Paper No. 7
Presentation Time: 10:05 AM
TRACE ELEMENT COMPOSITION OF BOVINE MILK IN KANSAS AND NEBRASKA
To determine the importance of variability in the geographic distribution of soil elements on the trace element composition of bovine milk in Kansas and Nebraska, milk samples from on-farm bulk storage tanks from dairies in Kansas and Nebraska were analyzed using inductively coupled mass spectroscopy and compared to environmental selenium concentrations derived from interpolated soil and sediment element concentrations. The analyzed elements included Ag, Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Tl, V and Zn. The milk concentrations of most elements in bovine milk did not exhibit a high degree of variability. Se, however, was an exception. The average selenium concentration in milk from bulk tanks was 56.1 µg/l, with a median of 52.1 µg/l, a standard deviation of 20.4 µg/l, a maximum of 109 µg/l, and a minimum of 23 µg/l. A Global Moran's estimate indicated that milk selenium was weakly spatially auto correlated in the study region (Moran’s I = 0.350; Z-score = 3.174; P = 0.001). Milk Se concentrations were also weakly correlated with interpolated soil and sediment Se concentrations, as indicated by a Spearman rank order correlation of 0.383 (P = 0.0001). Se exposures from soil and sediments are expected to be confounded by Se exposures from water and feed. Although these data suggest that there may be a local environmental influence on milk Se concentrations, studies that include local samples of soil/sediment, water and feed Se concentrations are therefore needed to characterize and quantify the extent of influence from various Se sources on milk Se concentrations. Exceptionally high Se concentrations, as found in some locations in the study region, may result in selenium intakes that approach levels associated with chronic selenosis in infants who use local bovine milk as their primary source of nutrition. Se concentrations in milk towards the higher end of the spectrum are, however, generally desirable from a nutritional perspective.