The objective was to evaluate EDXRF for measuring mineral concentrations in feeds and mixtures. When an X-ray tube radiates a sample, secondary X-ray photons are emitted with specific energies that generate spectral peaks related to individual elements. Heights of peaks can be calibrated to calculate element concentrations. Calibration samples included 20 TMR, 10 corn grain, 10 corn silages, 12 legume and 8 grass forages that were analyzed for Ca, P, Mg, K, Na, Fe, Mn, Zn, and Cu by ICP; S by combustion analysis; and Cl by titration. Typically, samples are finely ground (0.2 mm) and pelleted for EDXRF, but for this evaluation samples were ground through a 1.0 mm screen in a cyclone mill and 5 g of loose powder was placed in a 40-mm cup and covered with 3.0-um Prolene film before scanning for 9 min. The EDXRF instrument was a Bruker S2 PUMA with SPECTRA.ELEMENTS software used for calibration. Elements Na, Mg, P, S, and Cl were measured with 20 kV and no filter, and K, Ca, Mn, Fe, Cu, and Zn were measured with 40 kV and a 500-µm Al filter. Tube current was automatically adjusted. Mineral concentration ranges were typical for feeds and mixtures. High R² and low standard deviation of linear regression (SD) in the table indicate excellent agreement between analytical and EXDXRF results at selected peaks. Instrument precision was excellent when the same sample was scanned 10 times. When scanning time was reduced to < 5 min, there was a small loss in precision and accuracy. The results (Table 1) indicate that using EDXRF with routine feed sample preparation offers an excellent alternative for mineral analysis in feeds and mixtures. Table 1.

Element	n	Range (in DM; %)	R2	SD	Peak (keV)	Precision (%)
Ca	58	0.01 to 2.65%	0.986	±0.07%	3.696	±0.01%
P	57	0.15 to 0.60%	0.959	±0.02%	2.016	±0.00%
Mg	60	0.09 to 0.53%	0.941	±0.03%	1.251	±0.01%
S	53	0.10 to 0.48%	0.974	±0.02%	2.311	±0.00%
K	54	0.35 to 3.91%	0.994	±0.07%	3.302	±0.00%
Cl	51	0.00 to 1.88%	0.993	±0.026%	2.635	±0.00%
Na	60	0.01 to 0.72%	0.942	±0.05%	1.047	±0.01%
Fe	57	20.8 to 1821 ppm	0.994	±26.0 ppm	6.400	3.50 ppm
Mn	58	4.61 to 138.3 ppm	0.963	±7.11 ppm	5.895	±1.04 ppm
Zn	60	13.4 to 133.5 ppm	0.986	±3.47 ppm	8.632	±1.71 ppm
Cu	59	1.23 to 24.9 ppm	0.956	±1.35 ppm	8.044	±0.44 ppm