Author
|
Submitted to: ASA-CSSA-SSSA Proceedings
Publication Type: Proceedings Publication Acceptance Date: 7/1/2005 Publication Date: 11/7/2005 Citation: Smith, D.R., Moore Jr, P.A. 2005. Potential impacts of phytase in swine diets on air, water and soil quality. In: Proceedings of the ASA-CSSA-SSSA Annual Meeting Abstracts, November 6-10, 2005, Salt Lake City, UT. 2005 CDROM. Interpretive Summary: Adding phytase to animal diets can reduce phosphorus (P) losses from manures. However, the full environmental impacts of dietary modification treatments are not fully understood. A study was conducted in which nursery swine were fed a commercial diet, or a phytase diet. Ammonia volatilization and manure chemistry were monitored during the 6-week feeding trials. Manure was applied to plots and runoff from simulated rainfall was characterized. In a final study with manure from the feeding trials, manure was added to high and low soil test phosphorus soil, and changes in soil test phosphorus fractions were characterized during a 16-week incubation period. Ammonia volatilization was reduced by 26% from phytase fed animals compared to animals fed the normal diet. Manure soluble P was reduced by 17% with inclusion of phytase in the diet, however there was a 25% increase in soluble P runoff from the phytase manure compared to the normal diet manure. Soluble P was roughly equal for normal and phytase manure immediately following addition of manure to high STP soil. However, there was 13% more soluble P in phytase manure 2 weeks following application, and 25% increase in soluble P 16 weeks after application. Phytase may induce important production and environmental benefits through reduction in NH3 losses, however water quality benefits may not be immediately realized. The impact of this research is to provide information to other scientists, policy makers and producers about how phytase added to swine manure can affect air, water and soil quality. Technical Abstract: Dietary modification with phytase is one strategy to reduce P inputs into animals, and thus P losses from manures. However, the full environmental impacts of dietary modification treatments are not fully understood. A study was conducted in which nursery swine were fed a commercial diet, or a phytase diet. Ammonia (NH3) volatilization and manure chemistry were monitored during the 6-week feeding trials. Manure was applied to plots and runoff from simulated rainfall was characterized. In a final study with manure from the feeding trials, manure was added to high and low soil test P (STP) soil, and changes in STP fractions were characterized during a 16-week incubation period. Ammonia volatilization was reduced from 109 mg NH3/m2/h from manure in pens of swine fed the normal diet to 81 mg NH3/m2/h from phytase diet manure, a 26% reduction. Manure soluble P was reduced by 17% with inclusion of phytase in the diet, however there was a 25% increase (not significant) in soluble P runoff from the phytase manure compared to the normal diet manure. Soluble P was roughly equal for normal and phytase manure immediately following addition of manure to high STP soil. However, there was 13% more soluble P in phytase manure 2 weeks following application, and 25% increase in soluble P 16 weeks after application. Phytase may induce important production and environmental benefits through reduction in NH3 losses, however water quality benefits may not be immediately realized. |
