The percentage of feedlot feces and manure P that is water soluble was 41% (not accounting for additional soluble P from urine) and 24% respectively. The interaction of feces and urine with minerals and metals reduced the water solubility of P in feedlot manure relative to feces. Increasing dietary P level increased manure P concentration and water solubility of manure. Manure P from cattle fed feedlot diets containing 0.30% to 0.50% P was 28% water soluble P. The water solubility of P in feedlot feces and manure is an indicator of the potential for P runoff from feedlots and fields receiving manure

Bremer, Virgil R.

Buckner, Crystal D.

Erickson, Galen E.

Klopfenstein, Terry J.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department January 2008 Total and Water Soluble Phosphorus Content of Feedlot Cattle Feces and Manure Virgil R. Bremer University of Nebraska-Lincoln, vbremer2@unl.edu Crystal D. Buckner University of Nebraska-Lincoln, cbuckner2@unl.edu Galen E. Erickson University of Nebraska-Lincoln, gerickson4@unl.edu Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Bremer, Virgil R.; Buckner, Crystal D.; Erickson, Galen E.; and Klopfenstein, Terry J., "Total and Water Soluble Phosphorus Content of Feedlot Cattle Feces and Manure" (2008). Nebraska Beef Cattle Reports. 27. https://digitalcommons.unl.edu/animalscinbcr/27 This Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. © The Board of Regents of the University of Nebraska.  All rights reserved. 2008 Nebraska Beef Report  — Page 69 Total and Water Soluble Phosphorus Content of Feedlot Cattle Feces and ManureVirgil R. BremerCrystal D. BucknerGalen E. EricksonTerry J. Klopfenstein1SummaryThe percentage of feedlot feces and manure P that is water soluble was 41% (not accounting for additional soluble P from urine) and 24% respectively. The interaction of feces and urine with minerals and metals reduced the water solubility of P in feedlot manure rela-tive to feces. Increasing dietary P level increased manure P concentration and water solubility of manure. Manure P from cattle fed feedlot diets containing 0.30% to 0.50% P was 28% water solu-ble P. The water solubility of P in feedlot feces and manure is an indicator of the potential for P runoff from feedlots and fields receiving manure. IntroductionOf the P fed 80% to 88% is excreted in feces and urine by feedlot cattle. As dietary P intake increases, the form of P in runoff from fields receiving manure is impacted and may contribute to eutrophication. Water solubility of P may affect the runoff potential of P in compost applied to crop fields (2003 Nebraska Beef Report, pp. 52-54). However, no research has been conducted on the water solubility of P in feedlot feces and manure. Furthermore, the differ-ences in rate changes of soluble P to total P in feedlot manure and feces are unknown. The objective of our study was to evaluate the effect of dietary P on fecal and manure total P as well as water solubility of P in feces and manure of feedlot cattle.ProcedureTwo hundred fifty-four fecal sam-ples and 158 manure samples from 15 University of Nebraska–Lincoln feedlot cattle trials (1998 Nebraska Beef Report, pp. 77-80; 1998 Nebraska Beef Report, pp. 84-85; 1999 Nebraska Beef Report, pp. 60-62; 2000 Nebraska Beef Report, pp. 65-67; 2002 Nebraska Beef Report, pp. 45-48; 2002 Nebraska Beef Report, pp. 52-5; 2002 Nebraska Beef Report, pp. 54-57; 2003 Nebraska Beef Report, pp. 54-58; 2004 Nebraska Beef Report, pp. 49-51; 2004 Nebraska Beef Report, pp. 61-6; 2005 Nebraska Beef Report, pp. 51-5; 2005 Nebraska Beef Report, pp. 54-56) representing 1,608 cattle were analyzed for total P (TP) and water extractable P (WEP). Samples were from cattle fed diets containing 0.10% to 0.49% P. The cattle were consuming 20 to 57 g P and excreting 15 to 47 g P daily. Fecal samples (feces collected directly from steers) were collected from mass-balance pen studies, individually fed animals, and from metabolism ex-periments. Multiple samples were taken for each experimental unit over time and frozen. The fecal samples from the mass-balance studies were freeze dried, and the other fecal samples were oven dried at 60oC for 48 hours. All fecal samples were composited by experi-mental unit within each experiment for laboratory analysis.All manure samples (feces and urine mixed with soil over a feeding period) were collected from cattle fed in pens containing 8 to 11 steers at the University of Nebraska Mead Research Feedlot. In each study, manure was collected at the comple-tion of the feeding period. As the manure was removed from each pen, approximately 20 samples were col-lected, frozen, freeze-dried, ground, and composited by pen within trial. Total P (TP) of each sample was analyzed in duplicate by ashing 1 g of sample at 600oC for 6 hours, refluxing with 10 mL of  N HCl for 5 minutes, standardizing to 100 mL volume with double distilled water and filtering through filter paper (Whatman 42; 2.5 um). Water extractable P (WEP), the amount of P in a sample that is read-ily soluble in water, was analyzed in duplicate by shaking 0.5 g DM of each sample with 100 mL double distilled water at 150 rpm for 1 hour, a 50 mL aliquot was then centrifuged at 1,500 g for 10 minutes, 125 uL of concentrated HCl was added to a subsequent 14 mL aliquot of supernatant. All samples were stored at 4oC prior to colorimetric analysis with the molybdovanadate method on a spectrophotometer cali-brated with standards developed in a matrix similar to each analytical pro-cedure. Internal standards and blanks were included with each set of six samples for quality control.The ratio of WEP:TP will be used as an index of the potential of P in a sam-ple to be lost in runoff. An increase in WEP:TP means that the P in a sample is more likely to be lost in runoff than P from a sample that has a lower WEP:TP. The fecal and the manure samples were analyzed independently. An iterative meta analysis methodology was utilized to integrate quantitative findings from multiple studies using the PROC MIXED procedure of SAS. ResultsThe average, minimum, and maxi-mum TP, WEP:TP, and % ash values for fecal and manure samples are pre-sented in Table 1. Table 1. Average, minimum, and maximum P and ash values for feces and manure samples analyzed in this studya,b.  