R. O. Maguire

Interaction of Calcium and Phytate in Broiler Diets. 1. Effects on Apparent Prececal Digestibility and Retention of Phosphorus

Phytate P utilization from soybean meal (SBM) included in broiler diets has been shown to be poor and highly dependent on dietary Ca intake. However, the effect of Ca on P utilization and on the optimal ratio of Ca to nonphytate P (Ca:NPP) when diets contained varying levels of phytate has not been clearly shown and was the objective of this research. A factorial treatment structure was used with 4 dietary Ca levels from 0.47 to 1.16% and 3 levels of phytate P (0.28, 0.24, and 0.10%). Varying dietary phytate P levels were obtained by utilizing SBM produced from 3 varieties of soybeans with different phytate P concentrations. Ross 508 broiler chicks were fed 1 of 12 diets from 16 to 21 d of age. Excreta were collected from 16 to 17 d and from 19 to 20 d of age and ileal digesta was collected at 21 d of age. Apparent prececal P digestibility decreased when dietary Ca concentration increased and was higher when diets contained low-phytate SBM. The apparent digestibility of Ca and percentage of phytate P hydrolysis at the distal ileum were not reduced when dietary phytate P concentration increased. Including low-phytate SBM in diets reduced total P output in the excreta by 49% compared with conventional SBM. The optimum ratio of Ca:NPP that resulted in the highest P retention and lowest P excretion was 2.53:1, 2.40:1, and 2.34:1 for diets with 0.28, 0.24, and 0.10% phytate P. These data suggested that increased dietary Ca reduced the extent of phytate P hydrolysis and P digestibility and that the optimum Ca:NPP ratio at which P retention was maximized was reduced when diets contained less phytate P.

Critical evaluation of the implementation of mitigation options for phosphorus from field to catchment scales.

Nutrient regulations have been developed over the past decades to limit anthropogenic inputs of phosphorus (P) to surface waters. All of the regulations were promulgated in response to decreased water quality, which was at least partially associated with agricultural non-point source pollution. Improvements in water quality can take years, so the impacts of these regulations on water quality can not always be seen. Denmark has had nutrient management regulations aimed at achieving mass balance of P for 20 yr, and although great progress has been made, an average surplus of 11 kg P ha(-1) remains. Northern Ireland is also trying to move toward mass balance, but decreases in inorganic P fertilizer use have been undermined by an increase in the use of feed concentrates. In the Chesapeake Bay watershed, which covers several states in the USA, a variety of best management practices are starting to have an effect on P losses from agriculture, but water quality has only improved slightly. Impairment to the supply of drinking water to the City of Tulsa Oklahoma led to a lawsuit that has greatly affected the management of poultry litter in the supplying watershed. This paper discusses the different regulations that have developed in these four regions, evaluates the strategies used to prevent non-point source pollution of P, reports impacts on water quality, and looks for lessons that can be learned as we move forward.

Evaluation of phosphorus characterization in broiler ileal digesta, manure, and litter samples: (31)P-NMR vs. HPLC.

Using 31-phosphorus nuclear magnetic resonance spectroscopy ((31)P-NMR) to characterize phosphorus (P) in animal manures and litter has become a popular technique in the area of nutrient management. To date, there has been no published work evaluating P quantification in manure/litter samples with (31)P-NMR compared to other accepted methods such as high performance liquid chromatography (HPLC). To evaluate the use of (31)P-NMR to quantify myo-inositol hexakisphosphate (phytate) in ileal digesta, manure, and litter from broilers, we compared results obtained from both (31)P-NMR and a more traditional HPLC method. The quantification of phytate in all samples was very consistent between the two methods, with linear regressions having slopes ranging from 0.94 to 1.07 and r(2) values of 0.84 to 0.98. We compared the concentration of total monoester P determined with (31)P-NMR with the total inositol P content determined with HPLC and found a strong linear relationship between the two measurements having slopes ranging from 0.91 to 1.08 and r(2) values of 0.73 to 0.95. This suggests that (31)P-NMR is a very reliable method for quantifying P compounds in manure/litter samples.

