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United States Department of Agriculture

Agricultural Research Service

Title: PHOSPHORUS COMPOSITION OF MANURE FROM SWINE FED LOW-PHYTATE GRAINS: EVIDENCE FOR HYDROLYSIS IN THE ANIMAL

Authors
item Leytem, April
item Turner, Benjamin - UNIVERSITY OF FLORIDA
item Thacker, P - UNIV. OF SASKATCHEWAN

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2004
Publication Date: November 30, 2004
Citation: Leytem, A.B., Turner, B.L. 2004. Effect of feeding low phytate barleys on manure phosphorus forms in swine. Journal of Environmental Quality. 33:380-2383.

Interpretive Summary: Feeding low phytate grains to monogastric animals, such as swine, can enhance phosphorus (P) uptake and reduce the total amount of P excreted. By reducing the total P in manures, problems associated with soil P loading in areas of concentrated animal production can be somewhat alleviated. One concern that has been expressed is that changing the manure composition may enhance the P solubility of the manures, creating an environmental risk. We investigated the effect of feeding four low phytate barley based diets to swine on manure P composition. Total C and N in the manures were similar, but total P concentrations ranged between 6.8 and 14.9 g P per kg, with concentrations in manures from animals fed the low phytate barleys being 25 to 54% lower than those fed the wild-type. Despite constituting up to 30% of the total P in feed, phytic acid concentrations determined by solution Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy were <10% of the total P in all manures, with inorganic orthophosphate constituting the major P fraction (70-81% of total P). This demonstrates that phytic acid is hydrolyzed in swine, even though the animals derive no nutritional benefit. Further, dietary manipulation had little effect on P forms in swine manure, so this is unlikely to influence the fate of P in the environment through changes in P composition.

Technical Abstract: Swine diets with low phytic acid grains can reduce manure P concentrations and soil P loading in areas of concentrated production. We investigated the effect of feeding these low phytic acid mutant grains on manure P composition, because this could influence the fate of P in the environment. Manure was collected from swine fed one of five barley-based diets containing varieties with different concentrations of phytic acid (myo-inositol hexakisphosphate). Total C and N in the manures were similar, but total P concentrations ranged between 6.8 and 14.9 g P per kg, with concentrations in manures from animals fed the mutant barleys being 25 to 54% lower than those fed the wild-type. Despite constituting up to 30% of the total P in feed, phytic acid concentrations determined by solution Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy were <10% of the total P in all manures, with inorganic orthophosphate constituting the major P fraction (70-81% of total P). This demonstrates that phytic acid is hydrolyzed in swine, even though the animals derive no nutritional benefit. Further, dietary manipulation had little effect on P forms in swine manure, so this is unlikely to influence the fate of P in the environment through changes in P composition. However, it is possible that changes in other manure properties may influence the behavior of P in soils.

Last Modified: 10/31/2014
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