Average Minimum MaximumFeces Diet TP, % 0.29 0.10 0.49 TP, % 0.49 0.18 1.4 WEP:TP  0.41 0.20 0.80 Ash, % 12 4 0 Manure Diet TP, % 0. 0.18 0.49  Diet TP, g/day 6 21 57 TP, % 0.7 0.21 0.64 WEP:TP 0.24 0.12 0.47 Ash, % 7 48 89aTP = total phosphorus, WEP = water extract-able phosphorusbAll values are on a DM basis.(Continued on next page)Page 70 — 2008 Nebraska Beef Report  © The Board of Regents of the University of Nebraska.  All rights reserved.As proportionally more P was fed in feedlot diets, there was a quadratic response in the concentration of manure TP (Figure 1). Fecal WEP:TP increased linearly as diet P increased. Fecal P averaged 0.41 WEP:TP; how-ever, this average does not account for additional urinary soluble P contribu-tion. Cattle fed diets containing the highest concentration of P also pro-duced manure with the highest con-centration of TP. Increasing manure TP concentration resulted in a linear increase in manure WEP:TP (Figure 2). However, the increase was small. Increasing manure TP from 0.20% to 0.60% TP (diets containing 0.18% to 0.49% P) resulted in an 11 unit increase in WEP:TP.In one trial, 0.5% and 0.70% Ca diets were individually fed to cattle. Feeding 0.70% dietary Ca reduced fecal WEP:TP from 0.60 to 0.48 (18% reduction). All other samples in this study were from cattle consuming diets containing 0.65% to 0.70% Ca. Fecal samples contained a higher concentration of TP than manure samples, even though the fecal sam-ples were collected from cattle fed diets containing less P than diets fed to cattle that manure samples were collected from. Diet TP, soil contami-nation, P loss in runoff and degree of OM loss (bacterial breakdown to CO2) may affect TP concentration of manure. Increased soil contamination and manure P loss in runoff would be expected to decrease the concentra-tion of TP in manure relative to feces. The net effect of decreased manure TP relative to feces was presumably caused primarily by soil contamina-tion to feces and urine on the pen surface. The WEP:TP of manure was less than the WEP:TP of feces, regardless of dietary P level (Table 1). This may be due to interaction of excreted P with minerals and soil metals. The interaction of Ca with P has been shown to decrease the WEP:TP of feces. Previous research has shown excreted P can interact with Ca, Al, and Fe from soil contamination Figure 2. Linear increase in manure WEP:TP as manure TP concentration increased.0.500.400.00.200.100.00Manure WEP:TP0.00 0.10 0.20 0.0 0.40 0.50 0.60 0.70Manure % Py = 0.26x + 0.15Linear P < 0.01Quadratic P = 0.6Figure 1. Quadratic relationship between the concentration of P in the diet and the concentration of manure P collected from the pen surface. 0.700.600.500.400.00.200.100.00Manure % Total P (DM Basis)y = 8.08x2 = 1.872x + 0.00590.00 0.10 0.20 0.0 0.40 0.50 0.60Diet % P (DM Basis) Linear P < 0.01Quadratic P < 0.01Manure % Total P vs. Diet % Pto cause a reduction in WEP:TP of manure by as much as 48%. The com-bined effects of the many positively charged ions in soil, when mixed with manure P from hoof action on the pen surface, may form immobilized phosphate compounds that are not water soluble. Runoff events may remove propor-tionally more WEP than TP. However the loss of P in runoff from feedlot pens was less than 5% of excreted P. Back calculating manure P solubil-ity to account for a 5% loss (all in WEP form) of manure TP increased manure WEP:TP .9 units. The calcu-lated manure WEP:TP becomes 0.28 instead of the analyzed value of 0.24. However, this value is still less than the fecal WEP:TP value of 0.41. In addition, when urinary P is added to fecal WEP, the resulting mix of urine and feces is expected to be 0.52 WEP:TP. This expected value is 24 units of solubility higher than the actual value. These results showed the mix-ing of fecal and urinary P with soil contamination on feedlot pen surfaces reduced the WEP:TP of the resulting manure. When interpreting the results from this study for commercial feedlots, the reader is cautioned that the minimum and average TP values for feces and manure are influenced by data collect-ed from cattle fed experiment diets containing lower P (as little as 0.10% diet DM from diets containing corn bran and grits) than industry.1Virgil R. Bremer, graduate student; Crystal D. Buckner, research technician; Galen E. Erickson, associate professor; and Terry J. Klopfenstein, professor, Animal Science, Lincoln.

Total and Water Soluble Phosphorus Content of Feedlot Cattle Feces and Manure

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Total and Water Soluble Phosphorus Content of Feedlot Cattle Feces and Manure

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