Enviropig - Background and Development

Background and Development

Enviropigs produce the enzyme phytase in their salivary glands. When cereal grains are consumed, the phytase mixes with feed in the pig's mouth, and once swallowed the phytase is active in the acidic environment of the stomach degrading indigestible phytic acid with the release of phosphate that is readily digested by the pig.

Cereal grains including corn, soybean and barley contain 50 to 75% of their phosphorus in the form of phytic acid. Since the Enviropigs can now digest phytic acid, there is no need to include either a mineral phosphate supplement or commercially produced phytase to balance the diet. Because no phosphorus is added to the diet and there is digestion of the phytic acid, the manure is substantially reduced in phosphorus content, ranging from a 20 to 60% decrease depending upon the stage of growth and the diet consumed.

The Enviropig was developed by the introduction of a transgene construct composed of the promoter segment of the murine parotid secretory protein gene and the E. coli phytase gene. This construct was introduced into a fertilized embryo by pronuclear microinjection, and this embryo along with other embryos was surgically implanted into the reproductive tract of an estrous synchronized sow. After a 114 day gestation period, the sow farrowed and piglets born were checked for the presence of the transgene and for phytase enzyme activity in the saliva. Through breeding, this line of pigs is in the 10th generation, and the phytase trait is stably transmitted in a Mendelian fashion.

An editorial entitled "Genetically engineered meat close to your table" was published with online video and audio explaining the digestive capability of the Enviropig.