The Effect of Quicklime (CaO) on Litter Condition and Broiler Performance

High levels of phosphorus and pathogens in runoff are 2 major concerns following manure applications to fields. Phosphorus losses from fields following manure applications have been linked to the solubility of phosphorus in manure; therefore, by decreasing manure phosphorus solubility, a decrease in phosphorus loss in runoff should be apparent. The objective of this research was to develop a process using quicklime that would result in reduced phosphorus solubility and bacteria counts in broiler litter. The 4 litter treatments evaluated were T1, new wood shavings without the addition of quicklime; T2, used, untreated broiler litter; T3, used litter with 10% quicklime (based on the weight of the litter); and T4, used litter with 15% quicklime (based on the weight of the litter). Body weight, cumulative feed consumption, and feed conversion (feed:BW) were determined on a weekly basis through 42 d of age. Mortality was recorded daily. Carcass weights and percentages of carcass yield without giblets were determined prechill. Litter pH, total phosphorus, nitrogen, soluble phosphorus, litter moisture (%), and total plate counts were measured for each litter treatment on d 7 and 42 after bird placement. No significant differences were found for BW, feed consumption, feed conversion, mortality, carcass weight, or carcass yield. No breast or footpad blisters were observed. On d 7, 15% quicklime had higher (P < 0.001) pH (11.2) when compared with the other treatments. Percentages of phosphorus and nitrogen were lower (P < 0.001) for new wood shavings in comparison with the used litter treatments. Soluble phosphorus (ppm) was lower (P < 0.001) for 15% quicklime (2.75) when compared with new wood shavings (42.2), untreated broiler litter (439.2), and 10% quicklime (35.0). Although not significant, 15% quicklime had lower total plate counts (cfu/g) in comparison with the other treatments on d 1 and 10 postmixing and at 7 d after bird placement. Litter conditions on d 42 after bird placement were similar. We concluded that the use of quicklime as a treatment for broiler litter would initially reduce nitrogen and soluble phosphorus and bacteria counts without negatively affecting bird productivity.

Interaction of Calcium and Phytate in Broiler Diets. 2. Effects on Total and Soluble Phosphorus Excretion

Dietary Ca has been reported to influence the amount of phytate excreted from broilers and affect the solubility of P in excreta. To address the effects of dietary Ca and phytate on P excretion, 12 dietary treatments were fed to broilers from 16 to 21 d of age. Treatments consisted of 3 levels of phytate P (0.10, 0.24, and 0.28%) and 4 levels of Ca (0.47, 0.70, 0.93, and 1.16%) in a randomized complete block design. Feed phytate concentrations were varied by formulating diets with 3 different soybean meals (SBM): a low-phytate SBM, a commercial SBM, and a high phytate Prolina SBM having phytate P concentrations of 0.15 to 0.51%. Fresh excreta was collected from cages during 2 separate 24-h periods; collection I commenced after the start of dietary treatments (16 to 17 d) and collection II followed a 3-d adaptation period (19 to 20 d). Ileal samples were also collected at 21 d. Excreta samples were analyzed for total P, water soluble P (WSP), and phytate P, whereas ileal samples were analyzed for total P and phytate P. Results indicated that excreta total P could be reduced by up to 63% and WSP by up to 66% with dietary inclusion of low-phytate SBM. There was a significant effect of dietary Ca on both the excreta WSP and the ratio of WSP:total P. As dietary Ca increased, the excreta WSP and WSP:total P decreased, with the effects being more pronounced following a dietary adaptation period. There was a linear relationship between the slope of the response in WSP to dietary Ca and feed phytate content for excreta from collection II (r(2) = 0.99). There was also a negative correlation between excreta phytate concentration and excreta WSP during both excreta collections. The response in WSP to dietary manipulation was important from an environmental perspective because WSP in excreta has been related to potential for off-site P losses following land application.

Broiler breeder manure phosphorus forms are affected by diet, location, and period of accumulation

Phosphorus (P) modifications of poultry diets have successfully decreased the total P (TP) in manures, but the effects on manure water-soluble P (WSP(M)) remain unclear. Our objectives were to characterize P forms in broiler breeder manures as affected by dietary P modification, location within the pen, and manure accumulation period. Two diets were formulated with and without phytase to attain 0.40% available P (AvP) during the breeder laying phase (22-64 wk of age). Manure was collected after accumulation periods of 48 h, 3 wk, and 39 wk in locations under the feeder and drinker and under the common area (between the feeder and drinker) of the pen. The TP, WSP(M), orthophosphate, and phytate in manure were measured. Broiler breeders that were fed phytase with a simultaneous reduction in nonphytate P (NPP) produced manures with 15% lower TP than those fed a traditional diet, but did not change WSP(M) when averaged over manure accumulation periods and locations within the pen. Regardless of diet, location within the pen, or accumulation period (r(2) = 0.76), the WSP(M) increased linearly as the manure moisture increased. As manure accumulation periods increased (48 h, 3 wk, and 39 wk), TP manure concentrations increased (11.9, 13.2, and 17.3 g/kg, respectively), orthophosphate proportions increased (73.2, 80.1, and 91.0%, respectively), and phytate proportions decreased (23.1, 17.0, and 6.7%, respectively). The mineralization of phytate and other organic complexes, which drive off carbon dioxide, presumably contributed to the increased orthophosphate and TP concentrations. Keeping breeder manures dry helps to avoid the mineralization of phytate to orthophosphate; this mineralization increased WSP(M) in our study, and thus increased the potential for elevated P loss in runoff when surface applied.

