Phytase Use to Reduce Phosphorous Content in Manure

January-March 2002

Dennis DeWitt , livestock specialist


Current manure nutrient management plans use Nitrogen (N) as the deciding factor to determine gallons/per acre. Laws are being written to change to a phosphorus (P) based comprehensive nutrient management plan. For some livestock operations, soil P levels will potentially increase number of acres needed for manure application. Phytase, an enzyme that breaks down the indigestible phytic acid (phytate) portion in grains and oil seeds, releases digestible phosphorus for the pig.

Furthermore, the essential nutrients previously bound to the phytate P lose their binding site and are capable of being absorbed by the digestive tract. Studies at Iowa State University and elsewhere have documented that the inclusion of phytase in swine diets has increased the availability of phytate phosphorus in corn-soybean meal diet from approximately 15-45%. As a general rule, the amount of P reduction in the diet will cause a similar phosphorus reduction in the manure. For years the addition of phytase to swine rations was economically not practical. Recently, competition between companies has made commercial phytase practical. However, producers do not realize there is no impact on cost of production.

Response :

Palmer Holden, Dave Stender, Jerry Weiss and Dennis DeWitt organized 12 Pork Producer's roundtable discussion groups for sharing of this production technology. The discussion agenda was:

1) How phytase works and why it may be advantageous to use

2) Phytase management including proper ration balancing, storage and ration levels; and

3) Implementation of phytase and cost analysis


Twenty-three out of 34 pork producer evaluations were turned in and tabulated. The weighted mean of knowledge before meeting on how and why phytase works; phytase management including ration balance, storage and use; and cost analysis and implementation of phytase was 2 (1-low, 5-high) and knowledge rate after meeting weighted mean was 4. Two producers are already using phytase and 11 more said they are very likely to use phytase. Only one producer said he will not be using phytase. He has to add P to his cropland, so there is no need to reduce it in the manure. The total increase in income level from knowledge gained from this series of meetings is $45,600!


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