Richard Wolfe
CS427
Abstract
April 22,2011
EnviroPig
The main concern of agriculture is to increase food production without degrading the
environment. Monogastric (single stomach) animals such as pigs and chickens are not able to digest
phytate and therefore produce manure that is high in phosphorus. Phosphorus is supplemented to the
diet of a pig in order to enhance growth. If the pig was able to extract the phosphorus that is found in
phytate, which is found naturally in their feed, then the supplement would not be necessary and the
phosphorus from the phytate would not be passed into their manure. Run off from using manure as
fertilizer adds excess phosphorus into streams and rivers disrupting the ecosystem. Phytase is an
enzyme that is found in E.coli that releases phosphorus from phytate. Previous studies used transgenic
mice to deliver E.coli phytase into the digestive tract through salivary glands. Transgenic pigs have
been developed that use this same concept. Pigs that produce salivary phytase require no supplement
and excrete 75% less phosphorus. A PSP/APPA transgene (parotid secretary protein promoter linked to
the E.coli appA phytase gene) was microinjected into 4,147 embryos and 33 transgenic founder pigs
were produced. The transgenic pigs were identified using PCR on DNA extracted from blood and tail
samples. When transgenic pigs were fed the same diet as non-transgenic pigs, the transgenic pigs
digested close to 100% of the phosphorus while the non-transenic pigs digested only 51%. Also, the
phosphate in the manure was reduced by up to 75% in the transgenic pigs. And almost all of the dietary
phosphorus was digested and absorbed. In a second test, the growth rate of the transgenic pigs was
slightly faster than non-transgenic pigs being fed a phosphorus supplement. Tissue samples were
analyzed and high phytase activity was detected only in parotid, sublingual, and submaxillary salivary
glands and low activity was found in the stomach and duodenal tissues. No activity was found in other
transgenic tissues. A western blot confirmed these results. This article shows that salivary phytase
enables digestion of phytate phosphorus and no phosphorus is required. Also, the phosphorus in
transgenic manure is reduced up to 75%. Finally, they have not detected any deleterious effect on
health or performance in the transgenic pig.
References:
1. Golovan SP,.....; Pigs expressing salivary phytase produce low-phosphorus manure. Nature.
August 2001, 741-745.