Modifying broiler diets with phytase and vitamin D metabolite (25-OH D(3)): impact on phosphorus in litter, amended soils, and runoff.

Adding phytase and 25- hydroxycholecalciferol (25-OH D(3)) to broiler diets has been shown effective at reducing total P concentrations in broiler litter. This study was conducted to determine the impact of field application of broiler litter from modified diets on P solubility in litter-amended soils and P losses in runoff. Five broiler diets and their resulting litters were evaluated: a high P diet, a low P diet, each of those basal diets with phytase added, and a low P diet with phytase and 25-OH D(3) added. A field study was initiated at two sites with each of the five broiler litters and a commercial P fertilizer (triple superphosphate [TSP]) applied at the same total P rate (150 kg P ha(-1)) and a control where no P was applied. Soil P was monitored over time at two depths (0-5 cm and 0-15 cm) soils were collected in the spring and fall to perform rainfall simulation studies. Broiler litter or TSP application increased soil water-soluble P and Mehlich 3-P concentrations relative to the control, however there were no consistent differences detected between litter treatments. Results from the rainfall simulation experiments indicate that diet modification with phytase or 25-OH D(3) does not increase the potential for P losses in runoff from amended soils relative to traditional diets. Moreover, broiler diet modification to reduce excreted P could be a potentially effective method for reducing watershed scale P surpluses in areas of intensive broiler production, without raising concerns over soluble P losses from litter-amended soils.

Evaluating the Influence of Storage Time, Sample‐handling Method, and Filter Paper on the Measurement of Water‐Extractable Phosphorus in Animal Manures

Abstract Surface‐applied manures create a potential phosphorus (P) runoff hazard, especially when unincorporated. In such cases, the concentration of water‐extractable P in the manure has been correlated to soluble P concentrations in runoff. This study evaluated the influence of holding time, sample‐handling procedure, and filtration method on measurement of the water‐extractable P content of manures in a 3×3×2 factorial arrangement of treatments. A two‐way interaction between holding time and sample‐handling procedure occurred for most samples. Six samples had water‐extractable P concentrations that were less than or equal to dried and dried/ground treatments. Only one sample had higher water‐extractable P concentrations for fresh than for dried and dried/ground treatments. When significant differences occurred as a result of the filtration method, results for Whatman No. 40 filters, with a larger pore size than 0.45 µm nitrocellulose membranes, were usually higher. There was no significant difference in the coefficient of variation across sample‐handling procedures, suggesting that efforts to dry and/or grind samples were not needed. These results support the adoption of a standardized protocol for measuring water‐extractable P in manures that represents the appropriate balance between the ease of implementation and the strength of the correlation to P runoff concentrations.

Plant-Available Phosphorus after Application of Synthetic Chelating Agents

ABSTRACT Fertilizer phosphorus (P) can become immobilized in acidic soils through bonds with iron (Fe) and aluminum (Al). Two chelating agents, ethylenediamine tetraacetic acid disodium salt (EDTA) and hydroxyethyl ethylenediamine triacetic acid (HEEDTA), were tested in a greenhouse study for efficiency at increasing plant-available P to corn (Zea mays L.). Fertilizer P was added with or without chelate to the center of pots, simulating a starter band of P. Without the presence of chelates, biomass above and below ground increased linearly as P fertilizer rates increased at 0, 9.6, 19.3, 28.9, and 38.5 kg P ha−1. Applications of EDTA and HEEDTA did not significantly increase water-soluble P (WSP), Mehlich 1 P, and Mehlich 3 P compared to soils without chelates. Applications of EDTA increased P uptake in the belowground biomass. Despite previous research showing that chelates increased WSP in soils, a decrease in P sorption was not observed with the additions of chelating agents to soils.

Phytate Quantification using HPIC in the Presence of Iron and Aluminum

Phytate is an organic form of P that is difficult to analyze in complex matrices. To test 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), researchers spiked dairy manure and broiler litter samples with Al, Fe, and phytate. Samples were alkaline extracted, acidified, and filtered, and then phytate spike recovery was analyzed with HPIC. High concentrations of Fe did not hinder phytate recovery in manure or litter samples. While phytate recovery was complete 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 relatively accurate, fast, and cheap within normal Al and Fe ranges, compared to the commonly used nuclear magnetic resonance (NMR) method.