Analysis of Animal Feed Ingredients and Soil Amendment Products Produced from Beef Cattle Manure for Selected Trace Metals Using Atomic Absorption Spectrophotometry

Abstract

Beef cattle manures have been converted to a water slurry and subjected to centrifugation, flocculution and drying to produce a silage replacement product (CI), a 20% protein powder from the centrifuge supernatant fluid (CII) and a soil amendment product (CIII). These products and the manure slurry were analyzed for their As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn content by atomic absorption spectrophotometry. Different sample mineralization techniques, metal recovery efficiencies and matrix effects were investigated. Metal concentrations increased in the products in the order of silage replacement, protein and soil amendment. Except for a high iron concentration, the silage replacement product (CI) had concentrations of these metals comparable to those for typical feedlot rations, and metal concentration in the protein fraction (CII) was three to six times higher as compared to the range of metal levels in CI; the soil amendment product (CIII) showed metal concentrations comparable to reported manure values. The effects of these metal concentrations on utility of the silage replacement and protein products as feed ingredients for animal feed rations is discussed.