the past the focus has always been on adding exogenous phytase to animal feed, or to increase the level of phytase expression in the seeds making up the feed. The inventors' novel concept is to redirect expression of a naturally occurring phytase gene so that the enzyme will be secreted into the intestinal lumen. This will create farm animals that can more efficiently utilize unsupplemented feeds. Another problem with existing phytases that the present invention overcomes is that phytase tends to be unstable during the heat treatment used to process feed. This invention overcomes this limitation because the phytase does not have to be incorporated into feed at all.
