Accurate quantification of phosphorus (P) fractions in manures and agricultural runoff is vital to understanding P dynamics in the environment. Phytate is an organic form of P, with 6 phosphate groups, which is found in manures, but is difficult to quantify due to its affinity for complex formation with aluminum (Al) and iron (Fe). The objective of the first study was to measure if high concentrations of aluminum (Al) and iron (Fe) hinder accurate quantification of phytate in dairy manure and broiler litter when measured by high performance ion chromatography (HPIC). In this study dairy manure and broiler litter samples were spiked with Al, Fe, and phytate. Samples were alkaline extracted, acidified,cleaned up and filtered, and then phytate was analyzed with HPIC. High concentrations of Fe did not hinder phytate recovery in manure or litter samples. While phytate recovery was close to 100% at typical manure and litter Al concentrations, high concentrations of Al inhibited phytate recovery in litter samples and in some manure samples. Overall, alkaline extraction of dairy manure and broiler litter and analysis with HPIC proved to be a relatively accurate, fast and cheap within normal Al and Fe ranges, compared to the commonly used NMR method. The developed method was then used to measure the concentration of phytate P (Pp) rather than the entire phytate molecule (6 moles Pp per mole phytate) in runoff waters and in an adsorption study. Phytate P has not been previously measured in runoff, due to the low concentrations of Pp found in runoff and the complexity Pp extraction from runoff. Runoff treatments were dairy manure with and without added Pp (DM, DM+Pp), broiler litter with and without added Pp (BL, BL+Pp), and control, with and without two levels of Pp (control, control Pp low, control Pp high). Runoff was collected under simulated rainfall and analyzed for total and dissolved reactive P (DRP). Runoff was also separated into sediment (>0.45"m) and liquid (<0.45"m and lyophilized) fractions for Pp analysis by high performance ion chromatography (HPIC). The new method for Pp analysis recovered 70% of Pp spiked into runoff samples. Phytate P was found only on the sediment fraction of runoff and was not detected in the liquid fraction, even when it was lyophilized and extracted. This agreed with the adsorption study, which showed strong adsorption of Pp. Phytate P loss from control Pp high was significantly greater than Pp loss from control. �When control Pp high was removed from analysis, Pp loss from BL, BL+Pp, DM, and DM+Pp was significantly greater than from control. Phytate P in the manures appeared to behave differently than pure Pp salts, likely to do the formation of protein-phytate and cation-phytate complexes in the manures. Phytate P had no effect on DRP in runoff for any treatment, indicating no significant release of inorganic P through competitive binding. The majority of P lost in runoff was in fractions other than DRP and Pp in the sediment fraction. Efforts to control the erosive loss of soil during rainfall events appear to be the best way to reduce total P loss, irrespective of the presence of Pp. / Master of Science

Successful implementation of dietary P management strategies demand improved understanding of P digestion dynamics in ruminants and this is not possible without a reliable and accurate phytate (Pp) quantification method. The objective of the first study was to develop a robust, accurate, and sensitive method to extract and quantify phytate in feeds, ruminant digesta and feces. Clean-up procedures were developed for acid and alkaline extracts of feed, ruminant digesta and feces and clarified extracts were analyzed for Pp using high performance ion chromatography (HPIC). The quantified Pp in acid and alkaline extracts was comparable for feed but alkaline extraction yielded greater estimates of Pp content for digesta and feces than did acid extraction. Extract clean-up procedures successfully removed sample matrix interferences making alkaline extraction compatible with HPIC. The developed method was applied to investigate the disappearance of Pp from the large intestine of dairy heifers. Eight ruminally- and ileally-cannulated crossbred dairy heifers were used and each heifer was infused ileally with 0, 5, 15, or 25 g/d Pp and total fecal collection was conducted. On average 15% of total Pp entering the large intestine was degraded but the amount of infused Pp did not influence the degradability of Pp. Net absorption of P from the large intestine was observed. A feeding trial was conducted to investigate the effect of dietary Pp supply on ruminal and post-ruminal Pp digestion. Six ruminally-and ileally-cannulated crossbred lactating cows were used and dietary treatments were low (0.10% Pp), medium (0.18% Pp), and high (0.29% Pp) Pp, and a high inorganic P (Pi; 0.11% Pp; same total P content as high Pp). Ruminal Pp digestibility increased linearly with dietary Pp. As in the infusion study, net disappearance of Pp from the large intestine was only 16% of total Pp entering the large intestine and not influenced by dietary Pp. Fecal P excretion increased linearly with increasing dietary Pp but was not affected by form of dietary P. In lactating cows Pp digestibility was not affected by dietary Pp and fecal P excretion was regulated by total dietary P rather than by form of dietary P. / Ph. D.