Pigs expressing salivary phytase produce low-phosphorus manure

To address the problem of manure-based environmental pollution in the pork industry, we have developed the phytase transgenic pig. The saliva of these pigs contains the enzyme phytase, which allows the pigs to digest the phos phorus in phytate, the most abundant source of phosphorus in the pig diet. Without this enzyme, phytate phosphorus passes undigested into manure to be come the single most important manure pollutant of pork production. We show here that salivary phytase provides essentially complete digestion of diet ary phytate phosphorus, relieves the requirement for inorganic phosphate su pplements, and reduces fecal phosphorus output by up to 75%. These pigs off er a unique biological approach to the management of phosphorus nutrition a nd environmental pollution in the pork industry.